1、STRIGOLACTONESStrigolactones contribute to a devastating form of plant parasitismStrigaareparasiticplantsthatarethesingle largest biotic cause ofreducedcropyieldsthroughoutAfrica($10billionperyearinyieldlosses)StrigaHostRoot parasitesStrigagerminationisinducedbystrigolactonesproducedbythehostplantro
2、otsStriga hermonthicaImage source:USDA APHIS PPQ ArchiveStrigolactones(SLs)regulate seemingly unrelated eventsStrigaHostRootAMfungiSLsinhibitshootbranchingSLspromoteassociationswitharbuscularmycorrhizal(AM)fungiSLspromotegerminationofparasiticStrigaplantsStrigolactones inhibit shoot branchingImage c
3、ourtesy RIKENWildtypeSL-deficientInmutantplantsunabletomakeSLs,manymoreshootbranchesgrowoutStrirgolactones promote beneficial symbiotic interactionsImage courtesy of Mark BrundrettSymbiotic AM fungiSLspromotesthesymbioticassociationwithAMfungi.Thissymbiosisoccursin80%oflandplantsandhelpsthemassimila
4、tenutrientsfromthesoilArbuscularisderivedfromLatinfortree(arbor).Mycorrhizameans“fungusroot”Strigolatones promote germination of parasitic Striga seedsStriga-infestedmaizefieldTheircommonnameiswitchweedbecausetheplantsappeartobecursed.TypicallyStrigainfestationcausesreductionsincropyieldsof50100%Ima
5、ge source USDA APHIS PPQ Archive Image courtesy RIKENWhatistheconnectionbetween:ShootbranchingRootparasitism,andRootsymbiosis?These three independent topics recently converged on SLsEvolutionofplantparasitismOriginsofplant/mycorrhizalsymbiosis460myaSearchforbranchingfactor.1960s1970sPurificationandc
6、haracterizationofstrigolfromroots1900s-Roleofauxininshootbranchingdescribed1990s2000sBranchingmutantsdescribedinpetunia,pea,Arabidopsisandrice2008-Strigolactones inhibit shoot branching1800s-RecognitionofAM/plantsymbiosis1800s-Hostplantfactorrequiredforparasiticseedgermination2005-Strigolactones pro
7、mote hyphal branchingLecture OutlineSynthesisPerceptionandsignalingStrigolactonesinwhole-plantprocesses:ShootbranchingMosscolonygrowthSymbiosisGerminationTowardstheeliminationofStrigaparasitismImage source USDA APHIS PPQ Archive SynthesisInasearchforstimulatorsofStrigagermination,strigolactoneswerep
8、urifiedfromcottonrootsin1966andthechemicalstructuredeterminedin1972Cook,C.E.,Whichard,L.P.,Turner,B.,Wall,M.E.,and Egley,G.H.(1966).Germination of witchweed(Striga lutea Lour.):Isolation and properties of a potent stimulant.Science 154:1189-1190;Reprinted with permission from Cook,C.E.,Whichard,L.P.
