通过比较转录组学和适应性进化分析探索对虾的盐度适应性机制

As an important environment factor, salinity plays an important role in affecting shrimps growth, survival, respiratory metabolism and immune defense. Shrimps living in seawater or freshwater must have different salinity adaption mechanisms, and also generate a cluster of genes with adaptive features. Most penaeid shrimps are euryhaline species, which is superior than freshwater shrimps in adaption to the salinity variations. However, present researches on shrimps salinity adaptation mechanisms are limited in differential expression analysis on the genes of single species, but rarely on the differential expression pattern and adaptive evolution analyses between freshwater and seawater shrimps. In this project, we decide to perform transcritpome sequencing on freshwater and seawater shrimps with different salinity stress, and find the differences of expression patterns between them. Besides, adaptive evolution analysis will also perform on all the orthologous unigenes of shrimps with transcriptome data. Then, several important osmoregulation related genes with the characters of positive selected and differential expressed will be collected. Finally, real-time quantitative PCR and gene silencing experiments can be implemented to prove the crucial function of these genes in shrimps salinity adaptation. This study will contribute to the eclucidation of salinity adaptation mechanisms in penaeid shrimps, and provide a theoretical basis for resistant breeding and hypohaline culture of shrimps.

盐度是对虾养殖过程中影响其生长、存活、呼吸代谢和免疫防御的一个非常重要的环境因子。对虾普遍属于广盐性物种，相比淡水虾具有更强的盐度适应能力。为了适应各自的水环境，海水虾和淡水虾都会诞生出各自的盐度适应性机制，也会产生一批适应性进化的基因。然而目前对于对虾盐度适应性机制的研究仅限于单一物种盐度胁迫前后的差异表达分析，对于海水虾和淡水虾基因表达模式的差异以及基因的适应性进化却鲜有报导。本项目将对海水虾和淡水虾进行盐度胁迫转录组测序，通过比较转录组学手段，探索两类虾表达模式的差异；然后结合已公布虾类转录组数据进行全基因组范围基因的适应性进化分析，挑选其中受正选择作用且盐度胁迫差异表达的渗透调控相关基因，通过定量PCR和RNA干扰实验，验证其在对虾不同盐度环境适应中的关键作用，为揭示对虾盐度适应机制奠定基础，进而为对虾的抗逆选育及淡化养殖提供理论依据。

为了适应各自的水环境，海水虾和淡水虾都会诞生出各自的盐度适应性机制，但是其各自的渗透调控机制还不是很清楚。本课题对凡纳滨对虾、中国明对虾、脊尾白虾三种虾类进行了盐度耐受实验和转录组测序，发现了三种虾类盐度耐受的差异，通过对差异基因表达模式的分析，发现了三种虾类各自独特的渗透调控机制。对虾主要通过自由氨基酸来调节渗透平衡，而脊尾白虾则通过热激蛋白（HSP70）的应激响应来进行渗透调控。基于已有转录组数据，我们进行了海水虾和淡水虾适应性进化分析，找到了各自渗透调控相关的正选择基因，揭示了海水虾渗透调控系统趋同进化的特征。最后，通过实验对部分关键渗透调控基因在不同组织应对急性和适应盐度胁迫过程中的作用进行了验证，揭示了这些基因在鳃和触角腺的渗透调控过程中的重要作用。本研究通过比较转录组学和适应性进化分析手段，鉴定了部分关键渗透调控基因，为虾类渗透调控机制的解析提供了宝贵的数据基础，初步探索了不同虾类独特的渗透调控机制，为经济虾类水产养殖和遗传育种的研究提供了基础。