Contents lists available atScienceDirect
Journal
of
Plant
Physiology
j o u r n a l h o m e p a g e :w w w . e l s e v i e r . c o m / l o c a t e / j p l p h
Physiology
Regulation
of
cell
wall
remodeling
in
grapevine
(Vitis
vinifera
L.)
callus
under
individual
mineral
stress
deficiency
João
C.
Fernandes
a,
Luis
F.
Goulao
b,
Sara
Amâncio
a,∗aDRAT/LEAF,InstitutoSuperiordeAgronomia,UniversidadedeLisboa,TapadadaAjuda,1349-017Lisbon,Portugal
bBioTrop,InstitutodeInvestigac¸ãoCientíficaTropical(IICT,IP),PóloMendesFerrão—TapadadaAjuda,1349-017Lisbon,Portugal
a
r
t
i
c
l
e
i
n
f
o
Articlehistory:
Received17August2015
Receivedinrevisedform22October2015
Accepted22October2015
Availableonline1December2015
Keywords:
Cellwallpolymers
Endoglucanaseactivity
Geneexpression
Nutrientdeficiency
Pectindesterification
a
b
s
t
r
a
c
t
Cellwall(CW)isadynamicstructurethatdeterminestheplantform,growthandresponseto envi-ronmentalconditions.Vitisviniferacallusgrownundernitrogen(−N),phosphorous(−P)andsulfur(−S) deficiencywereusedasamodelsystemtoaddresstheinfluenceofmineralstressinCWremodeling. Calluscellsmorphologywasaltered,mostlyunder–N,resultinginchangesincelllengthandwidth comparedwiththecontrol.CWcompositionascertainedwithspecificstainingandimmuno-detection showedadecreaseincelluloseandalteredpatternofpectinmethylesterification.Undermineralstress genesexpressionfromcandidatefamiliesdisclosedmainlyadownregulationofaglycosylhydrolase family9C(GH9C),xyloglucantransglycosylase/hydrolases(XTHs)withpredictedhydrolyticactivityand pectinmethylesterases(PMEs).Conversely,upregulationofPMEsinhibitors(PMEIs)wasobserved.While methylesterificationpatternscanbeassociatedtoPME/PMEIgeneexpression,thelowercellulosecontent cannotbeattributedtoalteredcellulosesynthase(CesA)geneexpressionsuggestingtheinvolvementof othergenefamilies.Saltextractsfrom–Nand−Pcallustissuesincreasedplasticdeformationin cucum-berhypocotylswhilenoeffectwasobservedwith−Sextracts.Thelowerendo-actingglycosylhydrolase activityof−Ncallusextractspinpointsamoreexpressiveimpactof−NonCW-remodeling.
©2015ElsevierGmbH.Allrightsreserved.
1. Introduction
Theprimaryplantcellwall(CW)isadynamicstructureformed bya complex ofinextensible cellulosemicrofibrils bonded toa network of coextensiveglycans embedded in a pectin-rich gel matrixthatincludesstructuralglycoproteins,phenoliccompounds andenzymes.CWplaysavitalroleincontrollingthecellshape and,consequently,itsmorphology(Doblinetal.,2010;Cosgrove andJarvis,2012).Well-orchestratedCWalterationsresultingfrom synthesis, disassembly,solubilizationand rearrangements ofits
Abbreviations:2,4-D,2,4-dichlorophenoxy-aceticacid;CesA,cellulosesynthase;
CMC,carboxymethylcellulose;CW,cellwall;EXP,expansin;EXPA,␣-expansin;
GalA,galacturonicacid;GH9A,glycosylhydrolasefamily9A;GH9C,glycosyl
hydro-lasefamily9C;HG,homogalacturonan;KOR,KORRIGAN;−N,absenceofnitrogen;
−P,absenceofphosphorous;PBS,phosphatebufferedsaline;PG,
polygalactur-onase;PL,pectatelyases;PME,pectinmethylesterase;PMEI,pectinmethylesterases
inhibitor; PVP-40T, polyvinylpyrrolidone; −S, absence of sulfur; XEH,
endo-hydrolaseactivityofxyloglucantransglycosylase/hydrolases;XET,transglycosylase
activityofxyloglucantransglycosylase/hydrolase;XTH,xyloglucan
transglycosy-lase/hydrolase;XyG,xyloglucan.
∗ Correspondingauthor.
E-mailaddress:samport@isa.ulisboa.pt(S.Amâncio).
structuralcomponentsand linkages,arethebasisofcell expan-sionandgrowth.Moreover,CWsrepresentoneofthefirstlevelsof communicationbetweentheplantandsurroundingenvironment, playingadecisiveroleinadaptationtobioticandabioticpressures (LandreinandHamant,2013;Malinovskyetal.,2014;Tenhaken, 2015).CWchangesrelatetoeventssuchaslocalizedcelldivision, arrestmentofcellelongationandalterationsindifferentiation sta-tus,resultinginconstraintsthatimpactchangesinanatomyand development(Pottersetal.,2007;Braidwoodetal.,2014).
ThemolecularregulationunderlyingCWdynamicbehavior out-comesparadoxaleffectsinthecontributionprovided tothecell mechanical properties. Growingcells expand by CW loosening while, at thesame time, enoughstrength is kept toretain the integrity and withstand highturgor forces. The control of CW loosening hasbeenpostulatedtooccur, atleast inpart,due to modificationsinthecellulose-xyloglucan(XyG)networklinkages (McQueen-MasonandCosgrove,1995;Cosgrove,2000;Whitney etal.,2000),wasprovedbyVanSandtetal.(2007).RecentlyPark and Cosgrove(2012,2015) proposedthat XyGisrestrictedtoa minorcomponentoftheCW,closely intertwinedwithcellulose atlimitedsites,promotingselectivetargetsforCWloosening,the socalled“biomechanicalhotspots”theory.Othermodificationsin the same network as wellas in the pectin structure can, con-http://dx.doi.org/10.1016/j.jplph.2015.10.007
versely,resultinCWstiffeningandsuppressionofcellelongation (Takedaetal.,2002),alsocontributingtoCWintegrityandrigidity. Infact,hydrolysisofmethylesterbondsatGalAresidues,leading toalterationsinlinearhomogalacturonan(HG)domains,degree andpatternofpectinmethylesterification,significantlyimpacts CWbiophysicalproperties(Peaucelleetal.,2008,2011;Jolieetal., 2010).
TheroleofCW synthesisand modificationhasbeen investi-gatedthroughquantificationofrelatedenzymeactivityandgene expressionandtheenzymebiologicalfunctionhasbeendisclosed ingenotypesimpairedoroverexpressingspecificgenemembers (e.g.,Osatoetal.,2006;Peaucelleetal.,2008;Miedesetal.,2010). Inknocked-outcellulosesynthase(CesA)Arabidopsisthaliana mutantsaneffectivereductionincellulosecontentwasobserved togetherwithmoderateabnormalgrowth(Desprezetal.,2007; Handakumbura et al., 2013)confirming other resultson CesAs requirementforcellulosesynthesis(Somerville,2006;Endlerand Persson,2011).Nonetheless,CesAactivityisinsufficientto guar-anteethecorrectformation ofthenetwork suggesting thatthe coordinatedparticipationofothercomponentsisneededfor cel-lulosesynthesis,assemblageordeposition(Takahashietal.,2009). MutationsimpairingtheexpressionofKORRIGAN(KOR),aclassA -1,4-endo-glucanase(GH9A)(Urbanowiczetal.,2007a), demon-strate the requirement of KOR for the correct assemblage in elongatingcells(Nicoletal.,1998)sincetheyshowasignificant reductionincellulosecontentevenwhentheexpressionofallCesA memberswasnormal.Thisreductionwasapparentlycompensated withincreasedpectinamountsand alteredcomposition, partic-ularlyanincreasedglucosecontent(Satoetal.,2001).Recently Vainetal.(2014)showedthatKORisanintegralpartoftheCesA complex.AroleforapoplarclassC-1,4-endo-glucanase(GH9C) memberinmodulatingcellulosecrystallinityanditsinvolvement incellgrowthwasrecentlydemonstratedusingreversegenetic approaches(Glassetal.,2015).
RegardingCWremodeling,expansins(EXP),proteinswiththe abilitytocauselooseningininvitroassays(McQueen-Masonetal., 1992),areconsideredthemajorcontributors,actingbyreversible weakeninginteractions or disrupting hydrogen bondsbetween cellulosemicrofibrilsandmatrix-linkedglycans(McQueen-Mason andCosgrove,1995;Cosgrove,2000;Whitneyetal.,2000;Wang etal.,2013).Amongtheexpansinsuperfamily,␣-expansins(EXPA) aretheforemostpromotersincontrollingcellextensibilityindicots (Cosgrove,1999,2000).AsreviewedbyChoietal.,(2006),genetic modificationallowedassociatingEXPAstocellenlargementand fruitsoftening amongothereffects onplantgrowthand devel-opment. Other members of CW enzyme families were further demonstrated to cause CW extensibility under in vitro condi-tions,namelysomexyloglucanendotransglycosylases/hydrolases (XTHs)(VanSandtetal.,2007)andendoglucanases(GHs)(Yuan etal.,2001;ParkandCosgrove,2012).Tomatohypocotyls over-expressingorsuppressedinaspecificXTHproducedrespectively increasedanddecreasedlevelsofsolubleXETactivity,anda pos-itive correlation with CW extensibility and organ growth was observed(Miedesetal.,2010).WithaspecificArabidopsis RNAi-silencedXTHOsatoetal.(2006)obtainedasmallbutsignificant reductionin primaryroot cellelongationrecentlyconfirmed in Wilsonet al. (2015) using multi-omics analysis. Similarly, also in Arabidopsis, the down-regulationof a specificclass C -1,4-endo-glucanase(GH9C)ledtoweakeningoftheCWduringroot hairformationandgrowth(delCampilloetal.,2012).The regu-lation,patternandextentofpectinde-esterificationiscontroled bytheactivityofparticular membersofpectinmethylesterases (PMEs)(reviewedbyGoulao,2010)andtheirinteractionwith spe-cificinhibitors(PMEI)(Bellincampietal.,2004;DiMatteoetal., 2005; Juge, 2006; Jolie et al., 2010) and therefore, are among themain enzymesto impactchanges in biophysical properties
of the CW. It is proposed that depending onthe specific pat-ternanddegreeofmethylesterification,pectinscanaggregateinto hydratedcalcium-linked gelstructures, that increase wall stiff-ness and reduce creep (Willats et al., 2001), or make pectins moresusceptibletodepolymerisationbypolygalacturonases(PGs) andpectatelyases(PLs)hydrolysiscontributingtoCWrelaxation (BrummellandHarpster,2001;Wakabayashietal.,2003).In Ara-bidopsismutantsover-expressingaPMEoraPMEI,Peaucelleetal. (2008,2011)observedrespectively,decreasedandincreasedpectin methylesterification,suggestingCWlooseningisgeneratedbyPME activity. This assumption was confirmed in other works using ArabidopsismutantsimpairedinPMEactivitywithevidenceof inhi-bitionofcellelongation(Derbyshireetal.,2007)andreductionin thedegreeofmethylesterification(Hongoetal.,2012).Modelsof CWarchitecturearesupportedbyevidencesforthepresenceof covalentbondsbetweenpectinchainsandcellulosemicrofibrils (Zykwinskaetal.,2005,2007;ParkandCosgrove,2015)or matrix-linkedglycans(PopperandFry,2005;Marcusetal.,2008)disclosing importanttiesinCWbiochemistryandanunder-lookedroleplayed byPMEsand PMEIsinCW mechanicalproperties.Furthermore, underconditions thatdrasticallycompromise theCW integrity, plantcellsareknowntotriggercompensatoryalternative mech-anismstoitsreinforcementviabiosynthesisofnewmaterialor establishmentofnewlinkages(PillingandHöfte,2003;Wolfetal., 2012),addingadditionalcomplexitytothefine-tunedprocessof CWresponsestodevelopment-impactingstimuli.