9、Wall,M.,Egley,G.H.,Coggon,P.,Luhan,P.A.,and McPhail,A.T.(1972).Germination stimulants.II.Structure of strigol,a potent seed germination stimulant for witchweed(Striga lutea).J.Am.Chem.Soc.94:6198-6199.Strigolactones(SLs)are a small family of compoundsReprinted from Humphrey,A.J.,and Beale,M.H.(2006
10、).Strigol:Biogenesis and physiological activity.Phytochemistry 67:636-640 with permission from Elsevier.5-DeoxystrigolSYNTHESISTherearemanynaturallyoccurringSLs,derivedfrom5-deoxystrigolThe stimulator of Striga germination derives from the carotenoid pathwayfluridoneMEPpathwayGGPPphytoeneb-carotene5
11、deoxystrigolCarotenoid-deficientmutantsdonotmakegerminationstimulatorWTWTmutantmutantThroughtheuseofmaizemutantsandenzymeinhibitors,carotenoidsweredemonstratedtobetheprecursorsofSLsMatusova,R.,Rani,K.,Verstappen,F.W.A.,Franssen,M.C.R.,Beale,M.H.,and Bouwmeester,H.J.(2005).The strigolactone germinat
12、ion stimulants of the plant-parasitic Striga and Orobanche spp.are derived from the carotenoid pathway.Plant Physiol.139:920-934.Genes involved in SL biosynthesis were identified by genetic methodsReprinted from Booker,J.,et al.(2004).MAX3/CCD7 is a carotenoid cleavage dioxygenase required for the s
13、ynthesis of a novel plant signaling molecule.Curr.Biol.14:1232-1238 with permission from Elsevier;Morris,S.E.,et al.(2001).Mutational analysis of branching in pea.Evidence that Rms1 and Rms5 regulate the same novel signal.Plant Physiol.126:1205-1213;Ishikawa,S.,et al.(2005).Suppression of tiller bud
14、 activity in tillering dwarf mutants of rice.Plant Cell Physiol.46:79-86 by permission of the Japanese Society of Plant Physiologists.Simons,J.L.,et al.(2007).Analysis of the DECREASED APICAL DOMINANCE genes of petunia in the control of axillary branching.Plant Physiol.143:697-706.WTmax3WTrms5Strigo
15、lactone-deficientmutantsinArabidopsis,pea,riceandpetuniashowsimilarshort,branchyphenotypesTheMORE AXILLARY GROWTH3(MAX3),RAMOSUS5(RMS5),DWARF17(D17)andDECREASEDAPICALDOMINANCE3(DAD3)genesallencodeacarotenoidcleavagedioxygenase(CCD7)WTdad3SL biosynthesis pathway(so far)Umehara,M.,Hanada,A.,Yoshida,S.
16、Akiyama,K.,Arite,T.,Takeda-Kamiya,N.,Magome,H.,Kamiya,Y.,Shirasu,K.,Yoneyama,K.,Kyozuka,J.,and Yamaguchi,S.(2008).Inhibition of shoot branching by new terpenoid plant hormones.Nature 455:195-200.CarotenoidcleavageproductMAX3,RMS5,D17,DAD3MAX4,RMS1,D10,DAD1 MAX1STRIGOLACTONES(CCD7)(CCD8)(P450)MAX;Ar
17、abidopsisRMS;peaD;riceDAD;petuniaTheremustbeadditional,uncharacterizedstepsThesereactionsoccurintheplastidD27Rice SL biosynthesis mutants are rescued by exogenous SLControl2ndleaftiller1stleaftiller1cm1cmWT d10 d17 WT d10 d17 GR24(1M)d10andd17arerescuedbyexogenousSL(GR24isasyntheticSL)Cleavageproduc
18、tD10(CCD7)(CCD8)D17InhibitionofshootbranchingCarotenoidStrigolactoneorSLmetaboliteUmehara,M.,Hanada,A.,Yoshida,S.,Akiyama,K.,Arite,T.,Takeda-Kamiya,N.,Magome,H.,Kamiya,Y.,Shirasu,K.,Yoneyama,K.,Kyozuka,J.,and Yamaguchi,S.(2008).Inhibition of shoot branching by new terpenoid plant hormones.Nature 455
19、195-200.WTmax1max3max4ControlGR24(5M)MAX1(P450)CleavageproductD10(CCD7)(CCD8)D17InhibitionofshootbranchingMAX3MAX4CarotenoidStrigolactoneorSLmetaboliteArabidopsis SL biosynthesis mutants are rescued by SLUmehara,M.,Hanada,A.,Yoshida,S.,Akiyama,K.,Arite,T.,Takeda-Kamiya,N.,Magome,H.,Kamiya,Y.,Shiras
