Supply Route_ ABCG Transporters Act in the Construction of Suberin Barriers

ThePlantCell,Vol.26:3471,September2014,http://wendang.chazidian.comã2014AmericanSocietyofPlantBiologists.Allrightsreserved.

INBRIEF

SupplyRoute:ABCGTransportersActintheConstructionofSuberinBarriers

Plantsneedtoregulatethe owofwaterandsolutesbetweenthemselvesandtheirenvironment,bothaboveandbelowtheground.Toenablethis,plantsformdiffu-sionbarriersofhydrophobiccomponentswithinthecellwallmatrix(Nawrathetal.,2013).Suchapoplasticbarriersincludethecuticleinvegetativetissues,theCasparianstripinroots,andsuberin-containinglayersinvegetativeandroottissues.Diffusionbarriersalsoformatwoundsitesandduringabscission.Amongthemanyques-tionssurroundingtheformationofdiffusionbarriersishowthenecessaryhydrophobiccomponentsaretransportedoutsidethecell(Beissonetal.,2012).

TheATPbindingcassette(ABC)super-familyincludestransmembranetransportersinvolvedinaremarkablerangeofprocessesandisparticularlyexpandedinplants.Arabidopsisthalianahas.40membersintheABCGsubfamilyalone(Verrieretal.,2008).Althoughhighgeneticredundancyandfunctionaldivergencehinderdetermi-nationofABCproteinfunctions,someArabidopsisABCGfamilymembersareknowntobeinvolvedintheexportofcuticlecomponents.Now,Yadavetal.(2014)reportthatacladeofABCGproteinsinArabidopsisfunctionsinsuberinlayerformation.

Yadavetal.focusedonacladeinwhichallmembersarecoexpressedwithsuberinbiosynthesisgenes.Theyfoundthatthepromotersofall vegeneswereactiveinanthers/pollenandtherootendodermis(wherethesuberinbarrierisformed)andwereresponsivetowoundingaswellasabscisicacid.Fusionproteinsforeachlocalizedtotheplasmamembrane,con-sistentwitharoleincellularexport.Mutantanalysissuggestedthatmembersofonesubclade,ABCG1andABCG16,areimpor-tantinpollenwallformation.Triplemutantsdisruptedintheothersubclade,ABCG2,

http://wendang.chazidian.com/cgi/doi/10.1105/tpc.114.132290

ABCG6,andABCG20,resembledmutantsde cientinsuberin:Theirseedsandrootsystemshadincreasedpermeability(see gure).Inaddition,thesuberinlayerstructureandcomponentpro lewasaltered,indica-tingthatABCG2,ABCG6,andABCG20functioninrootstoexportsuberinlayercomponents,particularlythoseconferringimpermeability.

Inaniceparallel,Landgrafetal.(2014)recentlyfoundthatarelatedABCGtrans-porteractsinsuberinbarrierformationinpotato(http://wendang.chazidian.comndgrafetal.showedthatpotatoABCG1islocalizedtotheplasmamembraneandexpressedinrootsandtuberskin.TubersdownregulatedinABCG1hadalteredperidermandsuberincompositionandlostwatertwiceasfastasthewildtype.

St-ABCG1ismostsimilartoAt-ABCG1andAt-ABCG16amongalloftheABCtransportersinArabidopsis,suggestingthatthisentireclademighthaveaconserved

Rootsoftheabcg2abcg6abcg20triplemutantaremorepermeabletodye.Increasedstainingbypropidiumiodide(PI)inthesteleoftriplemutantrootscomparedwiththewildtype(Col).(AdaptedfromYadavetal.[2014],Figure4E.)

functioninsuberinbarrierformationinvarioustissues.Consistentwiththis,amemberofthesamecladefromrice(Oryzasativa)wasjustreportedalsotoplayaroleinsuberinbarrierformation(Shionoetal.,2014).Together,thesestudiesaddressoneofthebigques-tionsinsuberinlayerformation,namely,howthecomponentsgetoutsidethecell,andalsopromoteeffortstoassignfunctionstothewidearrayofABCtransporters.

NancyR.Hofmann

ScienceEditornhofmann@http://wendang.chazidian.com

ORCIDID:0000-0001-9504-1152

REFERENCES

Beisson,F.,Li-Beisson,Y.,andPollard,M.(2012).Solvingthepuzzlesofcutinandsuberinpolymerbiosynthesis.Curr.Opin.PlantBiol.15:329–337.

Landgraf,R.,etal.(2014).TheABCtransporterABCG1isrequiredforsuberinformationinpotatotuberperiderm.PlantCell26:3403–3415.

Nawrath,C.,Schreiber,L.,Franke,R.B.,Geldner,N.,Reina-Pinto,J.J.,andKunst,L.(2013).ApoplasticdiffusionbarriersinArabi-dopsis.TheArabidopsisBook11:e0167,doi/10.1199/tab.0167.

Shiono,K.,etal.(2014).RCN1/OsABCG5,anATP-bindingcassette(ABC)transporter,isrequiredforhypodermalsuberizationofrootsinrice(Oryzasativa).PlantJ.80:40–51.

Verrier,P.J.,etal.(2008).PlantABCproteins—auni ednomenclatureandupdatedinventory.TrendsPlantSci.13:151–159.

Yadav,V.,Molina,I.,Ranathunge,K.,Castillo,I.Q.,Rothstein,S.J.,andReed,J.W.(2014).ABCGtransportersarerequiredforsuberinandpollenwallextracellularbar-riersinArabidopsis.PlantCell26:3569–

3588.

Supply Route: ABCG Transporters Act in the Construction of Suberin Barriers

Nancy R. Hofmann

Plant Cell 2014;26;3471; originally published online September 23, 2014;

DOI 10.1105/tpc.114.132290

This information is current as of February 8, 2015

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