UsingVitisviniferacallusasamodelexperimentalsystemwe recentlyshowedthatindividualmineraldeprivationleadstoCW structuralmodifications (Fernandes etal.,2013), inparticular a decreaseincellulosecompensatedbyanincreaseinlignincontent, andmodificationsinpectinmethylesterification.Thissuggestsa specificlevel of controlto producea complex fine-tuned sens-ing mechanism tomaintain CW integrity. Plant CW-modifying enzymesarepresentinlargemultigenicfamilies(Lerouxeletal., 2006; Farrokhi et al., 2006), involving more than 2000 genes (Carpitaetal.,2001)withdistinctpatternsofexpressionamong cellsandtissues.
ToextendourpreviousresultsontheCWspecificcomposition andarrangementmodificationsinresponsetoindividualmineral deprivationatmolecularregulationlevel,acomprehensiveinsilico dataminingwasundertakentoretrievethesequenceofall iden-tifiedmembersofV.viniferacandidateCW-modifyingmultigenic familiesandtheexpressionofamplifiedsequencesincalluswas quantified.Thepotentialloosening activityofsalt extractsfrom callusgrowingunder mineraldeficiency wasaddressedand an extensometer-basedexperimentalapproachwasusedtoevaluate invivomechanicalmodificationsondicotCWspecimens.
2. Materialandmethods
2.1. Calluscultureandmineralstressimposition
CallustissuesestablishedfromV.viniferacv.TourigaNacional leaveswereobtainedasdescribedinJacksonetal.(2001).Four explantswithcirca4.5gtotalweightper9cmPetridishwere growinginMSbasalsaltsmedium(MurashigeandSkoog,1962) (DuchefaBiochemie, Haarlem, NL) supplemented with 2.5M 2.4-D(2,4-dichlorophenoxy-aceticacid);1Mkinetin;5gl−1 PVP-40T;20gl−1,sucrose;2gl−1Gelrite®,pH5.7,at25◦C,inthedark.
FollowingtheexperimentalconditionsdescribedinFernandesetal. (2013)callustissuewassub-culturedeverythreeweeks,foratotal of9weeks.Toobtainthesamplesunderimposedmineral defi-ciency(mineral stresses), fourtreatments were applied:(i) MS completemedium(control),and(ii)nitrogen(−N),(iii)phosphorus (−P),(iv)sulfur(−S)deficientmedia,inwhichnitrates,phosphates
and sulfateswerereplaced bychlorides. Aftereach three week culturecycleineachtreatmentmedium,samplescorresponding tothreePetridisheswerecollectedtomonitorgrowth.Basedon theresultsobtained,sixweeksgrowncallus(2×3weeks)were usedimmediatelyformicroscopystudiesorstoredat−80◦Cfor
subsequentextractionofproteinsaltextractsorRNA. 2.2. Histologicalstaining
SamplesofcallustissueweregentlydesegregatedinPBSbuffer andaddedwith2–3dropsof0.1%(w/v)CalcofluorWhite fluores-centbrightener(Sigma,St.Louis,MO)forcellulosedetection.The materialwasthentransferredtoamicroscopeslidewithacover slipandvisualizedwithaLeitzLaborluxSFluorescenceMicroscope underUVlight.ImageswereacquiredwithaZeissAxioCam digi-talcamera.Pecticpolysaccharideswerestainedaccordingtothe sameprocedure,butinthiscase,Calcofluorwasreplacedby2–3 dropsof1%(w/v)ToluidineBlueandtheslideswereobservedunder lightmicroscopy.CellsweremeasuredusingtheCarlZeissVision AxioVisionViewer4.
2.3. Immunolocalizationwithmonoclonalantibodies
Callus were gently desegregated and equilibrated in 5% dry milk/PBSfor30minatRTandthenincubatedovernightat4◦Cwith a10-folddilutionof2F4orPAM1antibodies(Linersetal.,1989; Willatsetal.,1999)dilutedin5%w/vnon-fatdrymilk/PBS.After extensivewashingwithPBS,a30-folddilutionofthesecondary antibody(anti-mouseIgGandanti-ratIgG(Sigma),respectively) wasappliedtothesectionsandlefttoincubatefor60mininthe dark.Fornegativecontrolstheprimaryantibodieswereomitted. TheslideswerethenwashedwithPBSandbrieflyincubatedwith 1%(w/v)CalcofluorWhiteindistiledwater,rinsedandmounted onamicroscopeslide.SectionswereobservedwithaLeitz Labor-luxSFluorescenceMicroscopeandimageswereacquiredusinga ZeissAxioCamdigitalcamera.TheImagesweresuperimposedand analyzedusingtheImageJ1.48package(http://imagej.nih.gov/ij/ ).Theaveragenumberofbluepixels(Calcofluor)andgreenpixels (PAM1and2F4)wasquantified.
3. Geneexpressionanalyzes
3.1. DatabaseminingandsequenceretrievalofV.vinifera CW-relatedgenes
Sequences from members of the CesA, EXPA, XTH, EGase from hereon referred as GH9 (http://www.cazy.org), PME and PMEI families were retrieved by multiple database searches for V. vinifera and three other model species with sequenced genomes,namelytalecress(A.thaliana),rice (Oryzasativa) and poplar(Populustrichocarpa).TheNCBI(http://www.ncbi.nlm.nih. gov/) and Genoscope 12X (http://www.genoscope.cns.fr/spip/) databaseswereusedforV.viniferagenesearcheswhileTAIR(http:// www.arabidopsis.org/index.jsp),OryGenesDG(http://orygenesdb. cirad.fr/cgi-bin/gbrowse/odbjaponica/?name=Os1:1..10000)and Phytozome (http://www.phytozome.net/poplar)wereminedfor Arabidopsis, Oryza and Populus, respectively. In each case, after identificationoftheaminoacidsequence,thesamedatabasewas minedforeachhittoretrievethefull-lengthcDNAsequenceofthe predictedcorrespondinggene.V.viniferasequenceswerenamed accordingtotheirsimilaritywithArabidopsisorthologous. After prediction(SignalP4.0;Petersenetal.,2011)andremovalof sig-nal peptides from the amino acid sequences, alignments were performedusingMUSCLEsoftware(Edgar,2004a,b)andcurated by Gblockssoftware (Talavera and Castresana,2007).The den-drogramswereconstructedusingPhyML(Guindonetal.,2010),
andviewedusingTreeDynsoftware(Chevenetetal.,2006). Puta-tivebiological activitywasinferredfromamino acidsequences using InterProScan 5 (http://www.ebi.ac.uk/Tools/pfa/iprscan5/; Quevillonet al.,2005.Tertiary structure-modelswerepredicted usingthealignment-basedmodelingtoolsSWISS-MODEL(http:// swissmodel.expasy.org/;Arnoldetal.,2006)andSwisspdbViewer DeepView4.0(http://www.expasy.org/spdbv/;GuexandPeitsch, 1997).
3.2. RNAextractionandcDNAsynthesis
TotalRNAwasextractedfromV.viniferacallususingthemethod describedbyReidetal.(2006).RNAsampleswerefurthertreated withRNase-freeDNaseI(Qiagen)accordingtothemanufacturer protocol.QuantificationwascarriedoutinaSynergyHTMultiplate Reader,withGene5software,usingaTake3TMMulti-VolumePlate
(Bio-TekInstrumentsInc.,Winooski,USA).Forreverse transcrip-tion,theRevertAidreversetranscriptaseprimingwitholigo-d(T) kitwasused(ThermoScientific)accordingtothemanufacturer’s recommendations.
3.3. Quantificationofgeneexpressionbyquantitativereal-time PCR(RT-qPCR)
For each V. vinifera cDNA sequence retrieved, a set of spe-cificprimersweredesigned(TableS1)andusedtoamplifycallus grapevinecDNAresultingfromthetranscriptionof2goftotal RNA, using conventional PCR and gel agarose electrophoresis. Whenamplificationwasobserved,confirmingtheexpressionin callustissues,thetranscriptswerequantifiedbyreal-timePCR (RT-qPCR),performedin20LreactionvolumescomposedofcDNA derivedfrom2gRNA,0.5Mgene-specificprimers(TableS1) inSsoFastTMEvaGreen®Supermixes(Bio-Rad,Hercules,CA)using
aiQ5Real-TimeThermalCycler(BioRad,Hercules,CA).Reactions conditionsforcyclingwere:9◦Cfor3minfollowedby40cyclesof 9◦Cfor10s,61◦Cfor2sand2◦Cfor30s.Meltingcurveswere gen-eratedineachcasetoconfirmtheamplificationofsingleproducts andabsenceofprimerdimerization.Eachanalysiswasperformed intriplicatereactionsofthreebiologicreplicates.The correspond-ingquantificationcycles(Cq)weredeterminedbytheiQ5optical
systemsoftware(Bio-Rad,Hercules,CA)andexportedtoaMSExcel spreadsheet(MicrosoftInc.,CA)forfurtheranalysis.Cqvaluesof
eachgeneofinterestwerenormalizedwithrespecttoactin(Act) andtranslationinitiationfactoreIF-3subunit4(TIF)Cqs(Coitoetal., 2012).Relativegeneexpressionvaluesintheabsenceofagiven nutrient(−N,−P,−S)arepresentedaslog2fold-changevaluesin
relationwiththecontrolconditions(C).HeatMapwasperformed withPearsoncorrelationsusing theMeV software(Saeedetal., 2003).
4. EvaluationofcallussaltextractpotentialtoinduceCW extensibility
4.1. Preparationofsaltextracts
Samplesof20g(FW) V.viniferacallustissuesgrowingunder eachexperimentalconditionwerecutintosmallpiecesandwashed with20mMNaOAcpH4.5buffer.Thewashedcallussampleswere filteredbyvacuumandtheflowthroughswerediscarded.Twenty millilitersofa20mMNaOAc;1MKClpH4.5solutionwerethen addedtothecallusandthemixtureswereincubatedfor30min at4◦C,filteredandeachsolutionwasconcentratedto1mlusing AmiconUltraUltracell3Kcolumns(Millipore)asperthe manu-facturer’srecommendationsanddesalinizedwithPD-10desalting columns(cut-off5kDA)(GE,Fairfield,USA).Proteinineach callus-derivedextractwasquantifiedusingtheBradford(1976)method
withBSAasstandard.Thesameextractswereevaluatedforability toinduceextensibledeformationincucumberhypocotylsections, takenasmodelfordicotCWspecimens,andtestedfor -1,4-endo-glucanaseactivity.
