A)pecarb.OmninorpathwayaCOOHPeroxidaseNNHHindole-3-acetic acid3-Methyleneoxindole(B)Nondecarboxylation pathwaysConjugationBiAspartateindole-3-acetylaspartateNHAiAspartateNHDioxindole-3-acetylaspartateCOOHHFigure 8-7Oxindole-3-aceticacid(OXIAAFigure 19.11BiodegradationoflAA.(A)Theperoxidaseroute(decarboxylationpathway)piaysareiativeiyminorrole.(B)Thetwonondecarboxyiationroutes ofiAAoxidative degradation.A and B,are themostcommonmetaboiicpathways.(After Tuominenet al.1994.)
Figure 8-7
1.Intheabsence3.Inthepresenceof5.IAA-inducedoflAA,theauxin,AUX/AAdegradationofthetranscriptionproteinsaretargetedAUxiAAproteinsfactor,ARF,formsfordestruction byanallows active ARFinactiveIAAactivated ubiquitinhomodimerstoheterodimers withligase.form.AUX/IAAproteins.SignalActiveARFtransductionInactiveARFhomodimerpathwayheterodimerARFARFARFActivationofAUXIAADNAubiquitin ligaseTGTCTCCTCTGTPalindromicAuxREATPUbiquitin6.TheactiveARFAUXiIAAandhomodimersbindtoother earlygenespalindromicAuxREsin4.TheAUXIAAthepromotersofthe2.Inactive hetero-proteins aretaggedUbiearlygenes,activatingdimersblockthewithubiquitinandtranscription,transcriptionofthedegradedbytheAUXIAAearly auxingenes.26Sproteasome.AUXllAAandThere is no auxinother earlygenesresponse.8.The stimulationof AUXlIAAgenesintroducesaAuxin-mediatednegativefeedbackgrowth/developmentloop.Figure 8-9Proteasome7.Transcriptionofthe early genesinitiatestheauxinresponse.FIGURE19.41Amodel forauxin regulation of transcriptionalactivation of earlyresponsegenesbyauxin.(AfterGrayetal200l.)
Figure 8-9
Figure 8-10-1Auxin and root development on stemcuttings.(Left)Many adventitious roots developed on ahoneysuckle (Lonicera fragrantissima)cuttingplaced in asolution with a high concentration of synthetic auxin.(Middle)Fewerrootsdevelopedin alowerauxinconcentration.(Right)The cuttingplaced in water (noauxin) served as a control and did not form roots in thesame time period.Joe Eakes,Color Advantage/VisualsUnlimited)
Figure 8-10-1
Turgorpressure stretchesweakenedcell wall.HOAuxinbindstoplasmaActivatedprotonpumpsmembranereceptors.transportHtoutofcellcell wallplasmamembraneATP-H+ATPcytoplasmATPH+4receptor.ATPATP+H+H+auxinAuxinmodeofaction.Afterauxinbindstoareceptor,thecombinationstimulatestheprotonpumpsothathydrogenions (H')aretransported outofthecell.Theresultingacidity causes the cell walltoweaken,andthe electrochemicalgradient causes solutesto enterthecell.Waterfollowsbyosmosisandthecell elongatesFigure 8-10-2
Figure 8-10-2
StageOppPLASTIDGGPPenf.onaidinhosnhateeneO1Stage 2COOHCHOOOHCH,COOHOOHCOOHent-KaureneGA-aldehydeGAGAsENDOPLASMICRETICULUMStage3CYTOSOLCThethree stagesofgibberellinbiosynthesis.InFIGURE20.6stage1,geranyigeranyidiphosphate(Gcrp)isconvertedtoCOOHent-kaurenevlacopalyidiphosphate(Cpp)inplastids.InCOOHstage2,whichtakesplace ontheendoplasmicreticulum,GA(R-H)enf-kaurereSconvertedtoGAorCAadependingonGA(ROH)atcarbon13.InmostwhethertheCAishydroxylateplants theT3-hydroxvlationpathwaypredomintes,thoughthonon-13-oHpathwayisinArubidopsisandsomeothersGA20-oxidasecytonolGAiaorGAathemainpathwaystaeRThisconversionprceedswithaareconvertedotherGAs2IntheIa-hydroxvlationseriosofoxidationsatcarDrHOCpathway this leads tothe production of GA2gGAap.isthenoxidizedtotheactivegibberellin,GAbyaSp-hydroxyla-tion reaction(thu non-T3OH equivalent is GAFinallyCOOHhydroxylationatcarbon2convertsGAanand GA,totheCOOHinactiveformsCAaoatdGArespectivelyGAIS-OL(R=H)GA4-OL(R-OH)GAZ0-oxidaseACLiveGAGAoxidaseGA20-oxidaseHCOOHCOOHCOOHGA(RH)GA.(R-H)COOHGA(R=OH)GA20(R=OH)GA24(R-H)GA(R-OH)GA2-oxidaseGA2-oxidaseinactivation1FFigure 8-13HOHCHCCOOHCOOHGA(R-H)GASI(RWH)GA(R-OH)GA2(R=OH)
Figure 8-13