20、u,K.,Yoneyama,K.,Kyozuka,J.,and Yamaguchi,S.(2008).Inhibition of shoot branching by new terpenoid plant hormones.Nature 455:195-200.MAX1 encodes a P450 enzyme shown in Arabidopsis to affect shoot branchingReprinted from Booker,J.,Sieberer,T.,Wright,W.,Williamson,L.,Willett,B.,Stirnberg,P.,Turnbull,C
21、Srinivasan,M.,Goddard,P.,and Leyser,O.(2005).MAX1 encodes a cytochrome P450 family member that acts downstream of MAX3/4 to produce a carotenoid-derived branch-inhibiting hormone.Developmental Cell 8:443-449 with permission from Elsevier.max1WTMAX1 isexpressedthroughouttheplantprimarilyinassociati
22、onwithvasculartissuesD27 also encodes a protein necessary for SL synthesisLin,H.,Wang,R.,Qian,Q.,Yan,M.,Meng,X.,Fu,Z.,Yan,C.,Jiang,B.,Su,Z.,Li,J.and Wang,Y.(2009).DWARF27,an iron-containing protein required for the biosynthesis of strigolactones,regulates rice tiller bud outgrowth.Plant Cell.21:1512
23、1525.Wild-type(Shiokari)d27Strigolactonesaredetectedinexudatesofwild-typebutnotd27rootsStandardWild-typeexudated27exudateD27-likeproteinsarefoundinotherplantsaswellasriceSLs synthesis in root or shoot is sufficient to control shoot branchingBooker,J.,Sieberer,T.,Wright,W.,Williamson,L.,Willett,B.,S
24、tirnberg,P.,Turnbull,C.,Srinivasan,M.,Goddard,P.,and Leyser,O.(2005).MAX1 encodes a cytochrome P450 family member that acts downstream of MAX3/4 to produce a carotenoid-derived branch-inhibiting hormone.Developmental Cell 8:443-449.max3WTmax3ScionRootWTmax3WTGraftsReciprocalgrafts,inwhichwild-typeti
25、ssueiseithertherootorscion,havenormalphenotypes;thissaysthatthebranch-controllingsignalcanbemadeineithertissue,andcanmovefromroottoshootBooker,J.,Sieberer,T.,Wright,W.,Williamson,L.,Willett,B.,Stirnberg,P.,Turnbull,C.,Srinivasan,M.,Goddard,P.,and Leyser,O.(2005).MAX1 encodes a cytochrome P450 family
26、 member that acts downstream of MAX3/4 to produce a carotenoid-derived branch-inhibiting hormone.Developmental Cell 8:443-449.An intermediate between MAX4 and MAX1 action can movemax4max1max1max4MAX1STRIGOLACTONESMAX4Inthisexperimentmobile,graft-transmissibleintermediateinSLsynthesisisproducedinmax1
27、shoots,andconvertedintoSLinthemax4shoots.Synthesis-summaryUmehara,M.,Hanada,A.,Magome,H.,Takeda-Kamiya,N.,and Yamaguchi,S.(2010).Contribution of strigolactones to the inhibition of tiller bud outgrowth under phosphate deficiency in rice.Plant Cell Physiol.51:1118-1126.SLsarederivedfromcarotenoidsEar
28、lystepsoccurintheplastidsofrootandshootThesubstrateforMAX1canbemobileThesiteofactionofD27isunknownPerception and signalingThepearms4mutantisnotrescuedbyWTrootstocks;itisstrigolactone-insensitive.SimilarmutantshavebeenidentifiedinriceandArabidopsis.Beveridge,C.A.,Ross,J.J.,and Murfet,I.C.(1996).Branc
29、hing in pea(Action of genes Rms3 and Rms4).Plant Physiol.110:859-865;Beveridge,C.A.,Dun,E.A.,and Rameau,C.(2009).Pea has its tendrils in branching discoveries spanning a century from auxin to strigolactones.Plant Physiol.151:985-990.The Arabidopsis max2 mutant mutant is SL-insensitiveStirnberg,P.,va
