温度选择压力驱动下口虾蛄适应性进化研究

A well-characterized natural environmental gradient in the northwestern Pacific is its steep thermal cline, which largely attributes to the complex current systems with different temperature characteristics. Such obvious temperature heterogeneity can be an important selective force leading to local population adaption of marine organisms. There is no systematic study to evaluate the impact of the temperature heterogeneity on adaptive evolution of marine species in the northwestern Pacific. The Japanese mantis shrimp, Oratosquilla oratoria, can adapt to different thermal environments and exhibits a significant north-south population structure. Thus, it provides an excellent model system for adaptive evolution studies under large scale temperature selective constraint. In this study, we explore the Illumina sequencing technology 1) to examine genetic differentiation pattern and assess the contribution of thermal selection to population differentiation using population genomics approach; 2) to characterize divergence in transcriptome-wide gene expression profiles between north and south populations, and reveal the response relationship between adaptive evolution and temperature pressure; 3) to compare transcriptome differences response to thermal stress between the typical adaptive genotypes grown in high and low temperature habitats, and to find potential genes leading to the adaptive divergence between populations of O. oratoria. This study’s objective is to uncover the genetic basis of adaptive divergence at the genomic level and to understand the genetic mechanisms that underlie population differences in thermal tolerance in O. oratoria by integrating sequence and gene expression information as well as ecological and biological factors. These results would enrich our understanding of molecular mechanism of thermal adaptation in marine ectotherms and the potential impact of global climate change on marine life.

西北太平洋具有复杂多样的洋流系统，使得该海域具有很高的环境温度异质性，这种明显的温度选择压力对海洋生物适应性进化存在如何影响尚无系统研究。口虾蛄能够适应于不同温度的生活环境，且不同种群呈现强烈的遗传分化，是研究宏观海洋温度变化下海洋生物微进化的理想模式物种。本项目在申请人对口虾蛄的研究基础上，采用简化基因组和转录组测序技术，精确解析口虾蛄适应性遗传分化格局，分析温度选择压力对其种群遗传分化的贡献，阐明口虾蛄适应性分化对环境温度压力的响应关系；通过比较两种适温类型响应高温胁迫的转录组差异，筛选可能导致口虾蛄温度适应性分化的关键基因。将口虾蛄不同群体间基因序列变异和表达变异的遗传信息与环境因子、生物学资料整合，揭示口虾蛄适应性分化的遗传基础和南北种群适应不同温度环境的遗传机制。相关研究结果对于阐明海洋生物温度适应性进化的分子机制及全球气候变化对海洋生物的影响具有重要意义。

西北太平洋温度的空间异质性预期会对自然群体造成强烈的选择作用，进而驱动群体的适应性分化。本项目在申请人对口虾蛄的研究基础上，采用种群遗传学研究策略，从遗传变异和表达变异两个层面揭示口虾蛄存在南北差异主导的适应性分化格局，明确空间温度选择压力是重要驱动力，温度选择与种群历史及其他随机因素（洋流、有限基因交流）相互作用共同塑造了口虾蛄当前遗传分化格局。联合同质园实验和转录组分析，发现口虾蛄在高温胁迫下存在组织及时序响应特征。不同纬度分布的地理种群应对热激存在分化的表达可塑性响应模式，生活于高纬度温度高变环境的北方群体，具有更高的转录可塑性，而低纬度南方群体对高温的预适应模式使其具有更高的高温适应能力与热应激转录弹性。口虾蛄可能通过改变能量代谢、细胞凋亡及免疫调节等相关基因的特异性表达产生不同的适应潜力，从而促进其对不同温度生境的适应。本研究作为一个研究范例，揭示了西北太平洋空间温度选择压力驱动下的海洋生物适应性进化及其机制，这为深入探讨海洋生物多样性形成机制以及为预测海洋生物的适应气候变化的潜力提供了重要参考。