Interaction between MYC2and ETHYLENE INSENSITIVE3 Modulates Antagonism between Jasmonate and Ethylene Signaling in Arabidopsis C W
Susheng Song,a Huang Huang,a Hua Gao,a Jiaojiao Wang,a Dewei Wu,a Xili Liu,b Shuhua Yang,c Qingzhe Zhai,d Chuanyou Li,d Tiancong Qi,a,1and Daoxin Xie a,1,2
a Tsinghua-Peking Center for Life Sciences,MOE Key Laboratory of Bioinformatics,School of Life Sciences,Tsinghua University, Beijing100084,China
b Department of Plant Pathology,China Agricultural University,Beijing100193,China
c College of Biological Sciences,China Agricultural University,Beijing100193,China
d Stat
e Key Laboratory o
f Plant Genomics,National Centre for Plant Gene Research,Institute of Genetics and Developmental Biology, Chinese Academy of Sciences,Beijing100101,China
Plants have evolved sophisticated mechanisms for integration of endogenous and exogenous signals to adapt to the changing environment.Both the phytohormones jasmonate(JA)and ethylene(ET)regulate plant growth,development,and defense.In addition to synergistic regulation of root hair development and resistance to necrotrophic fungi,JA and ET act antagonistically to regulate gene expression,apical hook curvature,and plant defense against insect attack.However,the molecular mechanism for such antagonism between JA and ET signaling remains unclear.Here,we demonstrate that interaction between the JA-activated transcription factor MYC2and the ET-stabilized transcription factor ETHYLENE-INSENSITIVE3(EIN3) modulates JA and ET signaling antagonism in Arabidopsis thaliana.MYC2interacts with EIN3to attenuate the transcriptional activity of EIN3and repress ET-enhanced apical hook curvature.Conversely,EIN3interacts with and represses MYC2to inhibit JA-induced expression of wound-responsive genes and herbivory-inducible genes and to attenuate JA-regulated plant defense against generalist herbivores.Coordinated regulation of plant responses in both antagonistic and synergistic manners would help plants adapt to?uctuating environments.
INTRODUCTION
Sessile plants have evolved sophisticated mechanisms for in-tegration of endogenous and exogenous signals to regulate their growth,development,and defense responses,which bene?ts their survival in the changing environment.Both ethylene(ET) and jasmonate(JA)are essential plant hormones that regulate various plant developmental processes and perse defense re-sponses(Kieber,1997;Bleecker and Kende,2000;Guo and Ecker,2004;Broekaert et al.,2006;Howe and Jander,2008; Browse,2009;Shan et al.,2012;Wasternack and Hause,2013). ET signal is perceived by its receptors ETHYLENE RESPONSE1 (ETR1),ETR2,ETHYLENE RESPONSE SENSOR1(ERS1),ERS2, and ETHYLENE INSENSITIVE4(EIN4)(Hua and Meyerowitz, 1998)to repress CONSTITUTIVE TRIPLE RESPONSE1(CTR1) (Kieber et al.,1993),which activates EIN2(Alonso et al.,1999;Ju et al.,2012;Qiao et al.,2012;Wen et al.,2012)and subsequently stabilizes EIN3and EIN3-LIKE1(EIL1)(Chao et al.,1997;Guo and Ecker,2003;Potuschak et al.,2003;Gagne et al.,2004)to me-diate various ET responses,including hypocotyl growth(Zhong et al.,2012),apical hook formation(Knight et al.,1910;An et al., 2012),root growth(Ortega-Martínez et al.,2007;R?zicka et al., 2007),?owering(Ogawara et al.,2003;Achard et al.,2007),fruit ripening(Burg and Burg,1962;Theologis et al.,1992),leaf se-nescence(Gepstein and Thimann,1981;Li et al.,2013),freezing tolerance(Shi et al.,2012),and resistance against pathogen in-fection(Alonso et al.,2003;Chen et al.,2009).
JA plays essential roles in the regulation of plant development and defense.Upon perception of JA signal(Fonseca et al.,2009; Yan et al.,2009;Sheard et al.,2010),the F-box protein CORO-NATINE INSENSITIVE1(COI1)(Xie et al.,1998;Yan et al.,2009) recruits the JASMONATE ZIM-DOMAIN(JAZ)proteins(Chini et al.,2007;Thines et al.,2007;Yan et al.,2007)for degradation, which leads to the release of various downstream factors,in-cluding MYC2/JASMONATE INSENSITIVE1(JIN1),MYC3,and MYC4(Cheng et al.,2011;Fernández-Calvo et al.,2011;Niu et al.,2011),as well as WD-repeat/bHLH/MYB complex(Qi et al., 2011),MYB21,MYB24,and MYB57(Mandaokar et al.,2006; Song et al.,2011)and the IIId bHLH factors(Nakata et al.,2013; Song et al.,2013b),which regulate perse JA-mediated func-tions.These functions include root growth(Dathe et al.,1981; Chen et al.,2011),apical hook formation(Turner et al.,2002),?owering(Robson et al.,2010),stamen development(McConn and Browse,1996;Song et al.,2011,2013a),leaf senescence
1These authors contributed equally to this work.
