PlantHormoneSignal

transductionpathway

TalkOutlineGeneralintroductiontocellsignalingtransductionpathwaysinplant.Differentplanthormonesandtheirphysiologicalfunctioninplants.Comparisonbetweenplanthormonesandanimalhormonesaction.Waysorapproachesinstudyingplanthormonesignalingtransductionpathways.Molecularmechanismofvariousplanthormonesignaltransductionpathways(a)ubiquitin-dependentproteindegradation

(negativeregulator)(b)towcomponentsystem(phospho-relay).

6.

Manipulationofplantgrowthanddevelopmentwithknowledgefromplanthormonesignaltransductionpathway.ex.Secondgreenrevolution.AnalogyviewofcellsignalingtransductionpathwayInput(command)KeyboardSignalperceptionEndogenous:phytohormoneExogenous:environmentalcueCPU(CentralProcessingUnit)ChipSignalTransduction

NetworkCompiling,Integration,processingOutput(performance)PrinterSignalResponseMorphogenesischange,GrowthdevelopmentdifferentiationVarioussignalingtransductionpathwaysinplantsCalcium(Ca+2)signaling(regulatorynetwork)LipidsignalingtransductionpathwayReactiveoxygenspecies(ROS)signalingNitricoxide(NO)signalingtransductionpathwaySugarsensingresponsivepathwayWounding-signaltransductionpathway(plant-pathogeninteraction)LightsignalingresponsivepathwayBiologicalo’clock(circadianrhythm)regulatorypathwayDevelopmentregulatorypathwaye.g.flowering(autonomous),lead,root,trichomeformationrootapicalmeristem(RAM)shootapicalmeristem(SAM)formationpolarityandcellcytoskeletonrearrangement

Specificcellfatedeterminationanddifferentiation(Xylemandphloemspecification,rootorganization(patterning))Abioticstresssignalingpathways(salt,drought,heat,cold,metal,vernalizationetc.)Planthormonesignalingtransduction(auxin,ethylene,cytokinin,gibberellin,abscisicacid,brasinosteroid,jasmonicacidetc.)DefinitionofplanthormoneThewordhormoneisderivedfromtheGreekverbmeaningtoexcite.hormonesareorganicsubstancessynthesizedinonetissueandtransportedoutwheretheirpresenceresultsinphysiologicalresponses(notalwaystrue;mayactatorclosetosynthesissite).Theyarerequiredinminuteamounts(10-6to10-8M).3. Eachhormonemayresultinmultipleeffects--theparticulareffectdependingonanumberoffactors:(a)thepresenceofotherhormonesandthepresenceofactivatormolecules(calcium,sugars)(b)theamountofthehormone(dosageorconcentration)(c)thesensitivityofthattissuetothehormone.(d)theconditionoftheplantitselfiscritical:whatistheconditionoftheplant?itsage?

Siteofactionxdevelopmentalstagexconcentrationofhormone?Crosstalkandspecificity?

planthormonessynthesissitesandtheirmajorfunctionsEffectsofplanthormonesonplantgrowthanddevelopmentEmbryogenesis(Celldivision,expansion,differentiationandcelldeath)SenescenceWhatisthedifferencebetweenplanthormonesandanimalhormones?Science,2001DissectplanthormonesignaltransductionpathwaysbymoleculargeneticanalysisSummaryofmolecularcomponentsinvolved

inplanthormonesignalingtransduction

Auxin:

TIR1:F-boxprotein(Ubiquitinconjugatedligase) PIN1(pin-formed1) Aux/IAArepressorEthylene:histidinekinaseRaf-likekinaseCTR1MitogenactivatedproteinkinasecascadeCytokinin: phosphorelay(two-componentsystem)4. Gibberellin: GproteinandDELLAprotein hexosamine(NAcGlu)5. Abscisicacid: PP2Cprotein,SnRKproteinkinase FarnesylationBrasinosteroid:BRI1(LRR-RLK)Anoverviewoftheubiquitinationprocess

inplantsAnnalsofBotany99:787-822(2007)E1;UBA,ubiquitinactivatingenzymeE2:UBC,ubiquitinconjugatingenzymeE3:ubiquitinproteinligaseRBX:ring-boxproteinCUL:cullinCRL:cullinringligaseHECT:homologoustoE6-APCOOHterminusRING:reallyinterestingnewgeneproteindomainSCF:SKP1-Cullin-F-boxSKP:SphasekinaseassociatedproteinF-box:SKP/ASKinteractionmotifincyclinFBiologicalsignificanceofubiquitin/proteosomesystem(UPS)inplantsUPSwasinvolvedindifferentprocessesofplantlife,includingorganinitiationandembryogenesispatterning,lightsignalling,circadianclockregulation,hormoneproduction,perceptionandsignaltransduction,andinplantdefence.2. Thecovalentattachmentofubiquitintoasubstrateproteinchangesitsfate.Notably,proteinstypicallytaggedwithalysine48-linkedpolyubiquitinchainbecomesubstratesfordegradationbythe26S

proteasome.Over6%(1,500genes)ofthepredictedarabidopsisgenomeencodesproteinsinvolvedintheUPS,andanalysesofotherplantgenomesdemonstrateasimilarabundanceofUPS-relatedgenes. E1(1);E2(1);UEV(8);E3(mastabundant):HECT(7);Ring(450);U-domain(61);cullin(11);F-box(700)BTB(80)CrystalstructureoftheTIR1–ASK1complexwithauxinandtheIAA7degronpeptideauxinfunctionasa‘molecularglue’toenhanceTIR1–substrateinteractionsNature446,2007Phenotypesassociatedwiththeauxin

andgibberellinreceptormutants

Development133,1857-1869(2006)Phenotypesassociatedwiththebrassinosteroid,

ethylene,cytokininandabscisicacidreceptormutants

Development133,18