State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangdong Provincial Key Laboratory of Postharvest Science of Fruits and Vegetables, Engineering Research Center of Southern Horticultural Products Preservation, Ministry of Education, College of Horticulture, South China Agricultural University, Guangzhou, China.
Department of Cellular and Structural Biology, UT Health Science Center, San Antonio, Texas.
J Pineal Res. 2019 Aug;67(1):e12570. doi: 10.1111/jpi.12570. Epub 2019 Apr 12.
Melatonin and abscisic acid (ABA) play contrasting roles in regulating leaf senescence in plants. The molecular mechanism underlying the interaction between melatonin and ABA involved in leaf senescence, however, remains poorly defined. Herein, we found that exogenous application of melatonin delayed the senescence of Chinese flowering cabbage, accompanied by reduced expression of chlorophyll catabolic and ABA biosynthetic genes, and a lower endogenous ABA level. Significantly, three nucleus-localized transcriptional activators BrABF1, BrABF4, and BrABI5 were identified, and their expressions were repressed by melatonin. In vitro and in vivo binding experiments revealed that BrABF1, BrABF4, and BrABI5 activated the transcription of a series of ABA biosynthetic and chlorophyll catabolic genes by physically binding to their promoters. Moreover, transient over-expression of BrABF1, BrABF4, and BrABI5 in tobacco leaves induced ABA accumulation and promoted chlorophyll degradation by upregulating tobacco ABA biosynthetic and chlorophyll catabolic genes, resulting in the accelerated leaf senescence. These effects were significantly attenuated by melatonin treatment. Our findings suggest that melatonin-mediated inhibition of leaf senescence involves suppression of ABFs-mediated ABA biosynthesis and chlorophyll degradation. Unraveling of the molecular regulatory mechanism of leaf senescence controlled by ABA and melatonin expands our understanding of the regulation of this phenomenon and offers potentially more effective molecular breeding strategies for extending the shelf-life of Chinese flowering cabbage.
褪黑素和脱落酸（ABA）在植物叶片衰老过程中发挥着相反的作用。然而，褪黑素和 ABA 参与叶片衰老的相互作用的分子机制仍不清楚。在此，我们发现外施褪黑素可延缓白菜花的衰老，同时降低叶绿素降解和 ABA 生物合成基因的表达，ABA 水平也较低。重要的是，鉴定出三个定位于细胞核的转录激活因子 BrABF1、BrABF4 和 BrABI5，它们的表达受褪黑素抑制。体外和体内结合实验表明，BrABF1、BrABF4 和 BrABI5 通过与启动子物理结合，激活一系列 ABA 生物合成和叶绿素降解基因的转录。此外，瞬时过表达烟草叶片中的 BrABF1、BrABF4 和 BrABI5 通过上调烟草 ABA 生物合成和叶绿素降解基因诱导 ABA 积累并促进叶绿素降解，从而加速叶片衰老。褪黑素处理显著减弱了这些效应。我们的研究结果表明，褪黑素介导的抑制叶片衰老涉及抑制 ABFs 介导的 ABA 生物合成和叶绿素降解。阐明 ABA 和褪黑素调控叶片衰老的分子调控机制，扩展了我们对该现象调控的理解，并为延长白菜花货架期提供了潜在更有效的分子育种策略。
