Evolutionary Genetics: Contribution of Tan to Drosophila Pigmentation Divergence

描述（由申请人提供）：该项目的长期目标是了解表型进化的遗传和分子机制。这包括发现负责表型差异的基因，确定这些基因中哪些变化会影响表型，并确定这些变化如何改变分子，细胞和发育过程。利用遗传作图和转基因分析相结合的初步研究表明，两个密切相关的果蝇物种，D。americana和D. novamexicana，（部分）是由tan基因内的分歧引起的。tan编码催化N-β-丙氨酰-多巴胺转化为多巴胺的酶，这是产生多巴胺黑色素的必要步骤。精细遗传作图确定了一个仅包含非编码差异的tan区域，这表明物种之间不同的tan表达有助于色素分化，并且在D. americana比D. novamexicana。拟议项目的目标是定位棕褐色内影响色素沉着的所有不同位点，并确定它们如何改变色素沉着的发展。具体而言，本提案的目的是：（1）确定影响色素沉着的种特异性tan等位基因之间的核苷酸差异，（2）确定这些变化在D. novamexicana和D. americana，以及（3）确定这些位点如何影响tan mRNA和蛋白质表达。本项目中使用的转基因方法允许直接比较基因型之间的差异少至一个核苷酸，并在多个物种中的转基因分析允许顺式和反式调节变化负责tan分歧得到解决。完成后，该项目将提高我们对复杂性状表型差异的遗传变化和分子机制的总体理解。

DESCRIPTION (provided by applicant): The long-term goal of this project is to understand the genetic and molecular mechanisms underlying phenotypic evolution. This includes discovering the genes responsible for phenotypic divergence, identifying which changes within these genes affect the phenotype, and determining how these changes alter molecular, cellular, and developmental processes. Preliminary studies using a combination of genetic mapping and transgenic analysis show that pigmentation differences between two closely related Drosophila species, D. americana and D. novamexicana, are caused (in part) by divergence within the tan gene. tan encodes an enzyme that catalyzes the conversion of N-beta-alanyl-dopamine into dopamine, which is a necessary step for the production of dopamine melanin. Fine-scale genetic mapping identified a region of tan containing only non-coding differences, which suggests that divergent tan expression between species contributes to pigmentation divergence, and greater abundance of tan mRNA was observed in D. americana than D. novamexicana. The goal of the proposed project is to locate all divergent sites within tan that affect pigmentation and to determine how they alter pigmentation development. Specifically, the aims of this proposal are to: (1) identify nucleotide differences between species-specific tan alleles that affect pigmentation, (2) determine the phenotypic consequences of these changes in D. novamexicana and D. americana, and (3) determine how these sites affect tan mRNA and protein expression. Transgenic approaches used in this project allow direct comparisons between genotypes that differ for as little as one nucleotide, and the analysis of transgenes in multiple species allows cis- and trans-regulatory changes responsible for tan divergence to be resolved. When completed, this project will improve our general understanding of the genetic changes and molecular mechanisms underlying phenotypic differences in complex traits.