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JASMONATES Pathogens and pests cause significant crop lossesImages courtesy Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org; Charles Averre, North Carolina State University, Bugwood.orgJasmonates and salicylates are hormones that participate in plant defense responsesMost plants are resistant to most pests, but a few organisms cause tremendous damage. 25% or more of potential harvests can be lost to insects and disease!European corn borer Ostrinia nubilalis in its host Zea maysPhytophthora capsici on cucumber (Cucumis sativus) Jasmonates induce defenses to insects and necrotrophic pathogensTo a first approximation, insects and necrotrophic pathogens （死体营养型病原体）trigger jasmonate production, and biotrophic pathogens （活体营养型病原体）trigger salicylate productionJasmonatesSalicylatesTranscriptional responsesJasmonates also contribute to developmental and growth controlsLi, L., Zhao, Y., McCaig, B.C., Wingerd, B.A., Wang, J., Whalon, M.E., Pichersky, E., and Howe, G.A. (2004). The tomato homolog of CORONATINE-INSENSITIVE1 is required for the maternal control of seed maturation, jasmonate-signaled defense responses, and glandular trichome development. Plant Cell 16: 126-143; Reprinted by permission from Macmillan Publishers Ltd. Thines, B., Katsir, L., Melotto, M., Niu, Y., Mandaokar, A., Liu, G., Nomura, K., He, S.Y., Howe, G.A., and Browse, J. (2007). JAZ repressor proteins are targets of the SCFCOI1 complex during jasmonate signalling. Nature 448: 661-665.Male and female reproductive developmentAlso cell cycle control, senescence, mutualistic interactions.Trichome formationJasmonates include jasmonic acid (JA) and derivativesJA-IleOH(3R,7S)-jasmonic acida.k.a.(+)-7-iso-jasmonic acidJasmonic acid (JA)JA-Isoleucine(JA-Ile)OCH3Methyl jasmonate(MeJA)Yan, J., Zhang, C., Gu, M., Bai, Z., Zhang, W., Qi, T., Cheng, Z., Peng, W., Luo, H., Nan, F., Wang, Z., and Xie, D. (2009). The Arabidopsis CORONATINE INSENSITIVE1 protein Is a jasmonate receptor. Plant Cell 21: 2220-2236.Methyl jasmonate was purified from Jasminum grandiflorium（素馨属） in 1962Demole, E. Lederer, E., and Mercier, D. (1962) Isolement et dtermination de la structure du jasmonate de mthyle, constituant odorant charactristique de lssence de jasmin. Helv. Chim. Acta 45: 675 -685; Gundlach, H., Mller, M.J., Kutchan, T.M., and Zenk, M.H. (1992). Jasmonic acid is a signal transducer in elicitor-induced plant cell cultures. Proc. Natl. Acad. Sci. 89: 2389-2393.Like other esters酯, methyl jasmonate smells good it is the dominant scent from jasmine flowers“ “Jasmonate de mthyle” ”OCH2COOCH3Wounding, pathogens and herbivores trigger rapid accumulation of jasmonates JAMeJAUntreated controlJasmonate synthesis occurs in the plastid, peroxisome and cytoplasmLOXAOSAOCOPDAOPDAOPR3-oxidationJAMeJAJA-IleplastidperoxisomeLipase-linolenic acidJasmonic acid can be conjugated to amino acids by JAR1OHJAJA-IleisoleucineNH2JAR1Active formJAR1 is an amino acid conjugaseThe active form of the hormone is JA-isoleucine (JA-Ile)JAR1 was identified as the jasmonate-insensitive mutant jar1Staswick, P.E., Su, W., and Howell, S.H. (1992). Methyl jasmonate inhibition of root growth and induction of a leaf protein are decreased in an Arabidopsis thaliana mutant. Proc. Natl. Acad. Sci. USA 89: 6837-6840; Staswick, P.E., and