30、n de Sande,K.,and Leyser,H.M.O.(2002).MAX1 and MAX2 control shoot lateral branching in Arabidopsis.Development 129:1131-1141;Stirnberg,P.,Furner,I.J.,and Ottoline Leyser,H.M.(2007).MAX2 participates in an SCF complex which acts locally at the node to suppress shoot branching.Plant J.50:80-94.WTmax3W
31、Tmax4WTmax1WTmax2WTmax4ScionRootMAX2 StrigolactonesInhibitionofshootbranchingCarotenoidCleavageproductMAX4(CCD8)MAX3(CCD7)MAX1(P450)WTrootdoesnotsuppressoutgrowthThe rice d3 mutant is SL-insensitiveD3 StrigolactonesInhibitionofshootbranchingCarotenoidCleavageproductD10(CCD8)D17(CCD7)ControlGR241cm1c
32、m(1M)WT d3 d10 d17 WT d3 d10 d17 ExogenousSLdoesnotsuppressoutgrowthUmehara,M.,Hanada,A.,Yoshida,S.,Akiyama,K.,Arite,T.,Takeda-Kamiya,N.,Magome,H.,Kamiya,Y.,Shirasu,K.,Yoneyama,K.,Kyozuka,J.,and Yamaguchi,S.(2008).Inhibition of shoot branching by new terpenoid plant hormones.Nature 455:195-200.The R
33、MS4/D3/MAX2 genes encode receptor-like F-box proteinsMAX2,D3andRMS4encodeF-boxproteinsrelatedtothoseinvolvedinauxinandjasmonateperceptionPossiblestrigolactonereceptor?AuxinreceptorJasmonateco-receptorJohnson,X.,Brcich,T.,Dun,E.A.,Goussot,M.,Haurogne,K.,Beveridge,C.A.,and Rameau,C.(2006).Branching ge
34、nes are conserved across species.Genes controlling a novel signal in pea are coregulated by other long-distance signals.Plant Physiol.142:1014-1026.d14 is another SL-insensitive mutant Arite,T.,Umehara,M.,Ishikawa,S.,Hanada,A.,Maekawa,M.,Yamaguchi,S.and Kyozuka,J.(2009).d14,a strigolactone-insensiti
35、ve mutant of rice,shows an accelerated outgrowth of tillers.Plant Cell Physiol.50:1416-1424.D14maybeinvolvedinactivationofthehormoneordownstreamsignalingAre the same signaling mechanisms used by AM,Striga and host?AMfungiRootparasitePutativereceptorStrigaislikelytousethesamereceptorasitscloselyrelat
36、edhost.WedontknowhowAMfungiperceiveSLs.Signaling summarySL-insensitiveplantshaverevealedgenesnecessaryforSLresponses,butmuchworkremainstobedonetoworkouthowSLsareperceivedandtheirsignaltransducedBranchinginAMfungiStimulationofgermination?Strigolactones and whole-plant processesStrigolactonesinwhole-p
37、lantprocesses:ShootbranchingMosscolonygrowthSymbiosisGerminationofStrigaandotherplantsTowardstheeliminationofStrigaparasitismStrigaHostRoot parasitesHow do strigolactones inhibit bud outgrowth?Goulet,C.and Klee,H.J.(2010).Climbing the branches of the strigolactones pathway one discovery at a time.Pl
38、ant Physiol.154:493-496.Axillary bud outgrowth is hormonally and environmentally responsiveMcSteen,P.(2009).Hormonal regulation of branching in grasses.Plant Physiol.149:46-55;Brewer,P.B.,Dun,E.A.,Ferguson,B.J.,Rameau,C.,and Beveridge,C.A.(2009).Strigolactone acts downstream of auxin to regulate bud
39、 outgrowth in pea and Arabidopsis.Plant Physiol.150:482-493.(Axilllameansarmpit)budAuxinandSLsinhibitoutgrowthCytokinins(CK)promoteitAuxin suppresses bud outgrowthThimann,K.V.,and Skoog,F.(1934).On the inhibition of bud development and other functions of growth substance in Vicia faba.Proc.Roy.Soc.B
40、114:317-339 with permission.DecapitateReplaceapexwithagarblock:withoutorwithauxin.AuxinsuppressesbudoutgrowthNoauxinAuxinBud LengthLocally elevated cytokinin induces bud outgrowthFrom Faiss,M.,Zalublov,J.,Strnad,M.,and Schmlling,T.(1997).Conditional transgenic expression of the ipt gene indicates a
