ABF2, ABF3, and ABF4 Promote ABA-Mediated Chlorophyll Degradation and Leaf Senescence by Transcriptional Activation of Chlorophyll Catabolic Genes and Senescence-Associated Genes in Arabidopsis
ABF2, ABF3, and ABF4 Promote ABA-Mediated Chlorophyll Degradation and Leaf Senescence by Transcriptional Activation of Chlorophyll Catabolic Genes and Senescence-Associated Genes in Arabidopsis
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DOI：
10.1016/j.molp.2016.06.006
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发表时间：
2016-09-06
期刊：
影响因子：
27.5
通讯作者：
Kuai, Benke
中科院分区：
文献类型：
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作者：
Gao, Shan;Gao, Jiong;Kuai, Benke
叶绿素（Chl）降解是植物叶片衰老的一个重要过程，NYE 1/SGR 1是多种植物Chl降解的关键调节因子。在这项研究中，使用酵母单杂交筛选，我们确定了三个脱落酸（阿坝）响应元件（ABRE）结合转录因子，ABF 2（AREB 1），ABF 3和ABF 4（AREB 2），作为推定的结合蛋白的NYE 1启动子。通过反式激活分析、电泳迁移率变动分析和染色质免疫沉淀，我们证明ABF 2、ABF 3和ABF 4在体外和体内直接结合并激活NYE 1启动子。阿坝是叶片衰老的正调控因子，外源阿坝可加速叶绿素降解。ABF的三突变体abf 2abf 3abf 4以及两个ABA不敏感突变体abi 1 -1和snrk2.2/2.3/2.6在阿坝处理后表现出持绿表型，沿着NYE 1和NYE 2表达的诱导降低。相反，ABF 4的过表达加速了阿坝处理后叶绿素的降解。有趣的是，ABF 2/3/4还可以通过直接结合到两个Chl分解代谢酶基因PAO和NYC 1的启动子来激活它们的表达。此外，abf 2abf 3abf 4表现出功能性的持绿表型，衰老相关基因（SAG），如SAG 29（SWEET 15），可能直接受ABF的调控。综上所述，我们的研究结果表明，ABF 2，ABF 3和ABF 4可能作为介导ABA引发的叶绿素降解和叶片衰老的关键调节因子在拟南芥中。
Chlorophyll (Chl) degradation is an integral process of leaf senescence, and NYE1/SGR1 has been demonstrated as a key regulator of Chl catabolism in diverse plant species. In this study, using yeast one-hybrid screening, we identified three abscisic acid (ABA)-responsive element (ABRE)-binding transcription factors, ABF2 (AREB1), ABF3, and ABF4 (AREB2), as the putative binding proteins of the NYE1 promoter. Through the transactivation analysis, electrophoretic mobility shift assay, and chromatin immunoprecipitation, we demonstrated that ABF2, ABF3, and ABF4 directly bound to and activated the NYE1 promoter in vitro and in vivo. ABA is a positive regulator of leaf senescence, and exogenously applied ABA can accelerate Chl degradation. The triple mutant of the ABFs, abf2abf3abf4, as well as two ABA-insensitive mutants, abi1-1 and snrk2.2/2.3/2.6, exhibited stay-green phenotypes after ABA treatment, along with decreased induction of NYE1 and NYE2 expression. In contrast, overexpression of ABF4 accelerated Chl degradation upon ABA treatment. Interestingly, ABF2/3/4 could also activate the expression of two Chl catabolic enzyme genes, PAO and NYC1, by directly binding to their promoters. In addition, abf2abf3abf4 exhibited a functional stay-green phenotype, and senescence-associated genes (SAGs), such as SAG29 (SWEET15), might be directly regulated by the ABFs. Taken together, our results suggest that ABF2, ABF3, and ABF4 likely act as key regulators in mediating ABA-triggered Chl degradation and leaf senescence in general in Arabidopsis.