EIN3 and ORE1 Accelerate Degreening during Ethylene-Mediated Leaf Senescence by Directly Activating Chlorophyll Catabolic Genes in Arabidopsis.
EIN3 and ORE1 Accelerate Degreening during Ethylene-Mediated Leaf Senescence by Directly Activating Chlorophyll Catabolic Genes in Arabidopsis.
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EIN3 和 ORE1 通过直接激活拟南芥叶绿素分解代谢基因加速乙烯介导的叶片衰老过程
DOI：
10.1371/journal.pgen.1005399
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发表时间：
2015-07
期刊：
影响因子：
4.5
通讯作者：
Zhou X
中科院分区：
文献类型：
--
作者：
Qiu K;Li Z;Yang Z;Chen J;Wu S;Zhu X;Gao S;Gao J;Ren G;Kuai B;Zhou X
由叶绿素降解引起的萎黄是叶片衰老的最明显的症状。叶绿素降解可由内源和环境因素引起，乙烯是主要的诱导因子之一。乙烯不敏感3（EIN 3）是乙烯信号转导途径中的关键转录因子。先前报道，EIN 3、miR 164和NAC（NAM、ATAF和CUC）转录因子ORE 1/NAC 2构成介导叶片衰老的调控网络。然而，这个网络如何在分子水平上调节叶绿素降解尚未阐明。在这里，我们报告了一个前馈调节叶绿素降解，涉及EIN 3，ORE 1，和叶绿素分解代谢基因（CCGs）。基因表达分析表明，在ein 3 eil 1双突变体中，乙烯对NYE 1、NYC 1和PAO三个主要CCG的诱导作用在很大程度上受到抑制。双荧光素酶分析表明，EIN 3能显著增强NYE 1、NYC 1和PAO在拟南芥原生质体中的启动子活性。电泳迁移率变动分析（EMSA）表明EIN 3可与NYE 1、NYC 1和PAO启动子直接结合。这些结果表明，EIN 3作为一个积极的调节CCG表达乙烯介导的叶绿素降解。有趣的是，ORE 1是EIN 3的下游靶点，它也可以通过直接结合到它们的启动子上来激活NYE 1、NYC 1和PAO的表达。此外，EIN 3和ORE 1以相加的方式促进NYE 1和NYC 1的转录。这些结果表明ORE 1也参与了CCG转录的直接调控。此外，ORE 1激活了一个主要的乙烯生物合成基因ACS 2的表达，随后促进了乙烯的产生。总的来说，我们的工作表明，EIN 3，ORE 1和CCGs构成了一个连贯的前馈回路，参与了拟南芥叶片衰老过程中乙烯介导的叶绿素降解的鲁棒调节。
Degreening, caused by chlorophyll degradation, is the most obvious symptom of senescing leaves. Chlorophyll degradation can be triggered by endogenous and environmental cues, and ethylene is one of the major inducers. ETHYLENE INSENSITIVE3 (EIN3) is a key transcription factor in the ethylene signaling pathway. It was previously reported that EIN3, miR164, and a NAC (NAM, ATAF, and CUC) transcription factor ORE1/NAC2 constitute a regulatory network mediating leaf senescence. However, how this network regulates chlorophyll degradation at molecular level is not yet elucidated. Here we report a feed-forward regulation of chlorophyll degradation that involves EIN3, ORE1, and chlorophyll catabolic genes (CCGs). Gene expression analysis showed that the induction of three major CCGs, NYE1, NYC1 and PAO, by ethylene was largely repressed in ein3 eil1 double mutant. Dual-luciferase assay revealed that EIN3 significantly enhanced the promoter activity of NYE1, NYC1 and PAO in Arabidopsis protoplasts. Furthermore, Electrophoretic mobility shift assay (EMSA) indicated that EIN3 could directly bind to NYE1, NYC1 and PAO promoters. These results reveal that EIN3 functions as a positive regulator of CCG expression during ethylene-mediated chlorophyll degradation. Interestingly, ORE1, a senescence regulator which is a downstream target of EIN3, could also activate the expression of NYE1, NYC1 and PAO by directly binding to their promoters in EMSA and chromatin immunoprecipitation (ChIP) assays. In addition, EIN3 and ORE1 promoted NYE1 and NYC1 transcriptions in an additive manner. These results suggest that ORE1 is also involved in the direct regulation of CCG transcription. Moreover, ORE1 activated the expression of ACS2, a major ethylene biosynthesis gene, and subsequently promoted ethylene production. Collectively, our work reveals that EIN3, ORE1 and CCGs constitute a coherent feed-forward loop involving in the robust regulation of ethylene-mediated chlorophyll degradation during leaf senescence in Arabidopsis.