南京农大万建民团队鉴定水稻小褐飞虱易感基因

灰飞虱(SBPH)不仅直接危害作物，而且还是水稻条纹病毒(RSV)和水稻黑条矮缩病毒(RBSDV)等毁灭性病害的载体，严重影响水稻产量。植物具有复杂的抗虫响应调控网络，已知的飞虱抗性基因多为富含亮氨酸重复序列(LRR)家族成员或表面定位模式识别受体。组蛋白的翻译后修饰(PTMs)参与调节多种生物过程，已有研究证明植物组蛋白H3甲基化参与病原体防御反应，而PTMs与抗虫的关联尚不清楚。

南京农业大学万建民、刘裕强团队通过筛选水稻T-DNA插入突变体，发现了飞虱易感突变体phs1。该突变体中含SET(Su (var)3-9、Enhancer-of-zeste和Trithorax)保守结构域的SDG703蛋白表达量提高，可见编码该蛋白的基因能够增强水稻对灰飞虱的易感性。SDG703在多种组织中组成性表达，并在灰飞虱摄食下表现出显著上调。Western Blot实验与烟草瞬时表达结果证明SDG703具有组蛋白H3K9甲基化转移酶活性。转录组学分析显示，在过表达SDG703的植物中，参与效应触发免疫(ETI)和模式触发免疫(PTI)的相关基因下调。Chip-Seq qPCR结果证实，SDG703过表达水稻植株中这些下调表达基因的H3K9甲基化水平显著高于野生型。

这项研究证实SDG703通过促进组蛋白甲基化抑制防御相关基因的表达，从而导致水稻对灰飞虱的抗性降低。该研究为植物抗虫性的表观遗传调控提供了新的见解。

Int J Mol Sci, August 21 2023

SET Domain Group 703 Regulates Planthopper Resistance by Suppressing the Expression of Defense-Related Genes

Author

Wen P, He J, Zhang Q……Wang Y, Liu Y*, Wan J*.

*: State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, Jiangsu Nanjing Rice Germplasm Resources National Field Observation and Research Station, Jiangsu Provincial Research Center of Plant Gene Editing Engineering, Nanjing Agricultural University, China

Abstract

Plant defense responses against insect pests are intricately regulated by highly complex regulatory networks. Post-translational modifications (PTMs) of histones modulate the expression of genes involved in various biological processes. However, the role of PTMs in conferring insect resistance remains unclear. Through the screening of a T-DNA insertion activation-tagged mutant collection in rice, we identified the mutant planthopper susceptible 1 (phs1), which exhibits heightened expression of SET domain group 703 (SDG703). This overexpression is associated with increased susceptibility to the small brown planthopper (SBPH), an economically significant insect pest affecting rice crops. SDG703 is constitutively expressed in multiple tissues and shows substantial upregulation in response to SBPH feeding. SDG703 demonstrates the activity of histone H3K9 methyltransferase. Transcriptomic analysis revealed the downregulation of genes involved in effector-triggered immunity (ETI) and pattern-triggered immunity (PTI) in plants overexpressing SDG703. Among the downregulated genes, the overexpression of SDG703 in plants resulted in a higher level of histone H3K9 methylation compared to control plants. Collectively, these findings indicate that SDG703 suppresses the expression of defense-related genes through the promotion of histone methylation, consequently leading to reduced resistance against SBPH. The defense-related genes regulated by histone methylation present valuable targets for developing effective pest management strategies in future studies. Furthermore, our study provides novel insight into the epigenetic regulation involved in plant-insect resistance.