小RNA介导的飞蝗表型可塑性的母性效应

Maternal effect refers that the phenotype of an organism is influenced by the genotype and environment of its mother. The maternal effect is significant to the offspring to adaptive to environment and to the evolution of the population. The mechanisms of maternal effect include hormone, epigenetic modification of the genome, noncoding RNA regulation. The migratory locust is an important agricultural pest, which can transit between gregarious and solitarious phases. And the characteristics of the two phases of locusts could be passed from the parents to the offsprings. Therefore, the locust is an ideal model to study the maternal effect. Previous studies have demonstrated that the egg size and synchronized hatching of the progeny are regulated by the genes or small RNAs of the mother locusts. However, the pathway of the small RNAs transmission from the mothers to the offsprings is unclear. In addition, the functions of the maternally transmitted small RNAs need further studies. This study will identify the maternally transmitted small RNAs by high-throughput sequencing of the small RNA (20 -100 nt) in the oocytes, follicle cells and early eggs. The aim of the study is to investigate the transmission of the small RNAs from mothers to the offsprings, and the function of small RNAs in the progeny development. Meanwhile, the study will explore the mechanisms of the germline small RNAs response to the population density changes. The study will not only explore the important mechanisms of transgenerational plasticity meditated by small RNAs, but provide important theory basis for new methods of pest control.

母性效应是指生物体后代表型受到母亲基因型和母亲所经历环境的共同影响，对生物体后代适应环境、种群进化意义重大。母性效应可由激素、基因组表观修饰以及非编码RNA等因素的调控。飞蝗是重要农业害虫，它们在种群密度变化的条件下能够在群居型和散居型之间相互转变并且飞蝗两型相关的表型特征能够通过母代传递给后代，因此飞蝗是研究母性效应的理想模型。前期研究已证明卵粒大小及孵化一致性等都可由母代基因或非编码RNA调控。但是，小RNA从母代传递到后代具体机制还不清楚，其功能也需要更深入的研究。本研究将从飞蝗卵母细胞、膜泡细胞和早期卵内长度为20-100 nt的小RNA大规模测序、鉴定入手，探究小RNA从飞蝗母代向后代的传递路径以及对后代发育的调控功能，同时探索生殖系统小RNA响应外界种群密度变化的机制。本研究不仅揭示由小RNA介导的跨代传递调控的重要机制，而且为开发害虫控制新方法提供重要理论依据。

由环境导致的母性效应在自然界普遍存在并且对生物体后代适应环境、种群进化意义重大。飞蝗在种群密度变化下形成的群居散居两种截然不同的种群形式具有明显跨代效应，是研究母性效应的良好模型。我们前期研究结果证明，小RNA在飞蝗两型转变和母本对后代孵化一致性调控具有重要功能。本项目立足已有研究基础，利用高通测序，探究参与调控群散飞蝗母性效应的小RNA及这些生殖系统小RNA响应种群密度变化的机制。我们将飞蝗母本来源、父本来源及后代受精卵的非编码小RNA表达谱进行大规模分析比较，得知飞蝗各类小RNA在群散飞蝗中不存在明显父性传递效应而只存在母性效应。其中，piRNA具有明显的母性效应表达模式，它们在群居母本和后代卵中均发生表达上调。进一步，我们通过对群散飞蝗受精卵和未受精卵进行转录组测序，力图找到差异表达piRNA的靶标基因，从而探索它们的功能。经过互补配对将群散差异表达基因与piRNA进行靶标预测得到，群居上调的基因中，piRNA靶向代谢相关基因，而散居上调基因中，piRNA靶向转座子基因。下一步将对这些上调表达的小RNA在群居和散居雌虫体内分别进行过抑制和过表达，检测它们对于后代卵发育的调控功能。同时我们还将在体内外进行实验验证这些piRNA的靶标基因。另外，我们还以已经发现的控制群散飞蝗卵孵化一致性的microRNA miR-276为例，对飞蝗卵巢响应种群密度变化的机制进行深入研究。经过对前前体pri-miR-276、前体pre-miR-276及成熟体miR-276的定量检测，我们得知飞蝗群居卵巢miR-276的高表达主要是由末端卵母细胞pre-miR-276较高出核效率导致。这种出核效率由一个群居飞蝗末端卵母细胞高表达的HEPH蛋白特异性介导。由此我们得到群居高表达的HEPH介导的pre-miR-276高效出核效率，从而导致的miR-276在群居卵巢的高表达。