第六节 乙烯

乙烯的发现 1901年俄罗斯圣匹得堡植物研究所的一位学者DimitryNeljubow 煤气和实验室气体 三重反应 tripleresponse 1910年H H Cousins向牙买加农业部 香蕉和柑桔的存放1934年 R Gane等 乙烯是内源气态植物激素的确认1959年气相色谱被用于乙烯的研究 乙烯作为植物激素的重要地位才被人们重新认识 IlluminatinggasinjuryonAcersaccharum 糖槭 乙烯及其代谢物的化学结构 生物乙烯的合成部位和发生特点 叶片脱落 花器官衰老或者果实成熟以及逆境因素都会诱导植物体内乙烯的大量合成 乙烯在极低浓度 1pLL 1 下就具有显著的生物效应 成熟苹果组织内的乙烯浓度高达2500pLL 1 幼嫩叶片的乙烯发生量比成熟叶片乙烯发生量要大得多 11 Factorsaffectingethylenebiosynthesis developmentalstate fruitripening environmentalconditions stress physicalandchemicalinjuryotherplanthormones auxin cytokinin someorganicandinorganicchemicals 乙烯生物合成的影响因素 auxinpromotesethylenebiosynthesisbyenhancingACCsynthaseactivityPosttranscriptionalregulationofethyleneproductionbyCytokinin AuxinandCytokinininducedethyleneproduction AgNO3Ag S2O3 23 STS CO2 highconc 1 methlcyclopropenetrans cyclooctene Inhibitorsofethyleneaction Theethylenecell membranereceptorproteinappearstoincludeacoppercofactorandcanalsobeeliminatedwhenthereceptorbindstosilver Ag ionsusuallysuppliedassilverthiosulfate Thesilverthiosulfatecanthusbeaddedtoavasetoincreasethevase lifeofabouquetofflowers ASimplifiedModelDepictingtheInductionofEthyleneBiosynthesisandtheDownstreamEthyleneSensing SignalingPathway Ethylenebiosynthesisisinducedinresponsetoavarietyofendogenousandenvironmentalcues Oneoftheearlyresponsesafterthesensingofthesecuesistheinductionofethylene whichisachievedviaupregulationofACSactivity therate limitingenzymethatcatalyzesthefirstcommittedstepofethylenebiosynthesis MembersinthetwomajorsubgroupsoftheACSfamily representedbyACS5andACS6 areregulatedbydifferentkinasepathways PhosphorylationstabilizesACS6 andpossiblyACS5 andinteractionofACS5withETO1 andperhapsotherunknowncomponents targetsACS5fordegradationbytheproteasome Fine tuningofethyleneinductionisachievedbytissue specificexpression geneactivation andtheformationofheterodimersbetweendifferentACSmembers ACCoxidase ACO activitycanalsoaffectlevelsofethyleneinduction EthylenegasisperceivedbyafamilyofER associatedreceptors ETR1 ETR2 ERS1 ERS2 andEIN4 CTR1 anegativeregulatorofdownstreamresponses isproposedtobeactivatedbytheunoccupiedreceptorsviaphysicalinteractionandisinhibiteduponbindingofethylenebythereceptor CTR1mayfunctionthroughunidentifiedMAPKK s andMAPK s Downstreamcomponentsintheethylenepathwayincludeseveralpositiveregulators EIN2 EIN5 EIN6 andEIN3 Intheabsenceofethylene EIN3proteinistargetedfordegradationbyanSCFcomplexcontainingoneofthetwoF boxproteins EBF1andEBF2 Inthepresenceofethylene EIN3accumulatesinthenucleusandactivatesgeneexpression whicheventuallyleadstoethylene inducedresponses LiuandZhangpresentstrongevidencethatlandstheMPK6MAPKmoduleinthepathwayregulatingACS6activity upstreamofethylenebiosynthesisinresponsetostress ModelfortheregulationofethylenebiosynthesisbyETO1NotethatACS5formsadimerwithtwocatalyticsitessharedbythetwomonomers Thereddotsintheactivesitesindicatetheessentialcofactorpyridoxal 5 phosphate a IntheabsenceofeithertheCterminusofACS5 eto2 1 ortheintactETO1protein eto1 1 ethyleneisoverproduced b RegulationofACS5activitybyETO1 ETO1interactswithACS5andinhibitsenzymeactivity ACSinactivationmechanism ACS5issubjectedtoproteasome dependentproteindegradationthroughtheinteractionwithETO1 ACSdegradationmechanism whichinteractswithCUL3oftheubiquitinE3ligase ThereversiblemodificationoftheCterminusofACS5byasyetunknownproteinsisproposedtoregulatetheinteractionbetweenETO1andACS5 Fromthefollowingarticle RegulationofethylenegasbiosynthesisbytheArabidopsisETO1proteinKevinL C Wang HitoshiYoshida ClaireLurinandJosephR EckerNature428 945 950 29April2004 乙烯的生理功能PhysiologicalRolesofEthylene 三重反应tripleresponse促进果实的成熟Stimulatesfruitripening 