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。这包括发现导致表型差异的基因，确定这些基因中的哪些变化影响表型，以及确定这些变化如何改变分子、细胞和发育过程。采用遗传作图和转基因分析相结合的初步研究表明，两个近缘关系密切的果蝇物种--美洲果蝇和新果蝇之间的色素差异(部分)是由tan基因的差异造成的。Tan编码一种酶，催化N-β-丙氨酰多巴胺转化为多巴胺，这是产生多巴胺黑色素的必要步骤。精细的遗传作图发现了一个仅包含非编码差异的tan区域，这表明物种之间tan表达的差异是导致色素差异的原因之一，并且在美洲盾叶蝉中观察到的tan mRNA的丰度高于D.novamiciana。这项拟议项目的目标是定位TAM内所有影响色素沉着的不同部位，并确定它们如何改变色素沉着的发展。具体地说，这项建议的目的是：(1)确定影响色素沉着的物种特异性tan等位基因之间的核苷酸差异，(2)确定这些变化在D.novamiciana和D.americana中的表型后果，以及(3)确定这些位置如何影响tan mRNA和蛋白的表达。该项目中使用的转基因方法允许在差异小至一个核苷酸的基因类型之间进行直接比较，并且对多个物种中的转基因进行分析可以解决导致tan差异的顺式和反式调节变化。这个项目完成后，将提高我们对复杂性状表型差异背后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.