4.2. Extensibilityassays
Cucumberseedsweresownat25◦C,inthedarkandgerminated hypocotylapicalzones(3cm)werecutandstoredat−20◦C.Prior
totheanalyzes,thehypocotylscuticleswereabradedusing car-borundumpowderandsampleswereboiledfor1s.toinactivate endogenousenzymes.Thehypocotylswerethenassayedclapped totensiongripsin aTA-XTTextureAnalyzer(StableMicro Sys-temsLtd.,UK),usingacustommadeclampingreservoirfilledwith 50mMNaOAcpH4.5buffer.A20gloadtensileforcewasapplied witha 1.5mm test length betweenclampsand, after a 20min periodofextensionforequilibration,thebufferwasreplacedby eachsalineextractsolutionbeingtestedandassayedforadditional 15min.Theforcewasthenremovedduring10minandreapplied for additional 20min, to allowcalculation of Total, Plastic and Elasticextensibilities(Cosgrove,1993).Totalextensibilitywas cal-culatedasthemaximumhypocotyllengthatconstantload.Plastic extensibilitywascalculatedastheminimumvaluereachedafter forceremoval.Elasticextensibilityisthedifferencebetweenthe totalandplasticextensibility(Richmondetal.,1980).Each experi-mentwasperformedusingatleast6independentsamplesforeach treatment.
4.3. ˇ-1,4-Endo-glucanaseactivity
Endo-actingglycosyl hydrolaseactivitywasmeasuredbythe changeinviscosityofa carboxymethylcellulose(CMC)(medium viscosity,Sigma)solution(DurbinandLewis,1988).Onehundred microlitreofeachsaltextract,ataconcentrationof3gl−1,were
addedto350mlofa1.5%(w/v)CMCsolutionin20mMphosphate bufferpH6.0,incubatedfor6hat37◦C.Viscositywasdetermined bymeasuringthetimetaken forthemovement ofthemixture throughthe0andthe0.05mlmarksofa0.1mlglasspipettefixedin averticalpositionusingastopwatch.Readingsweretakenattime 0h,2hand6hintriplicates.Activityisreportedasthedecreasein viscosity(%)withrespecttotimezero.
4.4. Statisticalanalysis
Alldataispresentedasmeanvalues±standarddeviation(SD)of anappropriatenumberofreplicatesineachassay.Theresultswere statisticallyevaluatedbyvarianceanalysis(ANOVA)andposthoc Bonferronitestwithap<0.05tocomparethesignificanceofeach treatmenteffect.The SigmaPlot(Systat SoftwareInc.)statistical packagewasused.
5. Results
5.1. Callusgrowthin−N,−Pand−SandfullMSmedium
TheeffectoftheimposedindividualmineralstressesontheVitis calluswasassessedbymeasuringthecallusgrowthalong time. Afterwithdrawingofnutrients,therelativegrowthofthecallus wassignificantlyaffectedinthethreecycleswhencomparedtothe control(Fig.S1).Afterthefirstcycle,−Ncalluscellswerethemost affected;attheendofthesecondcyclethethreemineralstresses severelyaffectedcallusgrowthimpairingtheirviabilitythereafter. So,sixweeksoldcalluswereselectedforsubsequentanalyzes.
Supplementrymaterialrelatedtothisarticlefound,intheonline version,athttp://dx.doi.org/10.1016/j.jplph.2015.10.007.
Table1
MeasuredlengthandwidthofV.viniferacalluscellsaftersixweeksgrowthin
com-pletenutrientmedium(control),andintheabsenceofnitrogen(−N),phosphorus
(−P)andsulfur(−S).Valuesarethemean±SDof20randomcells.Differentletters
ineachrowindicatesignificantdifferencesatp<0.05.
Control −N −P −S
Length(m) 121.0a±12.1 228.7b±38.9 147.9c±19.1 130.5a±13.3
Width(m) 48.6a±3.5 47.2a±2.7 49.4b±2.0 48.1a±3.2
5.2. Cellmorphologyinresponsetomineraldeficiencies
Afirstindicationoftheeffectofstressimpositioninthe
cal-lustissuesusingthebiologicalsystemusedwasgainedthrough
measurementofcellanatomicalparameters.Exceptforsulfur,the
absenceofindividualmineralsproducedchangesinthe
morphol-ogyofV.viniferacalluscells(Table1).Noticeably,thedeprivationof
eachmineraleffecteddifferentalterationstothecellmorphology. Undernitrogenstarvationthecellswerelongerbuthadasimilar width,whencomparedwiththecontrol.Ontheotherhand,under phosphorusdepletionthecells werelongerand widerthanthe control,althoughstillshorterthanunder−Nconditions(Table1). 5.3. InsitulocalizationofcallusCWpolymersandepitopes
CalcofluorWhite wasusedtodetectCW matrix polysaccha-rideasitreadilybindstocellulose.Theabsenceofmineralsinthe mediumresulted,inallcallustissues,inareducedintensityof Cal-cofluorlabeling.Thisreductionwasmorepronouncedinsamples producedundernitrogenstarvation(Fig.1;TableS2).Toluidine Bluebindstocarboxylatedpolysaccharidessuchaspectins, produc-ingareddishpurplestaining.AsobservedinFig.1,intheabsenceof nitrogenamoreintensestainingoccurs.Immunolocalizationwith monoclonalantibodiestargetedtospecificCWepitopesisauseful tooltoanalyzeinvivodetailedlocalizationofCWcomponentsand wasemployedtoascribeputativemodificationsintheCW com-positioninresponsetotheimposedstresses,targetingdifferences inmethylesterificationpatterns.ThecombineduseofCW-epitope antibodiesandhistologicaldyesenabledustogainmoredetailed informationregardingdifferencesinthepecticcomposition.The resultsshowthat,under–Nand–Sconditions,anincreasein2F4 labeling,anantibodythatrecognisesdimericassociationof pec-ticchainsthroughcalciumions,isobservedinthewholecell,being moreprominentinthemiddlelamella(Fig.1;arrows).Ontheother hand,PAM1,whichrecognizesepitopesoflongun-esterifiedblocks ofGalAresidues,didnotbindtotheboundariesofthecellin−Nand −Scallustissues,whileitwasclearlynoticeableinthesespecific regionsincellsofcallusgrowingunderfullnutrientsandfaintly under−Pconditions(Fig.1;arrow;TableS2).
6. ChangesingeneexpressionofCW-relatedfamilies
6.1. Insilicoanalyzes
TheinitialapproachwastoevaluatetherelationshipofCW syn-thesisandmodificationcandidategenefamiliesbetweenV.vinifera andannotatedgenesinotherfloweringspecies.Insilicoanalysis showedthat,ingeneral,theV.viniferagenomehasasimilarnumber ofmemberstoArabidopsis,OryzaandPopulusforCW-relatedgene familiesthatactoncellulose-hemicellulosecomplexes(Table2).V. viniferaandO.sativashowedasignificantlylowernumberofPME membersidentifiedinthedatabasesthantheothertwospecies usedforcomparison.Ontheotherhand,thenumberofPMEIs var-iedaccordingtoeachindividualspecies,beinglowerinA.thaliana(6 members)andhigherinO.sativa(13members).Itshouldbe how-evernotedthatdatabaseminingdidnotdifferentiatetruePMEI
Fig.1.Histologicalstainingforcelluloseandpecticpolysaccharidesandimmunolocalizationof2F4andPAM1reactivehomogalacturonanepitopesincallusgrownunder
controland−N,−Pand−Sconditions.ImmunolocalizationsampleswerealsostainedwithCalcofluorWhitetorevealanatomicaldetails.2F4andPAM1signalsareshown
ingreen.Nolabelwasobservedwhenprimaryantibodieswereomittedfromcontrolsections(Fig.S2).ThephotostakenforCalcofluorWhite,2F4andPAM1havethesame
expositiontimeforalltreatments.Barscaleforhistologicalobservationsrepresents50m(and)and10mforimmunolocalizationof2F4andPAM1.
Table2
NumberofgenesrelatedtoprimaryCWbiosynthesisandmodificationretrieved
insilicofromthehigherplantsequencedspeciesVitisvinifera,Oryzasativa,Populus
trichocarpaandArabidopsisthalianagenomes.
Vitis vinifera Arabidopsis thaliana Oryza sativa Populus trichocarpa CesA 10 10 10 18 Expansinsuperfamily 30 36 56 36 XTH 33 33 29 24 GH9 21 25 24 31 PME 36 66 37 84 PMEI 11 6 13 10
frominvertaseinhibitors.AhighernumberofEXPAs(53members)
wasretrievedfromtheO.sativagenome.
Thedendrogramsbuiltwithaminoacidsequences,revealsthat,
ingeneral,V.viniferaCW-relatedsequencesclusterwithorthologs
frommonocot,dicotandwoodymodelspeciesinmostfamilies
(Figs. S3–S5). Noticeably, in the XTH family, some clustersare
enrichedwithV.viniferasequences.
Supplementrymaterialrelatedtothisarticlefound,intheonline
version,athttp://dx.doi.org/10.1016/j.jplph.2015.10.007.
SinceXTHgenesencodeproteinsthat canhavetwo distinct catalytic activities, sequence alignments and structural insilico analysiswereperformedtodistinguishputativexyloglucan endo-transglucosylases (XET) from xyloglucan endohydrolases (XEH) (Fig.S6).TheXTHidentitywasconfirmedbythepresenceinall V.viniferasequencesoftheconservedcatalyticmotif (W/R)-(D/N)-E-(I/L/F/V)-D-(F/I/L/M)-E-(F/L)-(L/M)-G,aspreviouslydescribedby EklöfandBrumer,(2010)andXETorXEHputativeactivitieswere assignedbasedonthepresence/absenceoftwoinsertions, (Y/N)-P-GandR-(I/L)-I-G-R(Fig.S7)intheaminoacidsequence(Eklöfand Brumer,2010).Basedonthesestructuraldifferences,twoisoforms, VviXTH31(XP002275862)andVviXTH32(XP002269285),were identified.Despitetheinsertions,thestructuralsimilaritybetween XETandXEHwasfoundtobeveryhigh,asindicatedbythe
super-impositionoftheirbackbones(Fig.S6).Themaindifferenceoccurs betweenspecies,especiallyintheC-terminusinwhichan␣-helix isobservedbothinTropaeolummajusandArabidopsisbutisabsent inV.vinifera.
Supplementrymaterialrelatedtothisarticlefound,intheonline version,athttp://dx.doi.org/10.1016/j.jplph.2015.10.007.
Likewise,PMEIssharestructuralpropertieswithotherinvertase inhibitorsanditsclassificationwasproposedtobepossiblebased ontheconformationfeaturesofanextensionthatprecedesa four-helixbundlecore(Scognamiglioetal.,2003).We noticedahigh similaritybetweenV.viniferaandArabidopsisPMEI,whichshowed similarextension(Fig.S8).
Supplementrymaterialrelatedtothisarticlefound,intheonline version,athttp://dx.doi.org/10.1016/j.jplph.2015.10.007.
6.2. Changesinexpressionofkeygenesinvolvedinthe biosynthesisandmodificationofCWundermineralstress
Onewayoftacklingthepathwaysofagivenphysiologicalevent istounderstandthetranscriptionofrelatedgenes.Thus,isoformsof severalgenefamilies(TableS1)werechosenbasedontheirputative roleinthesynthesisandmodificationofCWafternutrient starva-tion.Fiftyoutofthe131genesinvestigated(38.2%)expressedinthe callustissueandtheirexpressionlevelwasquantifiedbyRT-qPCR asshowninFigs.3and4 inTableS3withmoredetail.