Tiryaki, I. (2004). The oxylipin signal jasmonic acid is activated by an enzyme that conjugates it to isoleucine in Arabidopsis. Plant Cell 16: 2117-2127.Arabidopsis jar1 mutants produce jasmonic acid but cannot make JA-IleRoot growth on MeJA is less inhibited in jar1 mutants.jar1WTPerception and signalingJA-Ile binding by the COI1-JAZ coreceptorUbiquitination and degradation of JAZTranscriptional activation by MYC2 and othersGene expressionSCFCOI1JZJA-IleMYC2BDADJAZJZMYC2BDADCoronatine（冠菌素） is a bacterial compound and powerful jasmonate mimicReprinted from Weiler, E.W., Kutchan, T.M., Gorba, T., Brodschelm, W., Niesel, U., and Bublitz, F. (1994). The Pseudomonas phytotoxin coronatine mimics octadecanoid signalling molecules of higher plants. FEBS Letters 345: 9-13 with permission from Elsevier. Yan, J., Zhang, C., Gu, M., Bai, Z., Zhang, W., Qi, T., Cheng, Z., Peng, W., Luo, H., Nan, F., Wang, Z., and Xie, D. (2009). The Arabidopsis CORONATINE INSENSITIVE1 protein Is a jasmonate receptor. Plant Cell 21: 2220-2236.MeJACORControlMeJA or coronatine (COR) induce defense compounds in cultured cells of California poppy罂粟Coronatine is a toxin produced by some pathogenic bacteria that mimics jasmonate action and structurally resembles JA-Ile(3R,7S)-JA-IleCoronatineThe Arabidopsis mutant coi1 is insensitive to coronatine and MeJAFeys, B., Benedetti, C.E., Penfold, C.N., and Turner, J.G. (1994). Arabidopsis mutants selected for resistance to the phytotoxin coronatine are male sterile, insensitive to methyl jasmonate, and resistant to a bacterial pathogen. Plant Cell 6: 751-759.coi1coi1WTWTMeJACORWTcoi1ControlCOI1 is an F-box protein very similar to the auxin receptor TIR1Reprinted from Katsir, L., Chung, H.S., Koo, A.J.K., and Howe, G.A. (2008). Jasmonate signaling: a conserved mechanism of hormone sensing. Curr. Opin. Plant Biol. 11: 428-435, with permission from Elsevier. This similarity suggests a mode of action! The jasmonate receptor consists of COI1 and JAZ co-receptorsReprinted by permission from Macmillan Publishers Ltd. Nature: Sheard, L.B., Tan, X., Mao, H., Withers, J., Ben-Nissan, G., Hinds, T.R., Kobayashi, Y., Hsu, F.-F., Sharon, M., Browse, J., He, S.Y., Rizo, J., Howe, G.A., and Zheng, N. (2010) Jasmonate perception by inositol-phosphate-potentiated COI1-JAZ co-receptor. Nature 468: 400-405 copyright 2010. COI1JZJA-IleThe COI1-JAZ co-receptor has 100 fold greater affinity for the ligand than either COI1 or JAZ aloneJasmonate (like auxin) signaling requires repressor degradationRepressorTranscriptional activatorJAZMYC2Aux/IAAARFF-box proteinTIR1COI1hormoneRepressorTranscriptional activatorAuxinJA-IleJAZMYC2Aux/IAAARF+ hormoneIn the absence of hormone, a repressor interferes with a transcriptional activator. The hormone promotes an interaction between the repressor and an F-box protein, leading to repressor degradation and transcriptional activation The jasmonate signaling pathwayBDADSCFCOI1JA-IleTPLJAZJZNINJAMYC2BDADEAR1.JA-Ile binds to SCFCOI1 and JAZ protein2. JAZ ubiquitinated and degraded by 26S proteasome3. Degradation of repressor permits transcriptional activation by MYC2 and other transcription factorsMYC2JA-IleJamonate signaling contributes to defenses against herbivoryWT Mutant without JAWhen exposed to hungry fly larvae幼虫, plants unable to produce JA have low rates of survivalMcConn, M., Creelman, R.A., Bell, E., Mullet, J.E., and Browse, J. (1997). Jasmonate is essential for insect defense in Arabidopsis. Proc. Natl. Acad. Sci. USA 94: 5473-5477.Jasmonates accumulate extremely quickly after woundingGlauser, G., Dubugnon, L., Mousavi, S.A.R., Rudaz, S., Wolfender, J.