ETHYLENE INSENSITIVE3 and ETHYLENE INSENSITIVE3-LIKE1 Repress SALICYLIC ACID INDUCTION DEFICIENT2 Expression to Negatively Regulate Plant Innate Immunity in Arabidopsis    

Abstract

Pathogen/microbe-associated molecular patterns (PAMPs/MAMPs) trigger plant immunity that forms the first line inducible defenses in plants. The regulatory mechanism of MAMP-triggered immunity, however, is poorly understood. Here, we show that Arabidopsis thaliana transcription factors ETHYLENE INSENSITIVE3 (EIN3) and ETHYLENE INSENSITIVE3-LIKE1 (EIL1), previously known to mediate ethylene signaling, also negatively regulate PAMP-triggered immunity. Plants lacking EIN3 and EIL1 display enhanced PAMP defenses and heightened resistance to Pseudomonas syringae bacteria. Conversely, plants overaccumulating EIN3 are compromised in PAMP defenses and exhibit enhanced disease susceptibility to Pseudomonas syringae. Microarray analysis revealed that EIN3 and EIL1 negatively control PAMP response genes. Further analyses indicated that SALICYLIC ACID INDUCTION DEFICIENT2 (SID2), which encodes isochorismate synthase required for pathogen-induced biosynthesis of salicylic acid (SA), is a key target of EIN3 and EIL1. Consistent with this, the ein3-1 eil1-1 double mutant constitutively accumulates SA in the absence of pathogen attack, and a mutation in SID2 restores normal susceptibility in the ein3 eil1 double mutant. EIN3 can specifically bind SID2 promoter sequence in vitro and in vivo. Taken together, our data provide evidence that EIN3/EIL1 directly target SID2 to downregulate PAMP defenses.

Direct transcriptional control of the Arabidopsis immune receptor FLS2 by the ethylene-dependent transcription factors EIN3 and EIL1

“…On flg22 binding, FLS2 activates MPK6 that, in turn, phosphorylates ACS2/6 and further leads to EIN3 stabilization, resulting in increased ethylene production and signaling. Congruently, flg22 perception leads to EIN3 accumulation (31). This model may explain the longestablished observation that PAMP perception triggers increased ethylene biosynthesis (14)(15)(16).…”

“…Previous reports show the role of ethylene in disease symptom development and susceptibility to bacteria conflict (29,30). Recently, EIN3 and EIL1 were shown to repress biosynthesis of the immune hormone salicylic acid (SA) (31). Consequently, ein2-1 and ein3-1 eil1-1 plants exhibited enhanced resistance to the pathogenic bacterium P. syringae pv.…”

“…Consequently, ein2-1 and ein3-1 eil1-1 plants exhibited enhanced resistance to the pathogenic bacterium P. syringae pv. tomato (Pto) DC3000, suggesting that they overaccumulate (SA) (31). However, a previous study showed that ethylene-insensitive mutant plants were more tolerant to bacteria (reduced symptoms), but no decrease in bacterial numbers could be observed (32, 33); we observed that Pto DC3000 infiltrated at low dose (10 5 cfu/mL −1 ) multiplied to lower levels in ein2-5 and ein2-1 leaves than in wild-type leaves (Fig.…”

Interaction between MYC2 and ETHYLENE INSENSITIVE3 Modulates Antagonism between Jasmonate and Ethylene Signaling inArabidopsis

“…Both ethylene (ET) and jasmonate (JA) are essential plant hormones that regulate various plant developmental processes and diverse defense responses (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 EIN3 and EIN3-LIKE1 (EIL1) (Chao et al, 1997;Guo and Ecker, 2003;Potuschak et al, 2003;Gagne et al, 2004) to mediate 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;Růzicka et al, 2007), flowering (Ogawara et al, 2003;Achard et al, 2007), fruit ripening (Burg and Burg, 1962;Theologis et al, 1992), leaf senescence (Gepstein and Thimann, 1981;Li et al, 2013), freezing tolerance , and resistance against pathogen infection (Alonso et al, 2003;Chen et al, 2009).…”

Two redundant receptor-like cytoplasmic kinases function downstream of pattern recognition receptors to regulate activation of SA biosynthesis in Arabidopsis

“…The induction of ICS1 expression is mainly controlled by the transcription factors SARD1 and CBP60g (Wang et al, 2009(Wang et al, , 2011. Some other transcriptional regulators, including WRKY28, NTM1-like9, CCA1 hiking expedition, Nonexpressor of Pathogenesis-Related genes1, Ethylene Insensitive3, and Ethylene Insensitive3-Like1, also influence the expression of ICS1 (Wildermuth et al, 2001;Chen et al, 2009;van Verk et al, 2011;Zheng et al, 2015). Recently, SARD1 and CBP60g were also reported to function as master regulators of plant immunity that regulate the expression of a large number of plant defense regulators in addition to ICS1 (Sun et al, 2015).…”