褐飞虱致害性变异的遗传分子机理研究

The brown planthopper (BPH, Nilaparvata lugens) is the most destructive rice pest. Resistance breeding is believed to be the most effective method for the control of this pest. However, the fact is that any resistant variaty of rice would lose its resistance soon after its extensively being planted, as the virulence of BPH population will change quickly and develop to a new population (biotype) which adapt to the new rice variaty. Finaly the rice variaty would lose its resistance property completely, some new variety lost its resistance enven shorter than one year. Changeable BPH virulence has been one of the main problems in the resistance breeding and BPH control. Most of the previous studies indicated that the virulence is a hereditary variation, however, its genetic molecular mechanism is unclear. Recently,we completed the sequencing and assembly and annotation of the 3 genomes for BPH, YLS and the main endosymbiont bacterium Arsenophonus, respectively. Based on the sequences of the 3 genomes, this project will mainly study the gene mutation or DNA region variation in the genomes of the BPH populations and their symbionts, of different virulence developed on different rice varieties by individual and population genome re-sequencing method. The selected genes or regions will be further compared using quantitative expression determination, RNAi and bioassay methods. The results will reveal molecular and genetic mechanism of virulence changes of BPH, and provide a basis for the further resistance breeding and developing new stratage for BPH control.

褐飞虱是最主要水稻害虫，抗性育种是最理想的防治措施，然而任1种抗虫水稻品种在大面积推广后，褐飞虱致害性很快就会发生改变，发展为能够适应水稻品种抗性的新种群（生物型），致使抗虫品种丧失其原有的抗性，一些抗虫品种的使用寿命甚至不超过一年，成为褐飞虱防治及抗虫育种工作中面临的主要难题。此前种种研究迹象表明，褐飞虱致害性变异是可遗传的，但其遗传变异的分子基础并不清楚，严重制约了抗虫育种和品种利用管理。最近我们分别完成了褐飞虱、内共生真菌和内共生细菌全基因组序列测定和组装注释分析，取得了重要进展。本项目拟在此基础上，用平行基因组重测序方法研究褐飞虱在不同抗性水稻品种上发生致害性变异与褐飞虱种群和其胞内共生真菌和共生细菌的基因组遗传结构变化，结合分析相关基因表达变化、RNAi和生物学测定，阐明褐飞虱致害性变化的遗传分子机制，为水稻抗性育种和褐飞虱防治提供重要依据

褐飞虱是水稻最主要害虫，抗性育种是最经济的防治措施，然而每种抗虫水稻品种在大面积田间推广后，褐飞虱致害性很快就会发生改变，发展为能够适应水稻品种抗性的新种群（生物型），致使抗虫品种丧失其原有的抗性，有的抗虫品种的使用寿命甚至不超过一年，成为褐飞虱防治及抗虫育种工作中面临的主要难题。然而致害性变异的分子基础并不很清楚。本项目在褐飞虱基因组完成基础上进行深入研究，取得如下结果：①对不同致害性褐飞虱种群个体基因组重测序揭示了褐飞虱致害性不同在基因组遗传变异上的分化,并筛选出了在水稻抗性品种的选择压力下出现明显变化的42个候选基因；②通过质谱分析、基因表达变化、RNAi和生物学测定揭示了褐飞虱的唾液蛋白组成和相关编码基因功能，发现了NlMul等唾液蛋白基因及其表达水平在褐飞虱克服水稻抗性方面发挥重要功能。③进一步深入分析了共生真菌YLS的基因组，明确了其与昆虫病原性的真菌冬虫夏草菌近缘，并命名为 “Entomomyces delphacidicola str. NLU”；代谢通路分析 揭示了“稻飞虱-共生真菌”在必需氨基酸合成、氮循环、甾类和维生素合成等代谢通路存在基因互补关系，这使得专一性取食营养不均匀水稻汁液的稻飞虱能够猖獗地为害水稻。④发现不同地理种群的致害性存在差异，较为纯合的褐飞虱种群在不同抗性水稻上长期饲养也会出现遗传分化。⑤褐飞虱致害性种群扩散与褐飞虱迁飞能力密切相关，稻飞虱若虫会根据环境发育为能迁飞的长翅型成虫和不能迁飞但繁殖能力很强的短翅型成虫,我们揭示了翅芽中2个胰岛素受体是这种可塑性发育的分子开关。以上结果初步阐明褐飞虱致害性变化的遗传分子机制，为水稻抗性育种和褐飞虱防治提供重要依据。 部分结果已经发表在Nature, PNAS、Genome Biology and Evolution、Molecular Ecology、Genetics 和各种昆虫学TOP杂志上。翅型可塑性发育的分子开关成果入选“2015中国生命科学领域十大进展”。