The Chromatin Remodeler SPLAYED Regulates Specific Stress Signaling Pathways

Organisms are continuously exposed to a myriad of environmental stresses. Central to an organism's survival is the ability to mount a robust transcriptional response to the imposed stress. An emerging mechanism of transcriptional control involves dynamic changes in chromatin structure. Alterations in chromatin structure are brought about by a number of different mechanisms, including chromatin modifications, which covalently modify histone proteins; incorporation of histone variants; and chromatin remodeling, which utilizes ATP hydrolysis to alter histone-DNA contacts. While considerable insight into the mechanisms of chromatin remodeling has been gained, the biological role of chromatin remodeling complexes beyond their function as regulators of cellular differentiation and development has remained poorly understood. Here, we provide genetic, biochemical, and biological evidence for the critical role of chromatin remodeling in mediating plant defense against specific biotic stresses. We found that the Arabidopsis SWI/SNF class chromatin remodeling ATPase SPLAYED (SYD) is required for the expression of selected genes downstream of the jasmonate (JA) and ethylene (ET) signaling pathways. SYD is also directly recruited to the promoters of several of these genes. Furthermore, we show that SYD is required for resistance against the necrotrophic pathogen Botrytis cinerea but not the biotrophic pathogen Pseudomonas syringae. These findings demonstrate not only that chromatin remodeling is required for selective pathogen resistance, but also that chromatin remodelers such as SYD can regulate specific pathways within biotic stress signaling networks.

生物体始终暴露于海量的环境胁迫之中。生物体存活的核心要素，便是能够对施加的胁迫启动强劲的转录应答反应。当前日渐受到关注的一类转录调控机制，涉及染色质结构的动态变化。染色质结构的改变由多种不同机制介导，包括对组蛋白进行共价修饰的染色质修饰、组蛋白变体的掺入，以及利用ATP水解释能以改变组蛋白-DNA相互作用的染色质重塑。尽管学界已对染色质重塑的机制积累了相当多的认知，但染色质重塑复合物除作为细胞分化与发育的调控因子之外的其他生物学功能，至今仍未得到充分阐明。本研究通过遗传学、生物化学与生物学实验证据，证实了染色质重塑在介导植物对抗特定生物胁迫的过程中发挥关键作用。我们发现，拟南芥SWI/SNF家族染色质重塑ATP酶SPLAYED (SYD)是茉莉酸 (JA)与乙烯 (ET)信号通路下游部分靶基因表达所必需的。SYD还可被直接招募至上述部分基因的启动子区域。此外，实验证实SYD对于植物对抗死体营养型病原体灰葡萄孢菌 (Botrytis cinerea)的抗性不可或缺，但对活体营养型病原体丁香假单胞菌 (Pseudomonas syringae)的抗性则无此要求。本研究结果不仅证明了染色质重塑是植物获得选择性病原抗性的必要条件，同时也揭示了诸如SYD这类染色质重塑因子，能够调控生物胁迫信号网络中的特定通路。