Zareen Shah, Ali Akhtar, Lim Chae Jin, Khan Haris Ali, Park Junghoon, Xu Zheng-Yi, Yun Dae-Jin
Department of Biomedical Science and Engineering, Konkuk University, Seoul, South Korea.
Center of Plant Systems Biology and Biotechnology, Plovdiv, Bulgaria.
Front Plant Sci. 2022 Feb 25;13:828264. doi: 10.3389/fpls.2022.828264. eCollection 2022.
Multiple endogenous and environmental signals regulate the intricate and highly complex processes driving leaf senescence in plants. A number of genes have been identified in a variety of plant species, including Arabidopsis, which influence leaf senescence. Previously, we have shown that HOS15 is a multifunctional protein that regulates several physiological processes, including plant growth and development under adverse environmental conditions. HOS15 has also been reported to form a chromatin remodeling complex with PWR and HDA9 and to regulate the chromatin structure of numerous genes. However, unlike PWR and HDA9, the involvement of HOS15 in leaf senescence is yet to be identified. Here, we report that HOS15, together with PWR and HDA9, promotes leaf senescence transcriptional regulation of senescence marker genes, and photosynthesis-related genes. The expression of , and was downregulated in plants, whereas the expression of photosynthesis-related genes, and , was upregulated. HOS15 also promoted senescence through dark stress, as its mutation led to a much greener phenotype than that of the WT. Phenotypes of double and triple mutants of HOS15 with PWR and HDA9 produced phenotypes similar to those of a single . In line with this observation, the expression levels of , , and were significantly elevated in and mutants compared to those in the WT. Surprisingly, the total H3 acetylation level decreased in age-dependent manner and under dark stress in WT; however, it remained the same in plants regardless of dark stress, suggesting that dark-induced deacetylation requires functional HOS15. More interestingly, the promoters of , , and were hyperacetylated in plants compared to those in WT plants. Our data reveal that HOS15 acts as a positive regulator and works in the same repressor complex with PWR and HDA9 to promote leaf senescence through aging and dark stress by repressing NPX1, APG9, and WRKY57 acetylation.
多种内源性和环境信号调控着驱动植物叶片衰老的复杂且高度 intricate 的过程。在包括拟南芥在内的多种植物物种中已鉴定出许多影响叶片衰老的基因。此前，我们已表明 HOS15 是一种多功能蛋白，可调控多种生理过程，包括在不利环境条件下的植物生长和发育。据报道，HOS15 还与 PWR 和 HDA9 形成染色质重塑复合体，并调控众多基因的染色质结构。然而，与 PWR 和 HDA9 不同，HOS15 在叶片衰老中的作用尚未明确。在此，我们报道 HOS15 与 PWR 和 HDA9 一起，通过对衰老标记基因和光合作用相关基因的转录调控来促进叶片衰老。在 HOS15 缺失的植物中，NPX1、APG9 和 WRKY57 的表达下调，而光合作用相关基因 RbcS 和 Cab 的表达上调。HOS15 还通过黑暗胁迫促进衰老，因为其突变导致比野生型更绿的表型。HOS15 与 PWR 和 HDA9 的双突变体和三突变体产生的表型与单个 HOS15 缺失突变体相似。与此观察结果一致，与野生型相比，在 HOS15 缺失和 HDA9 缺失突变体中，NPX1、APG9 和 WRKY57 的表达水平显著升高。令人惊讶的是，野生型中总 H3 乙酰化水平在衰老依赖的方式下以及在黑暗胁迫下降低；然而，在 HOS15 缺失植物中，无论黑暗胁迫如何，其保持不变，这表明黑暗诱导的去乙酰化需要功能性 HOS15。更有趣的是，与野生型植物相比，在 HOS15 缺失植物中，NPX1、APG9 和 WRKY57 的启动子高度乙酰化。我们的数据表明，HOS15 作为一个正向调节因子，与 PWR 和 HDA9 在同一个阻遏复合体中起作用，通过抑制 NPX1、APG9 和 WRKY57 的乙酰化，在衰老和黑暗胁迫过程中促进叶片衰老。