Supplementrymaterialrelatedtothisarticlefound,intheonline version,athttp://dx.doi.org/10.1016/j.jplph.2015.10.007.
Althoughasimilarnumberofgeneshadbeenup-and down-regulatedinresponsetoindividualmineralstressimposition,the majorityofthemweredownregulatedinalltreatments(Fig.2). Seven showed up-regulation in all stress conditions (VviCesA2, VviEXP8, VviXTH8, VviXTH10, VviPMEI2,VviPMEI3 and VviPMEI4) (Fig.2a),while16weredown-regulatedinalltreatments(VviCesA4, VviXTH32, VviGH9A1,VviGH9C2, VviXTH2, VviEXP5, VviEXP3, Vvi-EXP11,VviXTH15,VviPME1.17,VviPME1.18,VviPME1.19,VviPME2.4,
Fig.2.Venndiagramsummarizingthenumberofuniqueandcommongenesshowingdifferenttrendsofgeneexpression,up-(A)ordown-regulated(B),inresponseto
eachindividualmineralstressimposed(−N,−Pand−S),whencomparedtocontrolconditions.Inbraketsisthenumberofgeneswithmorethantwofoldchange.TheVenn
diagramwasdrawnusingtheVennyTool(Oliveros,2007).
VviPME2.7,VviPME2.14,VviPME2.20)(Fig.2b).Thenumberofgenes withdetectedaltered expressionwasalwayshigherin−N, fol-lowedby−Pandlowerin−Scallussampleswhich,asshowedby hierarchicalclustering(Fig.3)indicatesthatsamplesfrom−N cal-lustissueshavemoreuncorrelatedtranscriptionpatternsthanthe samplesobtainedundertheothertwoconditions.
Concerningthegenesstudiedthatcanbeputativelyassociated withcellulosebiosynthesis,theresultsdisclosedtheup-regulation ofoneCesAgeneinresponsetonitrogen(VviCesA3)andphosphorus (VviCesA8)deficienciesinthegrowingmedium,andthreemembers inresponsetosulfur(VviCesA1-3)deprivation,whereasthe tran-scriptionofVviCesA6was3-foldrepressedunder−Sconditions. GH9A,whichareorthologoustoKORRIGANgenes,showednotto bedifferentiallyexpressedinresponsetothemineralstress imposi-tionbutaseverereductionof4.45and5.25fold-changeintheclass C,VviGH9C2,transcriptamountswasobservedinsamplesgrowing undernitrogenandsulfurdeficiency,respectively(Fig.3).
EXPAgeneexpressionwassimilarlyregulatedinresponseto nitrogenandphosphorusdeficiencies,asillustratedbythe down-regulation,inbothcases,oftwoisoforms,VviEXP6andVviEXP11 (TableS3).Transcriptionimpairmentofthosememberswas par-ticularly severe in –P conditions (Fig. 3). Noticeably, VviEXP6 transcriptsshoweda2-foldincreaseunder−Sstarvationandthe absenceof this mineral in the growingmedium repressed the transcriptionofthreeotherEXPAfamilymembers(VviEXPA5, Vvi-EXPA19andVviEXPA20).
Outofthe10XTHmembersexpressingincallustissue, two (VviXTH31and VviXTH32)werepredictedby sequence analyzes ascandidatestohavehydrolaseactivity(Fig.S7).Thequantified gene expressionof VviXTH32 wassignificantly compromised in responsetoallstressconditions(Fig.3).Moreover,VviXTH31was alsostronglyrepressedundernitrogendeficiency(TableS3).The remainingXTHsweredifferentlyregulatedaccordingtothespecific experimentalcondition.UndernitrogendeficiencyonlyVviXTH14 was differently expressed, showing a 3. fold down-regulation. Under–P,whichwastheconditionthataffectedmoreXTHs,this memberwasalsorepressed,togetherwithVviXTH2andVviXTH15 whileVviXTH4showedaclearupregulation.Onthecontrary,under –SconditionsnosignificantXTHdown-regulationwasdetected, withtwogenes(VviXTH4andVviXTH8)up-regulated(TableS3).
MorePMEgenesweredown-regulatedundermineralstarvation thanup-regulated.Thelattersituationwasobservedforthesame twomembers,VviPME1.4andVviPME1.1,inboth−Pand,toahigher extent,−Sconditions.About1/3ofthePMEgenesquantifiedwere
down-regulatedineachexperimentalcondition.Somedisplayed thesame pattern in response tomore thanone stress, namely VviPME1.19and VviPME2.14under −P and −S,and VviPME2.20 under−Nand−P.VviPME1.1wasdown-regulatedinresponseto allstresses.HighlightedistheresponseofVviPME1.4whichwas severelyimpairedunder nitrogen(5-fold downregulation)and strongly induced under sulfur starvation(6-fold up-regulation) (Fig.3).Interestingly,undermineraldepletion,PMEIgene expres-sionshowed tobe generallyup-regulated, althougha different memberwasaffectedaccordingtoeachindividualmineralstress under−Nand −Sconditionsandphosphorusstarvation signifi-cantlyimpactedthreeoutofthefourPMEIsexpressinginV.vinifera callustissues.CollectivelyPMEdown-regulationresultssuggesta reductioninenzymaticde-esterificationpotentialunderimposed mineralstress.
6.3. Looseningactivityfromcallusextracts
Theoccurrenceofdifferentamountsandrelativeproportionsof theproteinmixturethatactsontheCWtoalteritsstructural prop-ertiescanbeaddressedbymeasuringthechangesinextensionthat theyabletoinduce.Saltextractsfromthefourexperimental sam-pleswereaddedtocucumberhypocotyls,usedasmodeldicotCW specimens,inanextensometerassayandasignificantincreasein thetotaldeformationwasobservedwhenthe−Nand–Pextracts wereused(Fig.4).Theeffectwasmore evidentinextracts iso-latedfrom−Ncalluseventhoughthetotalquantityofextractable proteinshadbeenlowerthanintheotherconditions(Fig.4.Inset KClextracts).Thehighertotaldeformationobservedisthedirect resultofanincreaseoftheplasticdeformationsincetheelastic deformationwasnotsignificantlyaffectedbyanyofthemineral stresses.Endoglucanaseactivitywasestimatedthroughaviscosity testwherethehigherthedecreaseinCMCsubstrateviscosityafter incubationwithactingenzymesolutions,thehighertheenzymatic activity.Aftertwohoursincubation,theextractspreparedfrom−N callusshowedsignificantlyloweractivitythanalltheother treat-ments,whileinthoseobtainedfrom−Sand−Phigheractivities weremeasuredascomparedtothecontrol(Fig.5).
7. Discussion
Takingadvantageoftheoptimizedexperimentalcallusmodel system,insightsintotheregulationunderlyingtheeffectsof lim-itingnutrientsupplytocelldevelopmentthroughCWdynamics weregained.ApreviousworkbasedonFT-IRspectroscopyand
bio-Fig.3.Differentiallyexpressedgenestranscribedincallusundermineralstress
withrespecttocallusgrownundercompletemedium.Hierarchicalclusteringwas
performedon50CW-modifying-encodinggenesfromcandidatefamiliesshowing
expressionincallustissues.Genedendrogram(left)andconditiondendrogram(top)
wereobtainedusingPearson’suncentereddistancemetriccalculatedfromalllog2
transcriptionratios(mineralstress/control).Colorscalefromgreentoredindicates
log2transcriptionratiosfrom6-foldundertranscriptionto6-foldover
transcrip-tion).Theexactvalueofrelativeexpressionisgivenwhenastrikingfoldchangeof
4wasobserved,althoughinthispaperwediscussdifferencesingeneexpression
whenthefoldchangeatleastdoubles.Eachgeneisidentifiedbythecodeprovided
inSupplementarymaterial1.
chemicalquantificationofCWcomponentsreportschangesinthe amountorrearrangementsofcelluloseandmatrixlinkedglycans, inthelevelsofpectinmethyl-esterificationandinthestrengththe polysaccharidesassociateintotheCWasthemaineffectsinduced byN,PandSmineraldeprivation(Fernandesetal.,2013).
Confirming biochemical changes observed (Fernandes et al., 2013),undermineralstressareductionincelluloseandanincrease inpectincontentswereperceivedviaCalcofluorandtoluidineblue labelling,respectively.Similarly,higherlabellingbytheantibody
Fig.4. Plastic(dP),Elastic(dE)andTotal(dT)deformationofcucumberhypocotyls
whensaltextractsfromcallusgrownundernitrogen(−N),phosphorus(−P),
sul-fur(−S)depletionandcontrol(C)wereapplied.Innertablerepresentstheprotein
quantificationforthesaltextractsfrom−N,−P,−Sandcontrol±SDof6
measure-ments.Thesameamountofsolubleprotein,ineachtreatment,wasusedinalltests.
Differentlettersindicatesignificantdifferencesatp<0.05.
Fig.5.-1,4-Endo-glucanaseactivityofsaltextractsfromcallusgrownunder
nitro-gen(−N),phosphorus(−P),sulfur(−S)depletionandcontrol(C).Activityisgivenas
thedecreaseinviscosity(%)withrespecttotimezero.Thesameamountofsoluble
protein,ineachtreatment,wasusedinalltests.Differentlettersindicatesignificant
differencesatp<0.05,n=9.
identifyingdimericassociationsofpecticchainsthroughcalcium ions,2F4,wasdetectedin–Ncallus,supportingtheevidenceof alowerdegreeofmethyl-esterification,andthepromotionofthe conditionsfavorabletotheformationofcalciumbridges(Pelloux etal.,2007).
CW-biosynthesisandmodificationassociatedgenesarepresent in large multigenicfamilies withrelated overlapping functions whichmayleadtocompensatorymechanismsforthetranscription changesofmostofthesegenes(Giovannoni,2004).Makinguseof thesequencedV.viniferagenomeavailability(Jaillonetal.,2007; Velascoetal.,2007)list,acomprehensiveinsilicoanalysiswas con-ductedto,inafirststep,comparethesizeofthegenefamilieswith otherplantmodelspecies.Then,thetranscriptionpatternofgenes encodingCWsynthase,hydrolase,trans-glycosylase,expansinand esteraseenzymeswhich,basedontheirknownmodesofaction andcombinedactivitymayresultintheobservedchanges,were examined.Thisapproachwascomplementedwiththeevaluationof
saltextractsloosening–promotingactivityondicotCWspecimens (Figs.4and5).
MostoftheV.viniferaCW-relatedgenefamiliesincludea simi-larnumberofmembersthanA.thaliana,O.sativaandP.trichocarpa. Moreover,thedendrogramanalysisofV.viniferaCW-relatedamino acidsequences,showedclusteringwithorthologuesfromthosein modelspecies(Figs.S3–S5),aspreviouslyobservedbyBaumann etal.(2007),suggesting aconservationofCW biosynthesis and modificationmechanismsthroughoutangiospermevolution.
