脱落酸和茉莉酸调控转录因子OsMYC2介导的水稻抗褐飞虱机制

Myelocytomatosis proteins (MYC2) transcription factor is the activation transcription factor of plant jasmonic acid (JA), which is activated by mechanical injury and insect feeding. The studies showed that the expression of MYC2 in Arabidopsis thaliana increased after exogenous abscisic acid (ABA), which increased resistance to chewing pest. The brown planthopper (BPH), Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) sucks the phloem juice and causes destruction of rice crops, our previous studies had shown that rice resistance to BPH increased after exogenous ABA treatments, and ABA contents increased and JA contents decreased in rice after exogenous ABA treatments and BPH feeding, and the expression of OsMYC2 gene decreased, so OsMYC2 transcription factor may negatively mediate the phytohormone signaling pathway to respond to BPH. In this project, we use rice treated by exogenous ABA and JA, and ABA, JA and OsMYC2 overexpression and knockdown plants to explore ABA- and JA-regulated resistance mechanism to BPH mediated by OsMYC2. The studies include the interaction between ABA and JA, and the resistance to pest in rice after ABA and JA treatments, and the effects of OsMYC2 on transcriptome, defense genes and rice resistance to pest. The interaction between ABA and JA makes a new exploration on the mechanism of inducing rice resistance to BPH, and it will offer the theory support for developing micromolecule alternative pesticides to replace ABA in agriculture and also provide a scientific basis for the new practice of controlling other sucking pest.

髓细胞组织增生蛋白MYC2是植物茉莉酸（JA）的激活转录因子，由机械伤害及昆虫取食后被激活。在对咀嚼式口器昆虫的研究中发现外源脱落酸（ABA）增强了拟南芥MYC2的表达，提高了抗虫性。褐飞虱刺吸韧皮部汁液危害水稻，我们前期研究发现外源ABA处理增强了水稻的抗虫性；外源ABA处理、褐飞虱侵害后，水稻ABA含量显著上升，JA含量显著下降，OsMYC2表达显著下降，表明该转录因子在防御褐飞虱侵害中可能起到负调控作用。本项目在此基础上拟利用外施ABA、JA，构建ABA、JA、OsMYC2转基因突变体，研究ABA和JA调控OsMYC2介导的水稻抗虫性，包括ABA与JA互作及对抗虫性的影响；OsMYC2对水稻转录组、防御基因及抗虫性的影响。本研究将从ABA与JA的互作上为诱导水稻抗褐飞虱机理做出新的探索，并为研制ABA小分子替代物的研发提供了理论支持，还为其它刺吸式口器害虫防治的新实践提供科学依据。

MYC2是植物茉莉酸（JA）的激活转录因子，由机械损伤及害虫取食后被激活。在对咀嚼式口器昆虫的研究中发现外源脱落酸（ABA）增强了拟南芥转录因子MYC2的表达，提高了抗虫性。褐飞虱是一种刺吸式口器害虫，在水稻叶鞘韧皮部吸取汁液威胁水稻。ABA作为一种胁迫型激素，在生物侵害早期诱导植物体产生防御反应，抵御生物的侵害。MYC2可以诱导水稻提高对褐飞虱的抗性，喷施ABA可诱导JA通路OsMYC2水平的提高，OsMYC2在植株不同时期、部位的表达量不同，在苗期叶鞘中表达量最高，说明OsMYC2在水稻幼苗期有重要调控作用。通过CRISPR-Cas9技术以及将OsMYC2连接过表达载体，构建了osmyc2过表达植株及敲除突变体植株，突变体不论在苗期或分蘖期都比WT长势更好，平均受害级别、植株功能损失指数比WT高，易受褐飞虱侵害；EPG分析表明褐飞虱在osmyc2敲除突变体植株上停留及取食时间均更长。由此说明，OsMYC2在水稻抗褐飞虱过程中起到重要性的作用。为了探究OsMYC2与下游哪些因素有关导致水稻对褐飞虱产生抗性，通过转录组分析表明，在osmyc2敲除突变体中共有上千个基因产生了变化，基因富集分析确定了在ABA通路的PYLs有显著性变化，通过酵母双杂交手段验证了OsMYC2与PYLs共12个基因互作验证，确定了PYL3、PYL4、PYL5、PYL10、PYL12与OsMYC2存在互作作用。由此表明，OsMYC2通过与PYLs互作，诱导了水稻ABA含量提高，从而达到抗褐飞虱的效果。本研究从ABA和JA调控转录因子OsMYC2介导水稻抗褐飞虱机制研究,为水稻抗虫性机理作出新的探索，并为未来品种的选育作出新的探索，还为其它刺吸式口器害虫防治的新实践提供科学依据。