Jasmonic acid promotes degreening via MYC2/3/4- and ANAC019/055/072-mediated regulation of major chlorophyll catabolic genes.
Jasmonic acid promotes degreening via MYC2/3/4- and ANAC019/055/072-mediated regulation of major chlorophyll catabolic genes.
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DOI：
10.1111/tpj.13030
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发表时间：
2015-11
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影响因子：
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通讯作者：
Xiaoyu Zhu;Junyi Chen;Zuokun Xie;Jiong Gao;Guodong Ren;Shan Gao;Xin Zhou;B. Kuai
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文献类型：
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作者：
Xiaoyu Zhu;Junyi Chen;Zuokun Xie;Jiong Gao;Guodong Ren;Shan Gao;Xin Zhou;B. Kuai
叶绿素 (Chl) 快速降解引起的程度化是绿色器官衰老或成熟过程中的一个特征事件。脱镁叶绿酸加氧酶基因（PAO）编码叶绿素降解的关键酶，但其转录调控仍然很大程度上未知。通过酵母单杂交筛选，结合体外和体内测定，我们发现拟南芥 MYC2/3/4 碱性螺旋-环-螺旋蛋白直接与 PAO 启动子结合。 MYCs的过表达显着增强了拟南芥原生质体中PAO启动子的转录活性，茉莉酸甲酯（MeJA）处理极大地诱导了野生型拟南芥植物中的PAO表达，但在myc2 myc3 myc4中这种诱导作用被消除。此外，MYC2/3/4蛋白可以通过直接结合其启动子来促进另一个叶绿素分解代谢酶基因NYC1以及叶绿素降解的关键调控基因NYE1/SGR1的表达。更重要的是，myc2 myc3 myc4 三重突变体表现出严重的留绿表型，而过表达 MYC 的品系在 MeJA 处理后表现出加速叶片黄化。这些结果表明，MYC2/3/4 蛋白可能通过直接激活这些叶绿素分解代谢基因 (CCG) 来介导茉莉酸 (JA) 诱导的叶绿素降解。 MYC2/3/4 蛋白下游的三个 NAC 家族蛋白 ANAC019/055/072 也可以在叶绿素降解过程中直接促进一组类似的 CCG（NYE1/SGR1、NYE2/SGR2 和 NYC1）的表达。特别是，anac019 anac055 anac072 三重突变体在 MeJA 处理后表现出严重的保持绿色表型。最后，我们发现 MYC2 和 ANAC019 可能相互作用并协同增强 NYE1 的表达。总之，我们的研究揭示了 JA 诱导的叶绿素降解的分层和协调的调控网络。
Degreening caused by rapid chlorophyll (Chl) degradation is a characteristic event during green organ senescence or maturation. Pheophorbide a oxygenase gene (PAO) encodes a key enzyme of Chl degradation, yet its transcriptional regulation remains largely unknown. Using yeast one-hybrid screening, coupled with in vitro and in vivo assays, we revealed that Arabidopsis MYC2/3/4 basic helix-loop-helix proteins directly bind to PAO promoter. Overexpression of the MYCs significantly enhanced the transcriptional activity of PAO promoter in Arabidopsis protoplasts, and methyl jasmonate (MeJA) treatment greatly induced PAO expression in wild-type Arabidopsis plants, but the induction was abolished in myc2 myc3 myc4. In addition, MYC2/3/4 proteins could promote the expression of another Chl catabolic enzyme gene, NYC1, as well as a key regulatory gene of Chl degradation, NYE1/SGR1, by directly binding to their promoters. More importantly, the myc2 myc3 myc4 triple mutant showed a severe stay-green phenotype, whereas the lines overexpressing the MYCs showed accelerated leaf yellowing upon MeJA treatment. These results suggest that MYC2/3/4 proteins may mediate jasmonic acid (JA)-induced Chl degradation by directly activating these Chl catabolic genes (CCGs). Three NAC family proteins, ANAC019/055/072, downstream from MYC2/3/4 proteins, could also directly promote the expression of a similar set of CCGs (NYE1/SGR1, NYE2/SGR2 and NYC1) during Chl degradation. In particular, anac019 anac055 anac072 triple mutant displayed a severe stay-green phenotype after MeJA treatment. Finally, we revealed that MYC2 and ANAC019 may interact with each other and synergistically enhance NYE1 expression. Together, our study reveals a hierarchical and coordinated regulatory network of JA-induced Chl degradation.