稻纵卷叶螟幼虫热适应的调控机理

Based on the situation that population outbreaks of the rice leaf folders become more and more frequent and the results found in previous studies of the applicant that the larvae of rice leaf folder have strong behavioral and physiological strategies to adapt to high temperature, the heat tolerance, heritability of heat adaptation, variations of transcriptome, and functions of differentially expressed genes of these larvae exposed to high temperature for different generations will be studied in this project. The results will highlight the genetic characteristics of phenotype on heat adaptation. Integrating the biological traits and gene expression during the three stages of heat acclimation: heat reception, heat response and heat adaptation, the formation of heat adaptation and related physiological pathways and genes will be illustrated. In previous studies, the applicant found that the enriched GO terms were sensory organ development, structural constituent of eye lens, structural constituent of cuticle and oxidoreductase activity. Consequently, in this project, the functions of genes related to heat shock proteins, cuticle proteins, glucose dehydrogenase and ecdysone oxidase will be studied, and the molecular mechanism of heat adaptation of larvae will be known. The results of this project not only can enrich the theory of insect adaptation and evolution, but also can unfold the reasons of frequent outbreaks of the rice leaf folder populations under global warming. The study has great values in theory and practice.

基于稻纵卷叶螟种群在全球变暖大形势下暴发成灾更为频繁的现状，结合申请者前期发现稻纵卷叶螟幼虫具有行为和生理上的高温适应策略的结果，本项目通过测定高温锻炼不同代次后稻纵卷叶螟幼虫的耐热能力、热适应力的遗传、转录组变异和热适应相关基因的功能等，明确稻纵卷叶螟幼虫高温适应性的表型遗传特征；整合幼虫在热感受、热应激和热适应三环节中的生物学特性和基因表达水平，阐明昆虫适应高温过程中激发的主要代谢通路与基因。利用前期工作中已发现高温锻炼与热击导致幼虫感受器发育、表皮结构组成、眼晶体结构组成以及氧化还原酶活性等相关基因的差异表达结果，本项目采用基因克隆、表达和干扰等技术测定热激蛋白、表皮蛋白、葡糖脱氢酶和蜕皮激素氧化酶基因在幼虫热适应中的功能作用，阐明昆虫热适应的分子机理。研究结果既可丰富昆虫的适应与进化理论，又可明确全球变暖形势下稻纵卷叶螟种群暴发成灾频繁的原由，研究具有较高的理论和实际应用价值。

稻纵卷叶螟是水稻上的重要害虫，以前的研究表明该虫不耐高温，但是在全球变暖背景下，该虫暴发成灾频率呈上升趋势，因此本项目推测该虫对高温存在适应对策，并开展了其幼虫热适应调控机理研究。研究表明，稻纵卷叶螟幼虫经39℃热锻炼4-5代后即可适应该高温，并且经锻炼驯化获得的耐热能力具有一定的传代效应，并能杂交遗传。热锻炼品系和不锻炼品系经41℃高温处理1h后的转录组分析发现了2675个差异表达基因，并且热锻炼品系比不锻炼品系引起了更多基因的差异表达。两品系差异表达基因主要富集于氧化还原酶活性相关的GO分类中。高温锻炼提高了幼虫表皮蛋白和脂质的含量，干扰表皮蛋白基因CmTweedle1和CmCPG1显著降低了表皮蛋白含量并提高了幼虫在高温下的存活率，这两个表皮蛋白基因与幼虫的热适应性相关，表皮中高含量的表皮蛋白是幼虫应对高温的物理屏障。热锻炼提高了幼虫受热击后热激蛋白基因的表达，干扰HSP70或HSP90后，显著降低了热锻炼品系幼虫在高温下的存活率，但对不锻炼品系的影响较小。热锻炼也影响了幼虫氧化还原酶基因的表达水平，幼虫受41℃高温热击后，氧化还原酶基因CmGMC10在热锻炼品系中的表达水平显著高于不锻炼品系，但CmGMC38则相反，并且这两基因主要在幼虫体壁和头部高表达。干扰CmGMC10基因引起了热锻炼品系幼虫在高温下存活率的显著下降及幼虫体内ROS水平的显著上升，但对不锻炼品系的影响小；而干扰CmGMC38后对不锻炼品系幼虫影响大，而对热锻炼品系影响小。CmGMC10基因与幼虫的热适应相关联。研究结果阐明了稻纵卷叶螟幼虫具有热适应性，并且表皮蛋白CmTweedle1和CmCPG1、热激蛋白HSP70和HSP90、氧化还原酶基因CmGMC10联合参与了幼虫热适应过程，形成了以高表皮蛋含量的物理热屏障和以高热激蛋白和低ROS水平的生理屏障双重保护的热适应机制。研究结果不仅丰富了昆虫热适应理论，而且阐明了全球变暖下稻纵卷叶螟因产生热适应而频繁暴发的原因。