2Address correspondence to daoxinlab@1a639f5dccbff121dc36833b.
The author responsible for distribution of materials integral to the?ndings
presented in this article in accordance with the policy described in the
Instructions for Authors(1a639f5dccbff121dc36833b)is:Daoxin Xie(daoxinlab@
1a639f5dccbff121dc36833b).
C Some?gures in this article are displayed in color online but in black and
white in the print edition.
W Online version contains Web-only data.
1a639f5dccbff121dc36833b/cgi/doi/10.1105/tpc.113.120394
The Plant Cell,Vol.26:263–279,January2014,1a639f5dccbff121dc36833b?2014American Society of Plant Biologists.All rights reserved.
(Ueda and Kato,1980;Shan et al.,2011),secondary metabolism (De Geyter et al.,2012;Schweizer et al.,2013),drought responses (Seo et al.,2011),wounding responses(Mason and Mullet,1990; Acosta et al.,2013;Mousavi et al.,2013),and defense against pathogen infection(Thomma et al.,1998;Vijayan et al.,1998; Melotto et al.,2006;Rowe et al.,2010;Yang et al.,2012;Zheng et al.,2012)and insect attack(McConn et al.,1997;Hu et al., 2013a).
Previous studies showed that both JA and ET concomitantly and synergistically regulate plant defense against necrotrophic fungi(Penninckx et al.,1998;Thomma et al.,1998;Thomma et al., 1999)and root hair development(Zhu et al.,2006).It is so far reported that such JA-ET signaling synergy is mediated by de-repression of ET-stabilized EIN3and EIL1:JAZ proteins directly interact with and repress EIN3/EIL1,while JA induces JAZ degradation to derepress EIN3and EIL1(Zhu et al.,2011).JA-induced EIN3and EIL1activation(Zhu et al.,2011)and ET-induced EIN3and EIL1stabilization(Guo and Ecker,2003; Potuschak et al.,2003;Gagne et al.,2004)mediate JA and ET signaling synergy in the regulation of root hair development and resistance against necrotrophic fungal infection.
In addition to their synergistic regulation,JA and ET also act antagonistically in regulating expression of wound-responsive genes(Rojo et al.,1999;Lorenzo et al.,2004)and metabolite biosynthetic genes(Mikkelsen et al.,2003).JA represses apical hook formation(Turner et al.,2002)and positively regulates plant defense against insect attack(Fernández-Calvo et al.,2011; Schweizer et al.,2013),while ET functions oppositely(Guzmán and Ecker,1990;Mewis et al.,2005,2006;Bodenhausen and Reymond,2007).However,the molecular mechanism for such antagonism between JA and ET signaling remains unclear.In this study,we show that MYC2interacts with EIN3and EIL1to re-press the transcriptional activity of EIN3and EIL1in Arabidopsis thaliana and consequently to inhibit ET-regulated apical hook formation;similarly,we found that EIN3and EIL1interact with and repress MYC2,further attenuate JA-induced expression of wound-responsive genes and herbivory-inducible genes,and in-hibit plant defense against insect attack.This molecular,bio-chemical,and genetic evidence reveals that interactions of the JA-activated transcription factor MYC2with the ET-stabilized transcription factors(EIN3and EIL1)repress their respective transcriptional activities to modulate JA and ET signaling antag-onism,which provides insights into how plants integrate various phytohormone signals to coordinately regulate plant development, growth,and defense.
RESULTS
MYC2,MYC3,and MYC4Function Redundantly to Mediate JA-Inhibited Apical Hook Curvature
The formation of the apical hook helps cotyledons and meristem tissues protrude from the soil without being damaged.Previous studies showed that ET induces hook curvature(Guzmán and Ecker,1990),whereas JA antagonizes the ET pathway that functions in apical hook formation in etiolated Arabidopsis seed-lings(Turner et al.,2002).Consistent with previous observations (Turner et al.,2002),1-aminocyclopropane-1-carboxylic acid (ACC),the ET biosynthesis precursor,enhanced the apical hook curvature,while JA obviously suppressed the ET-enhanced hook curvature of the dark-grown Arabidopsis wild-type seedlings (Figure1A);the coi1-1mutant exhibited an exaggerated apical hook curvature(Figure1A).As expected,the mutants with ET overproduction(ethylene overproducer1[eto1-1])or constitutive ET responses(ctr1-1)exhibited constitutive exaggerated hook curvature,while the mutants de?cient in ET signaling(ein2-1and ein3-1eil1-3)displayed obvious reduction in hook curvature (Figure1A).We further found that the exaggerated hook cur-vature in eto1-1and ctr1-1was clearly inhibited by JA(Figure 1A),which indicates that JA functions downstream of ETO1and CTR1to repress ET-regulated hook curvature.