-L., and Farmer, E.E. (2009). Velocity estimates for signal propagation leading to systemic jasmonic acid accumulation in wounded Arabidopsis. J. Biol. Chem. 284: 34506-34513.Unwounded plantW (wounded) part of leaf U (unwounded) part of leafWhen a leaf is crushed with forceps, the level of JA in the wounded and unwounded part of the leaf increases within a minute Anti-herbivory genes are induced by jasmonate treatmentFarmer, E.E., Johnson, R.R., and Ryan, C.A. (1992). Regulation of expression of proteinase inhibitor genes by methyl jasmonate and jasmonic acid. Plant Physiol. 98: 995-1002.24410362Proteinase inhibitor (PI) gene expression is induced by Wounding or Methyl JasmonateMeJA vapor promotes PI accumulation in exposed leaves but also unexposed leaves of the same plant No MJ controlWhat is the signal that moves systemically?Jasmonate mediates defenses against necrotrophic pathogensPhoto credit Gary LoakeArabidopsis plants infected with Botrytis cinerea 灰葡萄孢菌 灰霉病JA-insensitive plants are more susceptible to pathogensThomma, B.P.H.J., Eggermont, K., Penninckx, I.A.M.A., Mauch-Mani, B., Vogelsang, R., Cammue, B.P.A., and Broekaert, W.F. (1998). Separate jasmonate-dependent and salicylate-dependent defense-response pathways in Arabidopsis are essential for resistance to distinct microbial pathogens. Proc. Natl. Acad. Sci. USA 95: 15107-15111 copyright 1998 National Academy of Sciences USA. Alternaria brassicicolaBotyrtis cinereaJA-induces plant defenses against pathogensPhoto credit: USDAPeanut kernel infected by a soil fungus (Aspergillus niger). Yellow-colored phytoalexin is locally produced by the kernel谷粒 tissues (arrow). JA-mediated responses to pathogens include production of phytoalexins植物抗毒素, and antimicrobial peptides or proteinsJA seems to play a role in establishing mutualistic interactions互惠的相互作用Reprinted from Hause, B., and Schaarschmidt, S. (2009). The role of jasmonates in mutualistic symbioses between plants and soil-born microorganisms. Phytochemistry 70: 1589-1599 with permission from Elsevier. Arbuscular mycorrhizaLegume-rhizobia symbiosis丛枝菌根：对草本和灌木吸收养分非常重要。菌根：是自然界中一种普遍的植物共生现象， 它是土壤中的菌根真菌菌丝与高等植物营养根系形成的一种联合体。共生真菌从植物体内获取必要的碳水化合物及其他营养物质， 而植物也从真菌那里得到所需的营养及水分等， 从而达到一种互利互助、互通有无的高度统一。它既具有一般植物根系的特征， 又具有专性真菌的特性。 豆科植物的根瘤菌 Ongoing questionsJAMeJAJA-IlevWhat signals trigger JA synthesis and signaling pathways? vHow does the plant discriminate between threats? vWhat is the systemic signal?vWhat do the different JAZ proteins do?vHow is the diversity of JA responses controlled in specific organs and cell types?COI1JZJA-IleBrassinosteroidsBrassinolide (BL)Brassinosteroids (BRs) are a family of 50 structurally related compounds that contribute to:GrowthCell division, elongation, and differentiationDefense against pathogensStress toleranceReproductive developmentCastasterone (CS)栗甾酮 ,被认为是油菜素内酯生物合成的前体 Brassinolide and castasterone are steroids like some animal hormones InsectPlantMammalBishop, G.J., and Koncz, C. (2002). Brassinosteroids and plant steroid hormone signaling. Plant Cell 14: S97-110.