JAZ8 Lacks a Canonical Degron and Has an EAR Motif That Mediates Transcriptional Repression of Jasmonate Responses in Arabidopsis
JAZ8 Lacks a Canonical Degron and Has an EAR Motif That Mediates Transcriptional Repression of Jasmonate Responses in Arabidopsis
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DOI：
10.1105/tpc.111.093005
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发表时间：
2012-02-01
期刊：
影响因子：
11.6
通讯作者：
Howe, Gregg A.
中科院分区：
文献类型：
--
作者：
Shyu, Christine;Figueroa, Pablo;Howe, Gregg A.
脂质衍生激素茉莉酸-L-Ile（JA-Ile）通过稳定JASMONATE ZIM结构域（JAZ）阻遏物与F盒蛋白CORONATINE INSENSITIVE 1（COI 1）的相互作用，引发基因表达的大规模变化，这导致JAZ通过泛素-蛋白酶体途径降解。最近的结构研究表明，JAZ 1降解信号（降解决定子）包括一个短的保守LPIAR基序，密封JA-Ile在其结合口袋中的COI 1-JAZ接口。在这里，我们表明，拟南芥JAZ 8缺乏这个基序，因此是无法与COI 1强烈的JA-Ile的存在下。因此，JAZ 8对茉莉酸（JA）介导的降解是稳定的，并且当在拟南芥中异位表达时，抑制JA调节的生长和防御反应。这些发现表明，降解决定子高变区的序列变异影响JAZ稳定性和JA调节的生理反应。我们还表明，JAZ 8介导的抑制依赖于一个LxLxL-型ERF相关的两亲性抑制基序在JAZ 8 N末端，结合辅阻遏物TOPLESS和抑制转录激活。JAZ 8介导的抑制不需要ZIM结构域，而在其他JAZ蛋白中，ZIM结构域通过包含EAR基序的衔接蛋白NINJA招募TOPLESS。这些发现表明，JAZ蛋白亚组中的阻遏结构域通过直接募集辅阻遏物到同源转录因子来抑制基因表达。
The lipid-derived hormone jasmonoyl-L-Ile (JA-Ile) initiates large-scale changes in gene expression by stabilizing the interaction of JASMONATE ZIM domain (JAZ) repressors with the F-box protein CORONATINE INSENSITIVE1 (COI1), which results in JAZ degradation by the ubiquitin-proteasome pathway. Recent structural studies show that the JAZ1 degradation signal (degron) includes a short conserved LPIAR motif that seals JA-Ile in its binding pocket at the COI1-JAZ interface. Here, we show that Arabidopsis thaliana JAZ8 lacks this motif and thus is unable to associate strongly with COI1 in the presence of JA-Ile. As a consequence, JAZ8 is stabilized against jasmonate (JA)-mediated degradation and, when ectopically expressed in Arabidopsis, represses JA-regulated growth and defense responses. These findings indicate that sequence variation in a hypervariable region of the degron affects JAZ stability and JA-regulated physiological responses. We also show that JAZ8-mediated repression depends on an LxLxL-type EAR (for ERF-associated amphiphilic repression) motif at the JAZ8 N terminus that binds the corepressor TOPLESS and represses transcriptional activation. JAZ8-mediated repression does not require the ZIM domain, which, in other JAZ proteins, recruits TOPLESS through the EAR motif-containing adaptor protein NINJA. These findings show that EAR repression domains in a subgroup of JAZ proteins repress gene expression through direct recruitment of corepressors to cognate transcription factors.