Geneexpressionofkeycandidategenesabovealog2 ±2-fold
changerelativetothecontrolshowedthatresponsivemembers weredetectedinallfamilies(Fig.2andTableS3).Despitetheimpact ofnitrogenstarvation,leadingtomoredramaticdevelopmental andmorphologicalmodificationsincallustissues(Fernandesetal., 2013;Fig.S1),alowernumberofgeneswithsignificant expres-sionalteration,wasobserved.(Fig.3andTableS3).Lowerlevelsof celluloseweredetectedunder−Nand−P(Fernandesetal.,2013; Fig.2),whichleadustoinvestigatethegeneexpressionoffamilies associatedwithcellulosebiosynthesis.CesAarepresentin multi-genicfamilieswithatleast10membersinA.thaliana,10inO.sativa (RichmondandSomerville,2000),andatleast18inP.trichocarpa (Suzukietal.,2006).ExceptforVviCesA6under−Sconditions,all othersignificantlyaffectedgenesshowedanincreased(ca.2–3log2
fold-change)transcriptaccumulation,notexplainingthereduction intheobservedcellulosecontent.InArabidopsis,threedistinctCesA proteinsarerequiredtoproducecellulose(Desprezetal.,2007). IfVviCesA6isthecounterpartofAtCesA6,itcanbeassumedthat thecallusprimaryCWinourexperimentalsystemmayhavebeen affectedinsimilarwaytotheirregularxylem(irx)mutant lines whichharborlesionsinAtCesAs4,7,and8(Tayloretal.,2003). Acceptingthehypothesisofnon-redundancy,inthelackofoneof theproteinstheassemblageofthecomplexisimpairedwithout for-mationofthecellulosemicrofiber(Desprezetal.,2007).Strikingly, VviCesAdown-regulationwasobservedonlyunder–Sconditions, whichistheonlytestedmineralthatdoesnotimpactareduction incellulosecontent(Fernandesetal.,2013).
Nevertheless,CesAactivityisnotsufficienttoproducecellulose, requiringthecombined actionwithmembers fromother fami-lies.Amongthose,thesub-classesAandC oftheGH9family is alsoknowntointeractincellulosebiosynthesis.Regardingclass A,amutant(KORRIGAN)impairedinthisgeneexpressionshowed a dwarf phenotypeand changes in thecellulose-XyG network, demonstratingthatthesegenemembersareessentialfora cor-rectcelluloseformation(Nicoletal.,1998).V.viniferacallustissue growingundermineralstressdidnotshowsignificant modifica-tionsintheexpressionofthesegenemembers.Ontheotherhand, classCGH9harborsacellulosebindingmodule(CBM)attachedto theC-terminusofthecatalyticdomain(Urbanowiczetal.,2007b), anditsroleincellulosebiochemistrywasrecentlydemonstratedin P.trichocarpa.Inthisspecies,aspecificmember,PtGH9C2,showed tobeinvolved inregulatingthedegreeofcellulose crystallinity (Glassetal.,2015).AsproposedbyFujitaetal.(2011)thisproperty regulatestherateofexpansionoftheprimaryCWbyrestricting thenumberofcross-linkswithhemicelluloses(Lai-Kee-Himetal., 2002).PtGH9C2mayplayaroleincessationofprimarygrowth, therebyresultinginimpairedorenhancedgrowthofpoplarlines overexpressingorRNAisuppressed,respectively(Glassetal.,2015). UndermineralstresstheonlyGH9Cthatexpressedincallustissues, VviGH9C2,wasseverelydown-regulatedunder−N and, surpris-ingly,under–Sconditions,showinganinvariantexpressionpattern under–P(Figs.1and3andTableS3).Theobservedreductionin endoglucanaseactivityunder−N(Fig.5)couldcausetheinhibition ofmicrofibril crystallization and consequent increase cellulose-XyGcross-linkingtoreinforcethewall(Fujitaetal.,2011).
Under–Pand–SspecificXTHandPMEfamilymemberswere up-regulated,whileotherswererepressed.Thisobservationcan
berelated totheopposite effects in CW modifications that, as discussed,particularmembersofbothfamiliescanexert(Osato et al.,2006).Regarding XTHs,the enzymescoded by this gene familycanholddistinctactivities,xyloglucanendotransglucosylase (XET),xyloglucanendohydrolase(XEH)orboth,oftentoproduce paradoxaleffectsontheCW(EklöfandBrumer,2010).Hencethe assignmentofeachV.viniferaXTHtoaputativeactivitywas con-ductedbasedonsequenceanalyzes(EklöfandBrumer,2010).As expected,andinaccordancewithJohanssonetal.(2004)in Pop-ulus,keyactive-sitesrevealedsubtledifferencesrestrictedtotwo loopsoutsidethesubstrate-bindingcleft,attributedtotwo inser-tionsinXTHenzymesproposedtodisplayXEHactivity(Eklöfand Brumer,2010).TwoV. viniferaXTHproteinsdisplayedan inser-tionofthosemotifs,makingthemstrongcandidatesasXEHs(Fig. S7).ThenumberofV.viniferaofXTH-XEHmembersissimilarto theoneintheA.thalianagenome(Baumannetal.,2007)and,in thepresentstudy,thesegeneswererepressedunderallmineral stresses,oftenathighlevels.RecentstudiesreportedbyKaewthai etal.(2013)demonstratethattheseenzymeshavenosignificant effectongrowthpatterns ordevelopmentalphenotypes, which maysuggesttheiractionaskeyenzymesinaXyG-recycling path-waywhereanexcessofnon-reducingendsleadstoareinforced XyGnetwork(Sampedroetal.,2010,2012).Ontheotherhand, XTHgenesmayfunctionredundantly(Matsuietal.,2005),withthe repressionofonemembercompensatedbytheup-transcriptionof others.
PMEgenesalsobelongtoamultigene family(Markovicand Janecek,2004).Somememberscarry anN-terminal PROregion extension,whichprecedesaconserveddomainsimilartothePMEI domain(Jolie etal., 2010).Depending on theabsence or pres-enceofthisPROregion,PMEsareclassifiedintotwosubfamilies: type II/group1and typeI/group2 respectively(Micheli,2001). After the integration into the CW, PMEs can randomly or lin-earlyde-esterifytheHGchain(MarkovicandKohn,1984).Random PMEde-esterificationactivatesthepolygalacturonaseactivity pro-motingtheCWlooseningwhilelinearPMEde-esterificationcan promoteCa2+-linkedgelstructuresand stiffentheCW (Micheli, 2001).It is referred that plantPMEs withan acidicpI act in a nonblock-wisefashion,while plantbasicpI PMEs,which repre-sentsmostisoforms,actinablock-wisefashion(BoschandHepler, 2005)makingthesefamiliesstrongcandidatestoactin compen-satorymechanismswithinthesamefunction.Hence,thelower globaldegree(Fernandesetal.,2013)andpattern(Fig.1)of methyl-esterificationobservedundersomemineralstarvationconditions cannotbedirectlyexplainedbythePMEgeneexpressionlevels.In factmostPMEgenesweredown-regulatedandallPMEIgeneswere up-regulatedwiththeexceptionofthebasicPME1.4andPME1.11 under−Pand−S.AnequivalentbalancebetweenPMEandPMEI controllingtherateofde-esterification,wasobservedinArabidopsis roots(Wilsonetal.,2015).Fromthesefindingswehypothesizethat undermineralstressesthebasicPMEsproducelonglinearstretches ofunesterifiedHGchainspromotingtheformationofCa2+-linked
gelstructuresand,inthisway,stiffeningtheCW.Asawhole,the resultsofgeneexpressionchangesinresponsetotheindividual mineralstressesareinaccordancewithpreviousevidencesthat theresponseandeventualadaptationarespecifictoeachstress.
Afterincubationofproteinsaltextractswithheatinactivated cucumberhypocotylusedasdicotCWspecimensunderconditions thatpromoteextensibility,increasesintheplasticdeformations were observed under –N and −P callus (Fig. 4).Plastic defor-mation,meaninganirreversibleincreaseinlengthafterremoval of an appliedstretching force, is a necessary conditionfor the wall-looseningreactionsinvolvedingrowth(HohlandSchopfer, 1992).ExpansinsandXTHsareCW-looseningagentsthatregulate CWexpansionandcellenlargementthroughelasticdeformation (Cosgrove,2000;Miedesetal.,2013).Thegeneraldown-regulation
of␣-expansinand mostXTHs genesinV. viniferacallustissues observedinresponsetomineralstressareinlinewiththeresults obtainedinextensibilitytests,wherenoalterationintheelastic componentofthedeformationswasobserved.
Consideringthegeneexpressionresultsdiscussedabove,itmay bespeculatedthat thelower proportion ofhydrolyticenzymes foundintheproteinextractsundermineralstressconditionshad lesseffectonthecucumberhypocotylCWspolysaccharides.This feature maypromote irreversiblemodifications in the physical propertiesduetomechanical,non-enzymaticeffects.Infact, XTH-XEH,GH9CandPMEexpressingincalluswereamongthegeneswith amoredramaticdown-regulation,alongwiththereducedactivity ofendoglucanaseunder−N,suggestingthattheputativeencoding enzymesarepresentatlowerlevelsintheextractsappliedtothe inactivateddicotCWsamples.
Theuseof ssNMRCW analyzes unraveled that less than8% ofcellulosesurfaceisincontactwithXyG(Boottenetal.,2004; Dick-Perezetal.,2011),withpectinsfillingthegaps.Pectinsare presentedasverydynamicpolymerswhichduetotheirhydrophilic charactermayeasemicrofibrilsmotionsasCWexpands,reducing thedirectcellulose–cellulosecontacts(ParkandCosgrove,2015). InsteadofXyG,pecticmonosaccharides(mostlikelyfromRG-Iside chainsgalactanandarabinanrich(Zykwinskaetal.,2007,2008) maybeassociatedtothecellulose(Cosgrove,2014).Pectinscan thenserveasmechanicaltethersbetweenmicrofibrils(Wangetal., 2012;Peaucelleetal.,2012).Usingthesamesystemwehad pre-viouslyobserved anincrease in arabinoseunder−N conditions leading toCW reinforcement althoughstill allowing significant plasticdeformation(Fig.4).Theseresultsagreewiththepresenceof “biomechanicalhotspots”asproposedbyParkandCosgrove(2012, 2015) inwhich wallextensibility is less dependentonthe vis-coelasticityofthematrixpolymersdependingmoreoftheselective separationbetweenmicrofibrilsatlimitedCWsites.
TheroleofhydrolyticenzymesinCWlooseningwasformerly envisionedastheprimeplayersintheexpansionprocess(Farkas andMaclachlan,1988;McDougallandFry,1990).Althoughitis notclearlyacknowledgedthattheybreakglycosidicbondsof crys-talline cellulose (Vissenberg et al., 2001; Cosgrove, 2005), it is recognizedthattheiractivitycouldcontributetothelooseningof theCW,makingitmorepliableforexpansion(Cosgrove,2005).Park and Cosgrove (2012)reported that -1,4-endo-glucanasesmay induceplasticdeformation.Thisassumptionagreeswithour obser-vationsontheincreaseinendoglucanaseactivityandtheincrease inplasticdeformationunder−P.
Theresultstakenasawholesupportthehypothesisthat differ-entmineralstressesimpactdifferentresponsesintheCW-related mechanismsthatunderliedevelopment,withnitrogeneffecting thoseresponsesmoredramaticallyandsulfurleadingtoless pro-nouncedresponses.Thismaybeduetothevitalroleofnitrogen inplantmetabolism.Infact,askeyelementinproteinsynthesis, nitrogendepletioncanredirectthemetabolismpreventingprotein compensationbyothermembersofthesamefamily.
