Cadmium inhibits the induction of high-affinity nitrate uptake

Planta

DOI10.1007/s00425-012-1729-4

ORIGINALARTICLE

Cadmiuminhibitstheinductionofhigh-af nitynitrateuptakeinmaize(ZeamaysL.)roots

CeciliaRizzardo NicolaTomasi RossellaMonte

ZenoVaranini FabioF.Nocito StefanoCesco RobertoPinton

Received:28May2012/Accepted:17July2012ÓSpringer-Verlag2012

AbstractCadmium(Cd)detoxi cationinvolvesgluta-thioneandphytochelatinsbiosynthesis:thehigherneedofnitrogenshouldrequireincreasednitrate(NO3-)uptakeandmetabolism.Weinvestigatedinduciblehigh-af nityNO3-uptakeacrosstheplasmamembrane(PM)inmaizeseedlingsrootsuponshortexposure(10minto24h)to

ElectronicsupplementarymaterialTheonlineversionofthisarticle(doi:10.1007/s00425-012-1729-4)containssupplementarymaterial,whichisavailabletoauthorizedusers.

C.RizzardoÁF.F.Nocito

DipartimentodiScienzeAgrarieeAmbientali,Universita

`degliStudidiMilano,ViaCeloria2,20133Milan,Italye-mail:cecilia.rizzardo@unimi.itF.F.Nocito

e-mail:fabio.nocito@unimi.it

N.TomasiÁR.MonteÁR.Pinton(&)

DipartimentodiScienzeAgrarieeAmbientali,Universita

`degliStudidiUdine,ViadelleScienze208,33100Udine,Italye-mail:roberto.pinton@uniud.itN.Tomasi

e-mail:nicola.tomasi@uniud.itR.Monte

e-mail:rossella.monte@uniud.it

Z.Varanini

DipartimentodiBiotecnologie,Universita

`degliStudidiVerona,VillaLebrecht,ViadellaPieve70,37029SanFloriano,VR,Italy

e-mail:zeno.varanini@univr.it

S.Cesco

Facolta

`diScienzeeTecnologie,LiberaUniversita`diBozen-Bolzano,PiazzaUniversita

`1,39100Bozen-Bolzano,Italye-mail:stefano.cesco@unibz.it

lowCdconcentrations(0,1or10lM):theactivityandgenetranscriptabundanceofhigh-af nityNO3-trans-porters,NO3-reductasesandPMH?-ATPaseswereanalyzed.Exposureto1mMNO3-ledtoapeakinhigh-af nity(0.2mM)NO3-uptakerate(induction),whichwasmarkedlyloweredinCd-treatedroots.PlasmamembraneH?-ATPaseactivitywasalsostronglylimited,whileinternalNO3-accumulationandNO3-reductaseactivityinextractsofCdtreatedrootswereonlyslightlylowered.Kineticsofhigh-andlow-af nityNO3-uptakeshowedthatCdrapidly(10min)blockedtheinduciblehigh-af n-itytransportsystem;theconstitutivehigh-af nitytransportsystemappearednotvulnerabletoCdandthelow-af nitytransportsystemappearedtobelessaffectedandonlyafteraprolongedexposure(12h).Cd-treatmentalsomodi edtranscriptlevelsofgenesencodinghigh-af nityNO3-transporters(ZmNTR2.1,ZmNRT2.2),PMH?-ATPases(ZmMHA3,ZmMHA4)andNO3-reductases(ZmNR1,ZmNADH:NR).DespiteanexpectableincreaseinNO3-demand,anegativeeffectofCdonNO3-nutritionisreported.Cdeffectresultsinalterationsatthephysiologi-calandtranscriptionallevelsofNO3-uptakefromtheexternalsolutionanditisparticularlysevereontheinduciblehigh-af nityaniontransportsystem.Further-more,CdwouldlimitthecapacityoftheplanttorespondtochangesinNO3-availability.

KeywordsATPaseÁCadmiumÁNitratereductaseÁNitrogenacquisitionÁNitratetransportersNRTAbbreviationsCdCadmiumGDHGlutamatedehydrogenase

NO3-NitrateNRNitrate

reductase

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