栗木甾酮 雌(甾)二醇睾丸激素甾酮蜕皮素Characterization of det2 and cpd showed that BRs are essentialFrom Li, J. et al. (1996) A role for brassinosteroids in light-dependent development of Arabidopsis. Science 272: 398401; reprinted with permission from AAAS. Reprinted from Szekeres, M. et al. (1996) Brassinosteroids rescue the deficiency of CYP90, a cytochrome P450, controlling cell elongation and de-etiolation in Arabidopsis. Cell 85: 171182 with permission from Elsevier. WTdet2det2 + BLWTdet2det2 + BLWTcpdIn 1996, two Arabidopsis mutants, de-etiolated2 (det2) and constitutive photomorphogenesis and dwarfism (cpd) were shown to be BR-deficient. Biosynthesis and homeostasisBR-deficient plants are severely dwarfedA likely pathway for BR synthesisReprinted from Ohnishi, T., Yokota, T., and Mizutani, M. (2009). Insights into the function and evolution of P450s in plant steroid metabolism. Phytochemistry 70: 1918-1929 with permission from Elsevier.CampesterolCastasteroneBrassinolideDET2DWF4DWF1 / LKB / BRD2DWARF(tomato)CampesterolDWF4 encodes a CYP C22-oxidase dwf4 wild-typeDWF4 encodes cytochrome P450 CYP90B1, a C22-oxidase. Loss-of-function mutants are dwarfedCYP90B1 catalyzes a flux-determining stepDWF4Four dwarf4 mutantsAzpiroz, R., Wu, Y., LoCascio, J.C., and Feldmann, K.A. (1998). An Arabidopsis brassinosteroid-dependent mutant Is blocked in cell elongation. Plant Cell 10: 219-230; Choe, S., Dilkes, B.P., Fujioka, S., Takatsuto, S., Sakurai, A., and Feldmann, K.A. (1998). The DWF4 gene of Arabidopsis encodes a cytochrome P450 that mediates multiple 22-hydroxylation steps in brassinosteroid biosynthesis. Plant Cell 10: 231-244.BRI1 encodes the main BR receptor; bri1 mutants are BR-insensitiveClouse, S.D., Langford, M., and McMorris, T.C. (1996). A brassinosteroid-insensitive mutant in Arabidopsis thaliana exhibits multiple defects in growth and development. Plant Physiol. 111: 671-678.bri1Wild-typeWild-typebri1bri1In wild-type plants, root growth is inhibited by elevated BR levelsThe Arabidopsis bri1 mutant is very small (below) and insensitive to exogenous BR1 cm1 cmThe BRI1 receptor is a plasma-membrane localized LRR-RLKBRI1Leucine-rich repeat (LRR)Trans-membrane domainKinase DomainReprinted from Li, J., and Chory, J. (1997). A putative leucine-rich repeat receptor kinase involved in brassinosteroid signal transduction. Cell 90: 929-938, with permission from Elsevier; Bishop, G.J., and Koncz, C. (2002). Brassinosteroids and plant steroid hormone signaling. Plant Cell 14: S97-110.BRI1 is a Leucine-rich repeat receptor like kinase (LRR-RK)bri1The BRI1 gene was identified through map-based cloning BRs bind to BRI1s extracellular leucine-rich repeat domainReprinted by permission from Macmillan Publishers Ltd: She, J., Han, Z., Kim, T.-W., Wang, J., Cheng, W., Chang, J., Shi, S, Wang, J. ,Yang, M., Wang, Z.