Acknowledgments
The research was funded by Fundac¸ão para a Ciência e a Tecnologia (FCT) project PTDC/AGR-GPL/099624/2008, CBAA (PestOE/AGR/UI0240/2011)andGrantSFRH/BD/64047/2009toJCF.
References
Arnold,K.,Bordoli,L.,Kopp,J.,Schwede,T.,2006.TheSWISS-MODELworkspace:a
web-basedenvironmentforproteinstructurehomologymodelling.
Bioinformatics22,195–201,http://dx.doi.org/10.1093/bioinformatics/bti770.
Baumann,M.J.,Eklof,J.M.,Michel,G.,Kallas,A.M.,Teeri,T.T.,Czjzek,M.,BrumerIII,
H.,2007.Structuralevidencefortheevolutionofxyloglucanaseactivityfrom
xyloglucanendo-transglycosylases:biologicalimplicationsforcellwall
metabolism.PlantCell19,1947–1963,http://dx.doi.org/10.1105/tpc.107.
Bellincampi,D.,Camardella,L.,Delcour,J.A.,Desseaux,V.,D’Ovidio,R.,Durand,A.,
Elliot,G.,Gebruers,K.,Giovane,A.,Juge,N.,Sorensen,J.F.,Svensson,B.,Vairo,D.,
2004.Potentialphysiologicalroleofplantglycosidaseinhibitors.BBAProteins
Proteom.1696,265–274,http://dx.doi.org/10.1016/j.bbapap.2003.10.011.
Bootten,T.J.,Harris,P.J.,Melton,L.D.,Newman,R.H.,2004.Solid-state13CNMR
spectroscopyshowsthatthexyloglucansintheprimarycellwallsofmung
bean(VignaradiataL.)occurindifferentdomains:anewmodelfor
xyloglucan-celluloseinteractionsinthecellwall.J.Exp.Bot.55,571–583,
http://dx.doi.org/10.1093/jxb/erh065.
Bosch,M.,Hepler,P.K.,2005.Pectinmethylesterasesandpectindynamicsinpollen
tubes.PlantCell17,3219–3226,http://dx.doi.org/10.1105/tpc.105.037473.
Bradford,M.M.,1976.Arapidandsensitivemethodforthequantitationof
microgramquantitiesofproteinutilizingtheprincipleofprotein-dyebinding. Anal.Biochem.72,248–254.
Braidwood,L.,Breuer,C.,Sugimoto,K.,2014.Mybodyisacage:mechanismsand
modulationofplantcellgrowth.NewPhytol.201,388–402,http://dx.doi.org/
10.1111/nph.12473.
Brummell,D.A.,Harpster,M.H.,2001.Cellwallmetabolisminfruitsofteningand
qualityanditsmanipulationintransgenicplants.PlantMol.Biol.47,311–340,
http://dx.doi.org/10.1023/A.1010656104304.
delCampillo,E.,Gaddam,S.,Mettle-Amuah,D.,Heneks,J.,2012.Ataleoftwo
tissues:AtGH9C1isanendo--1,4-glucanaseinvolvedinroothairand
endospermdevelopmentinArabidopsis.PLoSOne7,e49363,http://dx.doi.org/
10.1371/journal.pone.0049363.
Carpita,N.,Tierney,M.,Campbell,M.,2001.Molecularbiologyoftheplantcell
wall:searchingforthegenesthatdefinestructure,architectureanddynamics.
PlantMol.Biol.47,1–5,http://dx.doi.org/10.1023/A.1010603527077.
Chevenet,F.,Brun,C.,Banuls,A.L.,Jacq,B.,Chisten,R.,2006.TreeDyn:towards
dynamicgraphicsandannotationsforanalysesoftrees.BMCBioinf.7,439,
http://dx.doi.org/10.1186/1471-2105-7-439.
Choi,D.,Cho,H.T.,Lee,Y.,2006.Expansinsexpandingimportanceinplantgrowth
anddevelopment.Physiol.Plant.126,511–518,http://dx.doi.org/10.1111/j.
1399-3054.2006.00612.x.
Coito,J.L.,Rocheta,M.,Carvalho,L.,Amâncio,S.,2012.Microarray-based
uncoveringreferencegenesforquantitativerealtimePCRingrapevineunder
abioticstress.BMCRes.Notes5,220,
http://dx.doi.org/10.1186/1756-0500-5-220.
Cosgrove,D.J.,1993.Howdoplantcellwallsextend?PlantPhysiol.102,1–6.
Cosgrove,D.J.,1999.Enzymesandotheragentsthatenhancecellwallextensibility.
Annu.Rev.PlantPhysiol.PlantMol.Biol.(50),391–417,http://dx.doi.org/10.
1146/annurev.arplant.50.1.391.
Cosgrove,D.J.,2000.Looseningofplantcellwallsbyexpansins.Nature407,
321–326,http://dx.doi.org/10.1038/35030000.
Cosgrove,D.J.,2005.Growthoftheplantcellwall.Nat.Rev.Mol.CellBiol.6,
850–861.
Cosgrove,D.J.,Jarvis,M.C.,2012.Comparativestructureandbiomechanicsofplant
primaryandsecondarycellwalls.Front.PlantSci.3(204),http://dx.doi.org/10.
3389/fpls.2012.00204.
Cosgrove,D.J.,2014.Re-constructingourmodelsofcelluloseandprimarycellwall
assembly.Curr.Opin.PlantBiol.22,122–131,http://dx.doi.org/10.1016/j.pbi.
2014.11.001.
Derbyshire,P.,McCann,M.C.,Roberts,K.,2007.Restrictedcellelongationin
Arabidopsishypocotylsisassociatedwithareducedaveragepectin
esterificationlevel.BMCPlantBiol.7,31,
http://dx.doi.org/10.1186/1471-2229-7-31.
Desprez,T.,Juraniec,M.,Crowell,E.F.,Jouy,H.,Pochylova,Z.,Parcy,F.,Höfte,H.,
Gonneau,M.,Vernhettes,S.,2007.Organizationofcellulosesynthase
complexesinvolvedinprimarycellwallsynthesisinArabidopsisthaliana.Proc.
Natl.Acad.Sci.U.S.A.104,15572–15577,http://dx.doi.org/10.1073/pnas.
0706569104.
DiMatteo,A.,Giovane,A.,Raiola,A.,Camardella,L.,Bonivento,D.,DeLorenzo,G.,
Cervone,F.,Bellincampi,D.,Tsernoglou,D.,2005.Structuralbasisforthe
interactionbetweenpectinmethylesteraseandaspecificinhibitorprotein.
PlantCell17,849–858,http://dx.doi.org/10.1105/tpc.104.028886.
Dick-Perez,M.,Zhang,Y.,Hayes,J.,Salazar,A.,Zabotina,O.A.,Hong,M.,2011.
Structureandinteractionsofplantcell-wallpolysaccharidesbytwo-and
three-dimensionalmagicangle-spinningsolid-stateNMR.Biochemistry50,
989–1000,http://dx.doi.org/10.1021/bi101795q.
Doblin,M.S.,Pettolino,F.,Bacic,A.,2010.Plantcellwalls:theskeletonoftheplant
world.Funct.PlantBiol.37,357–381http://dx.doi.org/10.1071/FP09279.
Durbin,M.L.,Lewis,L.N.,1988.CellulasesinPhaseolusvulgaris.MethodsEnzymol.
160,342–351,http://dx.doi.org/10.1016/0076-6879(88)60137-6.
Edgar,R.,2004a.MUSCLE:amultiplesequencealignmentmethodwithreduced
timeandspacecomplexity.BMCBioinf.5,113,http://dx.doi.org/10.1186/
1471-2105-5-113.
Edgar,R.C.,2004b.MUSCLE:multiplesequencealignmentwithhighaccuracyand
highthroughput.NucleicAcidsRes.32,1792–1797,http://dx.doi.org/10.1093/
nar/gkh340.
Eklöf,J.M.,Brumer,H.,2010.TheXTH:genefamily:anupdateonenzyme
structure,function,andphylogenyinxyloglucanremodeling.PlantPhysiol.
153,456–466,http://dx.doi.org/10.1104/pp.110.156844.
Endler,A.,Persson,S.,2011.CellulosesynthasesandsynthesisinArabidopsis.Mol.
Farkas,V.,Maclachlan,G.,1988.Stimulationofpea1,4--glucanaseactivityby oligosaccharidesderivedfromxyloglucan.Carbohydr.Res.184,213–219.
Farrokhi,N.,Burton,R.A.,Brownfield,L.,Hrmova,M.,Wilson,S.M.,Bacic,A.,
Fincher,G.B.,2006.Plantcellwallbiosynthesis:genetic,biochemicaland
functionalgenomicsapproachestotheidentificationofkeygenes.Plant
Biotechnol.J.4,145–167,http://dx.doi.org/10.1111/j.1467-7652.2005.00169.x.
Fernandes,J.C.,García-Angulo,P.,Goulao,L.F.,Acebes,J.L.,Amâncio,S.,2013.
Mineralstressaffectsthecellwallcompositionofgrapevine(VitisviniferaL.)
callus.PlantSci.205–206,111–120,http://dx.doi.org/10.1016/j.plantsci.2013.
01.013.
Fujita,M.,Himmelspach,R.,Hocart,C.H.,Williamson,R.E.,Mansfield,S.D.,
Wasteneys,G.O.,2011.Corticalmicrotubulesoptimizecell-wallcrystallinityto
driveunidirectionalgrowthinArabidopsis.PlantJ.66,915–928,http://dx.doi.
org/10.1111/j.1365-313X.2011.04552.x.
Giovannoni,J.J.,2004.Geneticregulationoffruitdevelopmentandripening.Plant
Cell16(Suppl),S170–S180,http://dx.doi.org/10.1105/tpc.019158.
Glass,M.,Barkwill,S.,Unda,F.,Mansfield,S.D.,2015.Endo--1,4-glucanases
impactplantcellwalldevelopmentbyinfluencingcellulosecrystallization.J.
Integr.PlantBiol.57,396–410,http://dx.doi.org/10.1111/jipb.12353.
Goulao,L.F.,2010.Pectinde-esterificationandfruitsoftening:revisitingaclassical
hypothesis.StewartPostharvestRev.1,1–12,http://dx.doi.org/10.2212/spr.
2010.1.7.
Guex,N.,Peitsch,M.C.,1997.SWISS-MODELandtheSwiss-Pdbviewer:an
environmentforcomparativeproteinmodeling.Electrophoresis18,
2714–2723,http://dx.doi.org/10.1002/elps.1150181505.
Guindon,S.,Dufayard,J.-F.,Lefort,V.,Anisimova,M.,Hordijk,W.,etal.,2010.New
algorithmsandmethodstoestimatemaximum-likelihoodphylogenies:
assessingtheperformanceofPhyML3.0.Syst.Biol.59,307–321,http://dx.doi.
org/10.1093/sysbio/syq010.
Handakumbura,P.P.,Matos,D.A.,Osmont,K.S.,Harrington,M.J.,Heo,K.,Kafle,K.,
Kim,S.H.,Baskin,T.I.,Hazen,S.P.,2013.PerturbationofBrachypodium
distachyonCELLULOSESYNTHASEA4or7resultsinabnormalcellwalls.BMC
PlantBiol.13,131,http://dx.doi.org/10.1186/1471-2229-13-131.
