果蝇对环境适应的遗传机制与进化模式

生物如何适应复杂多变的环境是进化生物学的核心问题。然而当前对自然群体适应环境的遗传机制的理解仍局限于少数经典案例，对基因型、表型和环境如何相互作用的一般规律尚不明确。果蝇在伴随人类从非洲扩散到世界各地的过程中经历了各种环境压力，是研究自然群体对环境适应的遗传机制和进化模式的绝佳材料。本项目将通过对来自中国不同地区的2000多个黑腹果蝇和拟果蝇品系的 “基因型-表型混合分选测序”(GPPSS)分析，系统鉴定果蝇参与适应寒冷、高温、饥饿和杀虫剂等环境压力的基因位点，并结合CRISPR-Cas9方法进行功能验证。本项目将系统解答下列基本问题：1）生物对环境适应主要依靠新生突变还是既有突变？2）适应是通过改变氨基酸编码还是改变基因表达模式？3）不同群体适应相同环境在遗传机制上是否趋同？研究结果将为物种环境适应机制的研究提供新范式，也将为应对日益严峻的环境变化和杀虫剂抗性等问题提供新的理论参考。

How organisms adapt to complex and changeable environments is a fundamental question in evolutionary biology. Although the genetic mechanisms underlying environmental adaptation have been elegantly dissected for a few cases, the general principle of how genotypes, phenotypes, and environments interact is not yet clear. Drosophila melanogaster and its sibling species Drosophila simulans, which diverged 2-3 million years ago, have experienced various environmental pressures as they spread from Africa to various parts of the world. Thus, natural populations of these two Drosophila species have provided us excellent systems to dissect the genetic mechanisms and evolutionary driving forces underlying environmental adaptation. In this project, we examined 2,000 strains of Drosophila melanogaster and Drosophila simulans that were collected from different locations of China that differ dramatically in environmental factors. We developed a method called GPPSS (genotyping-phenotyping, pooling, sorting, and sequencing) to systematically identify the genetic loci among these strains that are involved in adapting to cold, high temperature, starvation, and insecticides. We will also employ the CRISPR-Cas9 genome-editing technique to validate some candidate loci functionally. We will specifically address the following three fundamental questions in evolutionary biology: 1) Does the organism's adaptation to the environment rely on new mutations or existing mutations? 2) Does organismal adaptation occur by changing the protein sequences or changing the gene expression pattern? 3) Do different species adapt to the same environments through convergent evolution? The study will provide a new paradigm for deciphering the genetic mechanisms and evolutionary forces behind organismal adaptation to environments, and it will also provide novel insights into how to deal with the increasingly deteriorating environmental and pesticide resistance issues.