41、 function for cytokinins in paracrine signaling in whole tobacco plants.Plant J.12:401-415.TIMEApplicationofcytokininAuxin downregulates cytokinin synthesisAuxinCytokininIPTIPTisacytokininbiosynthesisgeneAuxin upregulates strigolactone synthesisAuxinCCD7CCD8StrigolactonesCytokininIPTHayward,A.,Stirn
42、berg,P.,Beveridge,C.,and Leyser,O.(2009).Interactions between auxin and strigolactone in shoot branching control.Plant Physiol.151:400-412.Strigolactones dampen polar auxin transport(PAT)Reprinted from Bennett,T.,Sieberer,T.,Willett,B.,Booker,J.,Luschnig,C.,and Leyser,O.(2006).The Arabidopsis MAX pa
43、thway controls shoot branching by regulating auxin transport.Curr.Biol.16:553-563 with permission from Elsevier;Crawford,S.,Shinohara,N.,Sieberer,T.,Williamson,L.,George,G.,Hepworth,J.,Mller,D.,Domagalska,M.A.,and Leyser,O.(2010).Strigolactones enhance competition between shoot branches by dampening
44、 auxin transport.Development 137:2905-2913 reproduced with permission.SLreducesabundanceofPIN1auxintransporterSL-deficient plants showincreasedpolarauxintransportTransportedauxinSLs effects on branching may be mediated by effects on PATReprinted from Bennett,T.,Sieberer,T.,Willett,B.,Booker,J.,Lusch
45、nig,C.,and Leyser,O.(2006).The Arabidopsis MAX pathway controls shoot branching by regulating auxin transport.Curr.Biol.16:553-563 with permission from Elsevier;Excessivebranchinginthemax3mutantisreversedinamax3/pin1doublemutantModel:Auxin flow in main stem limits ability of bud to establish auxin f
46、lowPrusinkiewicz,P.,Crawford,S.,Smith,R.S.,Ljung,K.,Bennett,T.,Ongaro,V.,and Leyser,O.(2009).Control of bud activation by an auxin transport switch.Proc.Natl.Acad.Sci.USA 106:17431-17436.SchematicrepresentationofacellBylimitingPIN1expression,SLsreduceauxintransportglobally,makingitmoredifficultforbu
47、dstoestablishauxinexportintostemBranchescantestablishauxinflowRemovalofauxinsourcefromapexpermitsauxintransportfrombranchThese interlocking networks provide for local and systemic responsesHigh bud outgrowthLow bud outgrowthForexample,theycontributetotheshootsresponsetophosphatelimitationHighauxinHi
48、ghSLLowCKLowauxinLowSLHighCKP+PPhosphate-starvedplantssuppressshootgrowthandenhancerootgrowthNutrient control of branchingPhosphorous deficiency limits plant growth in much of the worldImage courtesy CIMMYT;FAO(2008)40milliontonnesperyearofphosphatefertilizerismined,transported,appliedtofarmlands,an
49、dinmanycasesrun-offtocontaminatelakesandrivers-P-P-P-PStrigolactones suppress shoot branching in low phosphorousNo.ofoutgrowingtillers01200.20.40.6Tillering1sttiller2ndtiller3rdtillerepi-5DS(nggFW-1)P(M)60030012060301206+P PStrigolactonelevelStrigolactonesynthesisishighandshootbranchingissuppressedw
50、henphosphateavailabilityislowUmehara,M.,Hanada,A.,Magome,H.,Takeda-Kamiya,N.,and Yamaguchi,S.(2010).Contribution of strigolactones to the inhibition of tiller bud outgrowth under phosphate deficiency in rice.Plant Cell Physiol.51:1118-1126.In the SL-deficient d10 mutant,branch outgrowth is independe