促进叶片和花瓣衰老Stimulatesflowerandleafsenescence乙烯促进叶片和果实脱落Stimulatesleafandfruitabscission诱导不定根和根毛发生Induceadventitiousrootandroothireformation TripleResponse 乙烯促进叶片的偏上生长 乙烯诱导落叶 Modelofhormonalcontrolofleafabscission Highauxinfromleafreducesethylenesensitivityofabscissionzoneandpreventsleafshedding Areductioninauxinfromtheleafincreasesethyleneproductionandethylenesensitivityintheabscissionzone whichtriggersthesheddingphase Synthesisofenzymesthathydrolyzethecellwallpolysaccharides resultingincellseparationandleafabscission 28 Effectofethyleneonabscissioninbirch WT Transgenic Transgenic birchplanttransformedwithmutatedversionofArabidopsisethylenereceptor ETR1Transgenicplantsdonotdroptheirleaveswhensprayedwith50ppmofethylene WT 乙烯与离层的形成 纤维素酶反义mRNA免疫染色 离层 Abscissionzone Ethyleneduringfloweringandfruitripening Ethylenewasfirstdetectedasflowerbudsopenedandexhibiteddiurnaloscillationswithpeakproductionpriortopetalabscission AfterthatC2H4productionfellstoalowandrelativelycontinuousleveluntilfruithadenteredthelatterstagesofbeingnon expandedanddark green Oncefruitinitiatedredcoloration C2H4releasebecomeselevatedinalinearfashion withoutdiurnalfluctuations 乙烯促进花瓣的衰老 HansKende EthyleneproductionandaccoxidasegeneexpressionduringfruitripeningofCoffeaarabicaL Braz J PlantPhysiol vol 17no 3LondrinaJuly Sept 2005 乙烯与耐储藏西红柿 乙烯诱导根毛的形成 乙烯促进不定根形成 Ethylenereceptors etr1anethylene insensitivemutant Arabidopsisseedlingsgrowninthepresenceofethylene Notripleresponse Tripleresponse ETR1encodestwo componenthistidinekinase firsteukaryotichistidinekinase ETR1mightbeanethylenereceptor etr1 ethyleneresistant1 EthylenereceptorsinArabidopsis ArabidopsisgenomeencodesfouradditionalproteinssimilartoETR1 whichallbindethylene ERSETR1 RELATEDSEQUENCE EINETHYLENE INSENSITIVE 3 4transmembranedomains cGMP bindingdomain Biochemicalmechanismunknown Biochemicalmechanismunknown WT C2H4 WT C2H4 A B C D The5Arabidopsisethylenereceptorsarefunctionallyredundant Aserine threoninekinaseisalsoinvolvedinethylenesignaling ctr1 constitutivetripleresponse1intheabsenceofethylene Arabidopsisseedlingsgrownindarkinairfor3d ctr1 CTR1 relatedtoRAF 1 aMAPKKKserine threonineproteinkinease mitogen activatedproteinkinasekinasekinase Othercomponentsintheethylenesignalingpathway EIN3transcriptionfactorsKeycomponentsinmediatingethyleneeffectongenetranscriptioninresponsetoethylene homodimersofEIN3bindtopromoterofERFERF1 ETHYLENERESPONSEFACTOR1 ERFsencodeproteinsbelongingtoERE ETHYLENERESPONSEELEMENT bindingproteins afamilyoftranscriptionfactors ModelofethylenesignalinginArabidopsis RAN1requiredtoassemblecoppercofactorintoethylenereceptor Inabsenceofethylene ETR1andotherreceptorsactivateCTR1kinase repressionofethyleneresponsesthroughMAPKcascade Inpresenceofethylene bindingofethylenetoreceptorsresultsintheirinactivation causingCTR1tobecomeinactive InactivationofCTR1allowsEIN2tobecomeactive ActivationofEIN2turnsonEIN3transcriptionfactors whichinduceexpressionofERF1 changesingeneexpression alterationsincellfunctions 拟南芥乙烯信号传导模型 AmodeloftheroleofEIN5intheethylenesignaltransductionpathway Ethylene C2H4 isperceivedbyrepressingtheactionofreceptorcomplexesincludingETR ERS EIN4receptors RTE1 andRaf likeproteinkinaseCTR1 whichnegativelyregulatesdownstreamsignalingcomponentEIN2 Uponethylenetreatment EIN2isderepressedandcouldthustransmitthesignalintothenucleustoactivateanumberoftranscriptionfactors includingEIN3andEIL1 EIN3directlybindstotheregulatoryelementsoftargetgenesandinducestheexpressionofyetothertranscriptionfactors i e ERFsandEDFs thatwouldultimatelyregulateaseriesofethyleneresponses Intheabsenceofethylenesignal aSkp1 Cu