Hohl,M.,Schopfer,P.,1992.Physicalextensibilityofmaizecoleoptilecellwalls:
apparentplasticextensibilityisduetoelastichysteresis.Planta187,498–504,
http://dx.doi.org/10.1007/BF00199968.
Hongo,S.,Sato,K.,Yokoyama,R.,Nishitani,K.,2012.Demethylesterificationofthe
primarywallbyPECTINMETHYLESTERASE35providesmechanicalsupportto
theArabidopsisstem.PlantCell24,2624–2634,http://dx.doi.org/10.1105/tpc.
112.099325.
Jackson,P.,Galinha,C.,Pereira,C.,Fortunato,A.,Soares,N.,Amâncio,S.,Pinto,C.,
2001.Ricardorapiddepositionofextensinduringtheelicitationofgrapevine
callusculturesisspecificallycatalysedbya40kDaperoxidase.PlantPhysiol.
127,1065–1076http://dx.doi.org/10.1104/pp.01019.
Jaillon,O.,Aury,J.M.,Noel,B.,Policriti,A.,Clepet,C.,Casagrande,A.,Choisne,N.,
Aubourg,S.,Vitulo,N.,Jubin,C.,etal.,2007.Thegrapevinegenomesequence
suggestsancestralhexaploidizationinmajorangiospermphyla.Nature449,
463–467,http://dx.doi.org/10.1038/nature06148.
Johansson,P.,Brumer3rd,H.,Baumann,M.J.,Kallas,A.M.,Henriksson,H.,Denman,
S.E.,Teeri,T.T.,Jones,T.A.,2004.Crystalstructuresofapoplarxyloglucan
endotransglycosylaserevealdetailsoftransglycosylationacceptorbinding.
PlantCell16,874–886,http://dx.doi.org/10.1105/tpc.020065.
Jolie,R.P.,Duvetter,T.,VanLoey,A.M.,Hendrickx,M.E.,2010.Pectin
methylesteraseanditsproteinaceousinhibitor:areview.Carbohydr.Res.345,
2583–2595,http://dx.doi.org/10.1016/j.carres.2010.10.002.
Juge,N.,2006.Plantproteininhibitorsofcellwalldegradingenzymes.TrendsPlant
Sci.11,359–367,http://dx.doi.org/10.1016/j.tplants.2006.05.006.
Kaewthai,N.,Gendre,D.,Eklöf,J.M.,Ibatullin,F.M.,Ezcurra,I.,Bhalerao,R.P.,
Brumer,H.,2013.GroupIII-AXTH:genesofArabidopsisencodepredominant
xyloglucanendohydrolasesthataredispensablefornormalgrowth.Plant
Physiol.161,440–454,http://dx.doi.org/10.1104/pp.112.207308.
Lai-Kee-Him,J.,Chanzy,H.,Muller,M.,Putaux,J.,Imai,T.,Bulone,V.,2002.Invitro
versusinvivocellulosemicrofibrilsfromplantprimarywallsynthases:
structuraldifferences.J.Biol.Chem.277,36931–36939,http://dx.doi.org/10.
1074/jbc.M203530200.
Landrein,B.,Hamant,O.,2013.Howmechanicalstresscontrolsmicrotubule
behaviorandmorphogenesisinplants:history,experimentsandrevisited
theories.PlantJ.75,324–338,http://dx.doi.org/10.1111/tpj.12188.
Lerouxel,O.,Cavalier,D.M.,Liepman,A.H.,Keegstra,K.,2006.Biosynthesisofplant
cellwallpolysaccharides—acomplexprocess.Curr.Opin.PlantBiol.9,
621–630,http://dx.doi.org/10.1016/j.pbi.2006.09.009.
Liners,F.,Letesson,J.J.,Didembourg,C.,VanCutsem,P.,1989.Monoclonal
antibodiesagainstpectin:recognitionofaconformationinducedbycalcium.
PlantPhysiol.91,1419–1424http://dx.doi.org/10.1104/pp.91.4.1419.
Malinovsky,F.G.,Fangel,J.U.,Willats,W.G.T.,2014.Theroleofthecellwallinplant
immunity.Front.PlantSci.5(178),http://dx.doi.org/10.3389/fpls.2014.00178.
Marcus,S.E.,Verhertbruggen,Y.,Hervé,C.,Ordaz-Ortiz,J.J.,Farkas,V.,Pedersen,
H.L.,Willats,W.G.T.,Knox,J.P.,2008.Pectichomogalacturonanmasks
abundantsetsofxyloglucanepitopesinplantcellwalls.BMCPlantBiol.8,60,
http://dx.doi.org/10.1186/1471-2229-8-60.
Markovic,O.,Janecek,S.,2004.Pectinmethylesterases:sequence-structural
featuresandphylogeneticrelationships.Carbohydr.Res.339,2281–2295,
http://dx.doi.org/10.1016/j.carres.2004.06.023.
Markovic,O.,Kohn,R.,1984.ModeofpectindeesterificationinTrichodremareesei
pectinesterese.Experientia5,842–843.
Matsui,A.,Yokoyama,R.,Seki,M.,Ito,T.,Shinozaki,K.,Takahashi,T.,Komeda,Y.,
Nishitani,K.,2005.AtXTH27playsanessentialroleincellwallmodification
duringthedevelopmentoftrachearyelements.PlantJ.42,525–534,http://dx.
doi.org/10.1111/j.1365-313X.2005.02395.x.
McDougall,G.J.,Fry,S.C.,1990.Xyloglucanoligosaccharidespromotegrowthand
activatecellulase.Evidenceforaroleofcellulaseincellexpansion.Plant
Physiol.93,1042–1048http://dx.doi.org/10.1104/pp.93.3.1042.
McQueen-Mason,S.,Durachko,D.M.,Cosgrove,D.J.,1992.Twoendogenous
proteinsthatinducecellwallextensioninplants.PlantCell4,1425–1433
http://dx.doi.org/10.1105/tpc.4.11.1425.
McQueen-Mason,S.J.,Cosgrove,D.J.,1995.Expansinmodeofactiononcellwalls
analysisofwallhydrolysis,stressrelaxationandbinding.PlantPhysiol.107,
87–100http://dx.doi.org/10.1104/pp.107.1.87.
Micheli,F.,2001.Pectinmethylesterases:cellwallenzymeswithimportantroles
inplantphysiology.TrendsPlantSci.6,414–419,http://dx.doi.org/10.1016/
s1360-1385(01)02045-3.
Miedes,E.,Herbers,K.,Sonnewald,U.,Lorences,E.P.,2010.Overexpressionofacell
wallenzymereducesxyloglucandepolymerizationandsofteningoftransgenic
tomatofruits.J.Agric.FoodChem.58,5708–5713,http://dx.doi.org/10.1021/
jf100242z.
Miedes,E.,Suslov,D.,Vandenbussche,F.,Kenobi,K.,Ivakov,A.,VanDerStraeten,
D.,etal.,2013.Xyloglucanendotransglucosylase/hydrolase(XTH)
overexpressionaffectsgrowthandcellwallmechanicsinetiolatedArabidopsis hypocotyls.J.Exp.Bot.64,2481–2497.
Murashige,T.,Skoog,F.,1962.Arevisedmediumforrapidgrowthandbioassays
withtobaccotissue.Physiol.Plant.15,493–497,http://dx.doi.org/10.1111/j.
1399-3054.1962.tb08052.x.
Nicol,F.,His,I.,Jauneau,A.,Vernhettes,S.,Canut,H.,Höfte,H.,1998.Aplasma
membrane-boundputativeendo-1,4-beta-d-glucanaseisrequiredfornormal
wallassemblyandcellelongationinArabidopsis.EMBOJ.17,5563–5576,
http://dx.doi.org/10.1093/emboj/17.19.5563.
Oliveros,J.C.,2007.VENNY:aninteractivetoolforcomparinglistswithVenn
Diagrams,http://bioinfogp.cnb.csic.es/tools/venny/index.html.
Osato,Y.,Yokoyama,R.,Nishitani,K.,2006.AprincipalroleforAtXTH18in
Arabidopsisthalianarootgrowth—afunctionalanalysisusingRNAiplants.J.
PlantRes.119,153–162,http://dx.doi.org/10.1007/s10265-006-0262-6.
Park,Y.B.,Cosgrove,D.J.,2012.Arevisedarchitectureofprimarycellwallsbased
onbiomechanicalchangesinducedbysubstrate-specificendoglucanases.Plant
Physiol.158,1933–1943,http://dx.doi.org/10.1104/pp.111.192880.
Park,Y.B.,Cosgrove,D.J.,2015.Xyloglucananditsinteractionswithother
componentsofthegrowingcellwall.PlantCellPhysiol.56,180–194,http://dx.
doi.org/10.1093/pcp/pcu204.
Peaucelle,A.,Louvet,R.,Johansen,J.N.,Hofte,H.,Laufs,P.,Pelloux,J.,Mouille,G.,
2008.Arabidopsisphyllotaxisiscontrolledbythemethyl-esterificationstatus
ofcell-wallpectins.Curr.Biol.18,1943–1948,http://dx.doi.org/10.1016/j.cub.
2008.10.065.
Peaucelle,A.,Braybrook,S.A.,LeGuillou,L.,Bron,E.,Kuhlemeier,C.,Höfte,H.,2011.
Pectin-inducedchangesincellwallmechanicsunderlieorganinitiationin
Arabidopsis.Curr.Biol.21,1720–1726,http://dx.doi.org/10.1016/j.cub.2011.08.
057.
Peaucelle,A.,Braybrook,S.,Hofte,H.,2012.Cellwallmechanicsandgrowth
controlinplants:theroleofpectinsrevisited.Front.PlantSci.3,121,http://dx.
doi.org/10.3389/fpls.2012.00121.
Pelloux,J.,Rustérucci,C.,Mellerowicz,E.J.,2007.Newinsightsintopectin
methylesterasestructureandfunction.TrendsPlantSci.12,267–277,http://
dx.doi.org/10.1016/j.tplants.2007.04.001.
Petersen,T.N.,Brunak,S.,vonHeijne,G.,Nielsen,H.,2011.SignalP4.0:
discriminatingsignalpeptidesfromtransmembraneregions.Nat.Methods8,
785–786,http://dx.doi.org/10.1038/nmeth.1701.
Pilling,E.,Höfte,H.,2003.Feedbackfromthewall.Curr.Opin.PlantBiol.6,
611–616,http://dx.doi.org/10.1016/j.pbi.2003.09.004.
Popper,Z.A.,Fry,S.C.,2005.Widespreadoccurrenceofacovalentlinkagebetween
xyloglucanandacidicpolysaccharidesinsuspension-culturedangiosperm
cells.Ann.Bot.96,91–99,http://dx.doi.org/10.1093/aob/mci153.
Potters,G.,Pasternak,T.P.,Guisez,Y.,Palme,K.J.,Jansen,M.A.K.,2007.
Stress-inducedmorphogenicresponses:growingoutoftrouble?TrendsPlant
Sci.12,98–105,http://dx.doi.org/10.1016/j.tplants.2007.01.004.
Quevillon,E.,Silventoinen,V.,Pillai,S.,Harte,N.,Mulder,N.,Apweiler,R.,Lopez,R.,
2005.InterProScan.proteindomainsidentifier.NucleicAcidsRes.33,
W116–W120,http://dx.doi.org/10.1093/nar/gki442(WebServerissue).
