A Downstream Mediator in the Growth Repression Limb of the Jasmonate Pathway

Abstract

Wounding plant tissues initiates large-scale changes in transcription coupled to growth arrest, allowing resource diversion for defense. These processes are mediated in large part by the potent lipid regulator jasmonic acid (JA). Genes selected from a list of wound-inducible transcripts regulated by the jasmonate pathway were overexpressed in Arabidopsis thaliana, and the transgenic plants were then assayed for sensitivity to methyl jasmonate (MeJA). When grown in the presence of MeJA, the roots of plants overexpressing a gene of unknown function were longer than those of wild-type plants. When transcript levels for this gene, which we named JASMONATE-ASSOCIATED1 (JAS1), were reduced by RNA interference, the plants showed increased sensitivity to MeJA and growth was inhibited. These gain-and loss-of-function assays suggest that this gene acts as a repressor of JA-inhibited growth. An alternative transcript from the gene encoding a second protein isoform with a longer C terminus failed to repress jasmonate sensitivity. This identified a conserved C-terminal sequence in JAS1 and related genes, all of which also contain Zim motifs and many of which are jasmonate-regulated. Both forms of JAS1 were found to localize to the nucleus in transient expression assays. Physiological tests of growth responses after wounding were consistent with the fact that JAS1 is a repressor of JA-regulated growth retardation.

A bHLH-Type Transcription Factor, ABA-INDUCIBLE BHLH-TYPE TRANSCRIPTION FACTOR/JA-ASSOCIATED MYC2-LIKE1, Acts as a Repressor to Negatively Regulate Jasmonate Signaling inArabidopsis

“…Identification of JASMONATE ZIM-DOMAIN (JAZ) proteins as targets of the E3 ligase SCF COI1 also facilitated elucidation of the JA signaling pathway (Chini et al, 2007;Thines et al, 2007). In the absence of JA, the activity of transcription factors that regulate JA responses is repressed by binding of JAZ and a corepressor complex consisting of NOVEL INTERACTOR OF JAZ (NINJA) and TOPLESS (Chini et al, 2007;Thines et al, 2007;Yan et al, 2007;Pauwels et al, 2010). When the bioactive JA-Ile conjugate is produced in response to endogenous and exogenous stimuli, formation of a COI1-JAZ coreceptor complex is promoted by JA-Ile, and JAZ is polyubiquitinated by the E3 ligase SCF COI1 and is then degraded by the 26S proteasome pathway (Chini et al, 2007;Thines et al, 2007;Katsir et al, 2008;Fonseca et al, 2009;Sheard et al, 2010).…”

“…However, because downregulation of the expression of early JA-responsive genes initiates while the JA-Ile level remains high (Koo et al, 2009(Koo et al, , 2011, additional mechanisms may act to attenuate transcription. For example, stable JAZ proteins produced by alternative splicing desensitize JA responsiveness in cells containing high JA-Ile levels (Yan et al, 2007;Chung and Howe, 2009;Chung et al, 2010). Overexpression of an alternatively spliced form of JAZ10, which is resistant to COI1-mediated degradation, considerably suppressed JA responses.…”

“…Jasmonates (JAs) are lipid-derived hormones that regulate plant responses to stresses such as wounding and herbivore attack and also act in various developmental processes, including male fertility (Devoto and Turner, 2003;Wasternack, 2007;Balbi and Devoto, 2008). JA negatively regulates plant growth and is considered to modulate the distribution of energy to defense responses (Yan et al, 2007;Zhang and Turner, 2008;Yang et al, 2012). Therefore, sophisticated mechanisms to control JA biosynthesis and the JA response at an appropriate level are necessary for optimal plant growth and development.…”

“…Mutants for ALLENE OXIDE SYNTHASE (AOS) or 12-OXOPHYTODIENOIC ACID REDUCTASE3 (OPR3)/ DELAYED DEHISCENCE1 have defects in endogenous JA production and reduced growth inhibition in response to wounding (Sanders et al, 2000;Stintzi and Browse, 2000;Park et al, 2002;Yan et al, 2007;Zhang and Turner, 2008). Wounding or JA application induces the expression of genes encoding JA biosynthetic enzymes and thus is expected to further increase JA production.…”

Identification and characterization of the MYC2 gene in relation to leaf senescence response in hybrid poplar (Populus alba × P. glandulosa)

“…repressor와 결합한다 (Chini et al 2007;Thines et al 2007;Yan et al 2007;Pauwels et al 2010). 그 결과로 MYC2, MYC3, MYC4를 포함한 JA 반응에 필수적인 다양한 하부 전사인자들이 활성 화된다 (Cheng et al 2011;Fernández-Calvo et al 2011;Niu et al 2011).…”