-Y., and Chai, J. (2011). Structural insight into brassinosteroid perception by BRI1. Nature 474: 472-477. Hothorn, M., Belkhadir, Y., Dreux, M., Dabi, T., Noel, J.P., Wilson, I.A., and Chory, J. (2011). Structural basis of steroid hormone perception by the receptor kinase BRI1. Nature 474: 467-471.70 The LRR domain forms a helical solenoidSide viewTop viewBRs bind through an induced fit mechanismBinding siteBRI1 signaling is negatively regulated by BKI1Wang, X., and Chory, J. (2006) Brassinosteroids regulate dissociation of BKI1, a negative regulator of BRI1 signaling, from the plasma membrane. Science 313:1118-1122. Reprinted with permission from AAASWild-type ArabidopsisBKI1 overexpressionLow BRReceptor(BRI1)Inhibitor(BKI1)BKI1 was identified through a search for proteins that physically interact with BRI1 BRI1 signaling requires activation by a coreceptor BAK1BAK1 was identified by an activation screen a screen for plants that partially reverse the dwarf bri1-5 phenotype when overexpressedReprinted from Li, J., Wen, J., Lease, K.A., Doke, J.T., Tax, F.E., and Walker, J.C. (2002). BAK1, an Arabidopsis LRR Receptor-like protein kinase, interacts with BRI1 and modulates brassinosteroid signaling. Cell 110: 213-222 with permission from Elsevier.BAK1High BRThe BRI1/BAK1 complex auto- and transphosphorylates,fully activating BRI1 kinase activityBRI1 and BAK1 interact through a “double lock mechanism”Reprinted by permission from Jaillais, Y., Belkhadir, Y., Balsemo-Pires, E., Dangl, J.L. and Chory, J. (2011). Extracellular leucine-rich repeats as a platform for receptor/coreceptor complex formation. Proc. Natl. Acad. Sci. USA 108: 8503-8507.Unoccupied BRI1: Extracellular and cytoplasmic domains prevent BAK1 interactionOccupied BRI1: Phosphorylation of BKI1 causes it to dissociate, and interactions in both domains of BRI1 promote association with coreceptor BAK1Summary BR receptor actionReceptor(BRI1)Low BRInhibitor(BKI1)BAK1High BRLow BR levels receptor inactive and inhibited by BKI1High BR levels BRI1 autophosphorylates, BKI1 dissociates, BAK1 binds and enhances BR1 activityPPPPDownstream of the receptor, BR activates transcription factorsBAK1BZR1 and BZR2/BES1 turn on growth promoting genes and off biosynthesis genesBZR1CPDDWF4BR6OXHigh BRPPPPGenes promoting growth and cell elongationBZR2BES1BL induces BZR2/BES1 to move into the nucleus. BZR1 and BES1/BZR2 are regulated by phosphorylation stateReceptor(BRI1)Low BRInhibitor(BKI1)BAK1High BRPPPPBIN2BSU1PBSKsPPPBIN2P26S proteasomeLow BR: BZR1 and BZR2 are phosphorylated and inactivated by the protein kinase BIN2High BR: BZR1 and BZR2 are dephosphorylated and active and able to interact with DNA because BIN2 is inactive, dephosphorylated by BSU1 and other protein phosphatasesBR signaling - summary BR is perceived by the membrane-bound BIN1 receptor In the absence of BR, BRI1 is complexed with the inhibitor BKI1, but BR-binding causes BRI1 to bind BAK1, enhancing BRI1s activity The BRI1/BAK1 complex phosphorylates and activates BSU1, a protein phosphatase, which dephosphorylates BIN2, inactivating it Dephosphorylated BZR1 and BZR2 move into the nucleus and activate or repress BR-regulated genesBRs in whole-plant processes BRs promote cell division and cell elongation BRs are involved in development of vascular and other tissues BRs can enhance tolerance to stress and pathogens BRs are involved in responses to lightReprinted from Yang, C.-J., Zhang, C., Lu, Y.-N., Jin, J.-Q. and Wang, X.-L. (2011). The mechanisms of brassinosteroids action: From signal transduction to plant development. Mol. Plant. 4: 588-600 by permission of Oxford University PressBrassinosteroids promote cell elongationWang, T.W., Cosgrove, D.J., and Arteca, R.N. (1993). Brassinosteroid stimulation of hypocotyl elongation and wall relaxation in pakchoi (Brassica chinensis cv Lei-Choi). Plant Physiol. 