78-Metabolic-profiling-of-root-exudates-of-Arabidopsis-thalian

MetabolicProfilingofRootExudatesofArabidopsisthalianaTRAVISS.WALKER,†HARSHPALBAIS,†KATHLEENM.HALLIGAN,‡FRANKR.STERMITZ,‡ANDJORGEM.VIVANCO*,†DepartmentofHorticultureandLandscapeArchitectureandDepartmentofChemistry,ColoradoStateUniversity,FortCollins,Colorado80523-1173Inadditiontoaccumulatingbiologicallyactivechemicals,plantrootscontinuouslyproduceandsecretecompoundsintotheirimmediaterhizosphere.However,themechanismsthatdriveandregulaterootsecretionofsecondarymetabolitesarenotfullyunderstood.Toenlightentwoneglectedareasofrootbiology,rootsecretionandsecondarymetabolism,aninvitrosystemimplementingroot-specificelicitationovera48-daytimecoursewasdeveloped.AfterrootsofArabidopsisthalianahadbeenelicitedwithsalicylicacid,jasmonicacid,chitosan,andtwofungalcellwallelicitors,thesecondarymetabolitessubsequentlysecretedwereprofiled.High-performanceliquidchromatographywasusedtometabolicallyprofilecompoundsintherootexudates,and289possiblesecondarymetaboliteswerequantified.Thechemicalstructuresof10compoundswerefurthercharacterizedby1Hand13CNMR:butanoicacid,trans-cinnamicacid,o-coumaricacid,p-coumaricacid,ferulicacid,p-hydroxybenzamide,methylp-hydroxybenzoate,3-indolepropanoicacid,syringicacid,andvanillicacid.Severalofthesecompoundsexhibitedawiderangeofantimicrobialactivityagainstbothsoil-bornebacteriaandfungiattheconcentrationdetectedintherootexudates.KEYWORDS:Arabidopsisthaliana;Brassicaceae;butanoicacid;trans-cinnamicacid;o-coumaricacid;p-coumaricacid;ferulicacid;p-hydroxybenzamide;methylp-hydroxybenzoate;3-indolepropanoicacid;syringicacid;vanillicacid;elicitationINTRODUCTIONThehiddenhalfofaplantsystemthrivesinadiverse,ever-changingenvironmentwithbacteria,fungi,andothermicroor-ganismsfeedingonanarrayoforganicmaterial(1).Thus,theareaofsoilsurroundingaplantrootrepresentsauniquephysical,biochemical,andecologicalinterfacebetweentherootsandtheexternalenvironment.Thisso-calledrhizosphereisinpartregulatedbytherootsystemitselfthroughchemicalsexuded/secretedintothesurroundingsoil.Rootexuda