Reid,K.E.,Olsson,N.,Schlosser,J.,Peng,F.,Lund,S.T.,2006.Anoptimizedgrapevine
RNAisolationprocedureandstatisticaldeterminationofreferencegenesfor
real-timeRT-PCRduringberrydevelopment.BMCPlantBiol.6,27,http://dx.
doi.org/10.1186/1471-2229-6-27.
Richmond,P.A.,Métraux,J.P.,Taiz,L.,1980.Cellexpansionpatternsand
directionalityofwallmechanicalpropertiesinnitella.PlantPhysiol.65,
211–217,http://dx.doi.org/10.1104/pp.65.2.211.
Richmond,T.A.,Somerville,C.R.,2000.Thecellulosesynthasesuperfamily.Plant
Physiol.124,495–498,http://dx.doi.org/10.1104/pp.124.2.495.
Saeed,A.I.,Sharov,V.,White,J.,Li,J.,Liang,W.,Bhagabati,N.,Braisted,J.,Klapa,M.,
Currier,T.,Thiagarajan,M.,Sturn,A.,Snuffin,M.,Rezantsev,A.,Popov,D.,
Ryltsov,A.,Kostukovich,E.,Borisovsky,I.,Liu,Z.,Vinsavich,A.,Trush,V.,
Quackenbush,J.,2003.TM4:afree,open-sourcesystemformicroarraydata
managementandanalysis.Biotechniques34,374–378.
Sampedro,J.,Pardo,B.,Gianzo,C.,Guitián,E.,Revilla,G.,Zarra,I.,2010.Lackof
ingrowthdefects.PlantPhysiol.154,1105–1115,http://dx.doi.org/10.1104/ pp.110.163212.
Sampedro,J.,Gianzo,C.,Iglesias,N.,Guitián,E.,Revilla,G.,Zarra,I.,2012.AtBGAL10
isthemainxyloglucan-galactosidaseinArabidopsis,anditsabsenceresults
inunusualxyloglucansubunitsandgrowthdefects.PlantPhysiol.158,
1146–1157,http://dx.doi.org/10.1104/pp.111.192195.
Sato,S.,Kato,T.,Kakegawa,K.,etal.,2001.Roleoftheputativemembrane-bound
endo-1,4-beta-glucanaseKORRIGANincellelongationandcellulosesynthesis
inArabidopsisthaliana.PlantCellPhysiol.42,251–263,http://dx.doi.org/10.
1093/pcp/pce045.
Scognamiglio,M.A.,Ciardiello,M.A.,Tamburrini,M.,Carratore,V.,Rausch,T.,
Camardella,L.,2003.Theplantinvertaseinhibitorsharesstructuralproperties
anddisulfidebridgesarrangementwiththepectinmethylesteraseinhibitor.J. ProteinChem.22,363–369.
Somerville,C.,2006.Cellulosesynthesisinhigherplants.Annu.Rev.CellDev.Biol.
22,53–78,http://dx.doi.org/10.1146/annurev.cellbio.22.022206.160206.
Suzuki,S.,Li,L.,Sun,Y.H.,Chiang,V.L.,2006.Thecellulosesynthasegene
superfamilyandbiochemicalfunctionsofxylem-specificcellulose
synthase-likegenesinPopulustrichocarpa.PlantPhysiol.142,1233–1245,
http://dx.doi.org/10.1104/pp.106.086678.
Takahashi,J.,Rudsander,U.J.,Hedenström,M.,Banasiak,A.,Harholt,J.,Amelot,N.,
Immerzeel,P.,Ryden,P.,Endo,S.,Ibatullin,F.M.,Brumer,H.,delCampillo,E.,
Master,E.R.,Scheller,H.V.,Sundberg,B.,Teeri,T.T.,Mellerowicz,E.J.,2009.
KORRIGAN1anditsaspenhomologPttCel9A1decreasecellulosecrystallinity
inArabidopsisstems.PlantCellPhysiol.50,1099–1115,http://dx.doi.org/10.
1093/pcp/pcp062.
Takeda,T.,Furuta,Y.,Awano,T.,Mizuno,K.,Mitsuishi,Y.,Hayashi,T.,2002.
Suppressionandaccelerationofcellelongationbyintegrationofxyloglucans
inpeastemsegments.Proc.Natl.Acad.Sci.U.S.A.99,9055–9060,http://dx.
doi.org/10.1073/pnas.132080299.
Talavera,G.,Castresana,J.,2007.Improvementofphylogeniesafterremoving
divergentandambiguouslyalignedblocksfromproteinsequencealignments.
Syst.Biol.56,564–577,http://dx.doi.org/10.1080/10635150701472164.
Taylor,N.G.,Howells,R.M.,Huttly,A.K.,Vickers,K.,Turner,S.R.,2003.Interactions
amongthreedistinctCesAproteinsessentialforcellulosesynthesis.Proc.Natl.
Acad.Sci.U.S.A.100,1450–1455,http://dx.doi.org/10.1073/pnas.0337628100.
Tenhaken,R.,2015.Cellwallremodelingunderabioticstress.Front.PlantSci.5,
771,http://dx.doi.org/10.3389/fpls.2014.00771.
Urbanowicz,B.R.,Bennett,A.B.,delCampillo,E.,Catalá,C.,Hayashi,T.,Henrissat,B.,
Höfte,H.,McQueen-Mason,S.J.,Patterson,S.E.,Shoseyov,O.,Teeri,T.T.,Rose,
J.K.,2007a.Structuralorganizationandastandardizednomenclatureforplant
endo-1,4-beta-glucanases(cellulases)ofglycosylhydrolasefamily9.Plant
Physiol.144,1693–1696http://dx.doi.org/10.1104/pp.107.102574.
Urbanowicz,B.R.,Catalá,C.,Irwin,D.,Wilson,D.B.,Ripoll,D.R.,Rose,J.K.C.,2007b.A
tomatoendo--1,4-glucanase,SlCel9C1,representsadistinctsubclasswitha
newfamilyofcarbohydratebindingmodules(CBM49).J.Biol.Chem.282,
12066–12074,http://dx.doi.org/10.1074/jbc.M607925200.
Vain,T.,Crowell,E.F.,Timpano,H.,Biot,E.,Desprez,T.,Mansoori,N.,Trindade,L.M.,
Pagant,S.,Robert,S.,Höfte,H.,Gonneau,M.,Vernhettes,S.,2014.Thecellulase
KORRIGAN:ispartofthecellulosesynthasecomplex.PlantPhysiol.165, 1521–1532httsp://dx.doi.org/10.1104/pp.114.241216.
VanSandt,V.S.,Suslov,D.,Verbelen,J.P.,Vissenberg,K.,2007.Xyloglucan
endotransglucosylaseactivityloosensaplantcellwall.Ann.Bot.100,
1467–1473,http://dx.doi.org/10.1093/aob/mcm248.
Velasco,R.,Zharkikh,A.,etal.,2007.Ahighqualitydraftconsensussequenceofthe
genomeofaheterozygousgrapevinevariety.PLoSOne2,e1326,http://dx.doi.
org/10.1371/journal.pone.0001326.
Vissenberg,K.,Fry,S.C.,Verbelen,J.-P.,2001.Roothairinitiationiscoupledtoa
highlylocalizedincreaseofxyloglucanendotransglycoslyaseactionin
Arabidopsisroots.PlantPhysiol.127,1125–1135,http://dx.doi.org/10.1104/pp.
010295.
Wakabayashi,K.,Soga,K.,Kamisaka,S.,Hoson,T.,2003.Modificationofcellwall
architectureofwheatcoleoptilesgrownunderhypergravityconditions.Biol. Sci.Space17,228–229.
Wang,T.,Zabotina,O.,Hong,M.,2012.Pectin-celluloseinteractionsinthe
Arabidopsisprimarycellwallfromtwo-dimensionalmagic-angle-spinning
solid-statenuclearmagneticresonance.Biochemistry51,9846–9856,http://
dx.doi.org/10.1021/bi3015532.
Wang,T.,Park,Y.B.,Caporini,M.A.,Rosay,M.,Zhong,L.,Cosgrove,D.J.,Hong,M.,
2013.Sensitivity-enhancedsolid-stateNMRdetectionofexpansin’stargetin
plantcellwalls.Proc.Natl.Acad.Sci.U.S.A.110,16444–16449,http://dx.doi.
org/10.1073/pnas.1316290110.
Whitney,S.E.C.,Gidley,M.J.,McQueen-Mason,S.J.,2000.Probingexpansinaction
usingcellulose/hemicellulosecomposites.PlantJ.22,327–334,http://dx.doi.
org/10.1046/j.1365-313x.2000.00742.x.
Willats,W.G.,Gilmartin,P.M.,Mikkelsen,J.D.,Knox,J.P.,1999.Cellwallantibodies
withoutimmunization:generationanduseofde-esterifiedhomogalacturonan
block-specificantibodiesfromanaivephagedisplaylibrary.PlantJ.18,57–65,
http://dx.doi.org/10.1046/j.1365-313X.1999.00427.x.
Willats,W.G.T.,Orfila,C.,Limberg,G.,Buchholt,H.C.,vanAlebeek,G.J.W.M.,
Voragen,A.G.J.,Marcus,S.E.,Christensen,T.M.I.E.,Mikkelsen,J.D.,Murray,B.S.,
Knox,J.P.,2001.Modulationofthedegreeandpatternofmethyl-esterification
ofpectichomogalacturonaninplantcellwalls.Implicationsforpectinmethyl
esteraseaction,matrixproperties,andcelladhesion.J.Biol.Chem.276,
19404–19413,http://dx.doi.org/10.1074/jbc.M011242200.
Wilson,M.H.,Holman,T.J.,Sorensen,I.,Cancho-Sanchez,E.,Wells,D.M.,Swarup,
R.,etal.,2015.Multi-omicsanalysisidentifiesgenesmediatingtheextension
ofcellwallsintheArabidopsisthalianarootelongationzone.Front.CellDev.
Biol.3,10,http://dx.doi.org/10.3389/fcell.2015.00010.
Wolf,S.,Mravec,J.,Greiner,S.,Mouille,G.,Höfte,H.,2012.Plantcellwall
homeostasisismediatedbybrassinosteroidfeedbacksignaling.Curr.Biol.22,
1732–1737,http://dx.doi.org/10.1016/j.cub.2012.07.036.
Yuan,S.,Wu,Y.,Cosgrove,D.J.,2001.Afungalendoglucanasewithplantcellwall
extensionactivity.PlantPhysiol.127,324–333,http://dx.doi.org/10.1104/pp.
127.1.324.
Zykwinska,A.,Ralet,M.C.,Garnier,C.,Thibault,J.F.,2005.Evidenceforinvitro
bindingofpecticsidechainstocellulose.PlantPhysiol.139,397–407,http://
dx.doi.org/10.1104/pp.105.065912.
Zykwinska,A.,Thibault,J.-F.,Ralet,M.-C.,2007.Organizationofpecticarabinan
andgalactansidechainsinassociationwithcellulosemicrofibrilsinprimary
cellwallsandrelatedmodelsenvisaged.J.Expl.Bot.58,1795–1802,http://dx.
doi.org/10.1093/jxb/erm037.
Zykwinska,A.,Thibault,J.F.,Ralet,M.C.,2008.Competitivebindingofpectinand
xyloglucanwithprimarycellwallcellulose.Carbohydr.Polym.74,957–961,