101: 965-968. Yamamuro, C., Ihara, Y., Wu, X., Noguchi, T., Fujioka, S., Takatsuto, S., Ashikari, M., Kitano, H., and Matsuoka, M. (2000). Loss of function of a rice brassinosteroid insensitive1 homolog prevents internode elongation and bending of the lamina Joint. Plant Cell 12: 1591-1606.Wild-typeReceptor mutantCell elongation and microtubule organization are abnormal in a rice BR receptor mutant.BR application promotes hypocotyl elongation.Brassinosteroids are necessary for stamen and pollen developmentFilament elongationPollen developmentPollen tube elongationImage credits: Safro; Graham Matthews; Szumlanski, A.L., and Nielsen, E. (2009). The Rab GTPase RabA4d regulates pollen tube tip growth in Arabidopsis thaliana. Plant Cell 21: 526-544.BRs contribute to fruit ripeningEndogenous BR levels rise when berries ripenExogenous BR application hastens ripening. Application of a BR-synthesis inhibitor slows ripening. Symons, G.M., Davies, C., Shavrukov, Y., Dry, I.B., Reid, J.B., and Thomas, M.R. (2006). Grapes on steroids. Brassinosteroids are involved in grape berry ripening. Plant Physiology 140: 150-158.BRs contribute to stress toleranceAntioxidantsSTRESSBRsToleranceHeavy metals (OUT)Heavy metals (IN)UptakeDetoxBRsCELLULAR DAMAGEBRs contribute to the production of antioxidants, which protect cells from damage. BRs may also interfere with the uptake of heavy metals and promote their detoxification through antioxidant production and other means.BRs contribute to light-regulated developmentWTdet2det2 + BLThe original BR synthesis mutants were identified by their de-etiolated growth pattern in the darkLIGHTBRsLight responsive genes and growth patternsBRs interfere with light responses, and light interferes with BR synthesis and promotes its inactivationBrassinosteroids SummaryPPPPSYNTHESISSome transcriptional targets have been identifiedBRs are synthesized in young, growing tissuesBRs are perceived via the extracellular domain of a BRI1BRI1 activity is controlled positively and negatively by binding partnersDownstream signaling is mediated by protein kinases and phosphatasesTRANSCRIPTIONAL AND OTHER RESPONSESBrassinosteroids Summary and ongoing researchWhat non-transcriptional responses do BRs mediate? PPPPSYNTHESISWhat determines when and where BRs are synthesized ?How are BRs exported to interact with the extracellular receptor domain? How are other signals integrated into BR responses? How does BRI1 interact with its partners?TRANSCRIPTIONAL AND OTHER RESPONSESSalicylates plant hormones and painkillersSalicylic AcidAcetylsalicylic AcidASPIRINPhoto credits: Geaugagrrl; Sten PorseNamed for white willow Salix albaNamed for Spiraea, the former name for meadowsweet（绣线菊，珍珠花）How do salicylates work in plants? SAs effects in plants and animals are unrelated Expression of pathogen-induced genesIncreased synthesis of SASignal (e.g. Pathogen, UV light, developmental cues)In plants SAs main effect is to alter patterns of gene expressionDEFENSEDevelopmental responsesStress responsesHistory of salicylate researchNational Library of Medicine; Raskin, I. (1992). Salicylate, a new plant hormone. Plant Physiol. 99: 799-803.Hippocrates wrote about the use of willow to relieve pain 2400 years agoIn 1979 White showed
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