Patterns of Protein Synthesis and Tolerance of Anoxia in Roo(6)

Patterns of Protein Synthesis and Tolerance of Anoxia in Root

300Changetal.PlantPhysiol.Vol.122,2000

patternssuggeststhatproteinsmadelaterinanoxiainac-climatedroottipsdonotcontributetoimprovedtolerance.AnoxiaToleranceIsBlockedbyCycloheximideWhen

AddedduringHypoxicPretreatmentButNotWhenAddedduringAnoxia

Theobservationthatno“novel”proteinsweresynthe-sizedundereitherhypoxiaoranoxiawithinthescopeofthisstudyledustoexaminewhenproteinsynthesisisrequiredforacclimation.Proteinsynthesisinroottipsof

intactseedlingswasinhibitedwithcycloheximide(Ker-ridge,1958;LinandKey1967)addedduringeitherthehypoxicpretreatmentorthesubsequentanoxia.

Theefficacyofcycloheximidewasassessedfromincor-porationof[35S]Metintototalprotein,andtoleranceofanoxiawasassessedbyscoringviability.Cycloheximidesubstantiallyinhibitedproteinsynthesisinbothhypoxicandanoxicroottips(Fig.4,AandB).Intheabsenceofproteinsynthesisduringhypoxia,seedlingsdidnotsur-vivesubsequentanoxia(Fig.4C).Thisresultisconsistentwithearlierstudiesofacclimationinrootsandshoots

of

Figure4.Effectofcycloheximide(CHX),duringhypoxicpretreatmentorsubsequentanoxia,onproteinsynthesisandtolerance.Roottipsofin-tactmaizeseedlingsweretreatedwithincreas-ingconcentrationsofcycloheximidefor1hpriortoandduringeither4hofhypoxia(AandC)or13hofanoxia(BandD)(seeschematic,“Experimentalplan”).Proteinsynthesiswasmeasuredbyadding[35S]Metthroughouthy-poxia(A)andduringeitherthefirst( )orlast( )4hofanoxia(B).Datashownaremeans SE.Inmeasurementsofrootsurvival(CandD),seed-lingsweretreatedsequentiallywith4hofnor-moxia,4hofhypoxia,and13hofanoxia,followedbya26-hnormoxicrecoveryperiod;cycloheximidewasadded1hpriortoanddur-ingeither4hofhypoxia(C)or13hofanoxia(D).Cycloheximidewasremovedattheendofhypoxia(C)andanoxia(D).Growthdataaremeans SE(n 10–30);viabilitydataareag-gregatesoffourindependentexperimentsfromobservationsofatotalofupto80seedlingsforeachpoint.