Evolution of bric-a-brac regulation in Drosphilinae

描述（由申请人提供）：进化生物学领域长期以来对形态进化的分子基础感兴趣；然而，一个清晰的认识仍然难以捉摸。在果蝇亚群中，腹部色素沉着是一个研究得很好的特征，适合于研究确定遗传变化最终导致相似和不同色素沉着模式的出现。除了不同的色素沉着模式，很明显，基于系统发育，相似的色素沉着模式已经独立出现。在雌雄二态的黑腹蛇种群中，最近进化出了节段特异性色素沉着。雄性的末端腹部节是深色的，而雌性的所有节都是浅色的。密切相关的物种群是单态的，即两性的所有节段都有浅色素。在所有物种中，当色素沉着的抑制因子bric-a-brac （bab）的基因产物表达时，色素沉着就会被阻止。在二态物种中，一种新进化的回路，包括同型异体和性别决定输入，抑制雄性末端段的bab表达，而不是雌性。本研究将分析黑腹果蝇的bab基因调控元件是如何进化以整合对同型异体和性别决定输入的响应性，以及相似和不同的腹部色素模式是如何通过同源bab序列的修饰而进化的。从果蝇中增强子进化和功能的机制中获得的见解很可能适用于理解脊椎动物中的顺式调控元件，因为类似的序列改变在人类中具有重要的医学意义。

DESCRIPTION (provided by applicant): The field of evolutionary biology has long been interested in the molecular basis of morphological evolution; however a clear understanding remains elusive. Abdominal pigmentation in the subgroup Drosophilinae is a well studied trait suitable for studies to identify the genetic changes culminating in the emergence of similar and diverse pigmentation patterns. In addition to diverse pigmentation patterns it is apparent, based on phylogeny, that similar patterns of pigmentation have appeared independently. In the melanogaster species group sexually dimorphic, segment specific pigmentation has recently evolved. The terminal abdominal segments of males are dark, whereas all segments are lightly pigmented in females. Closely related groups of species are monomorphic, i.e. all segments are lightly pigmented in both sexes. In all species, pigmentation is prevented where the gene products of bric-a-brac (bab), a repressor of pigmentation, are expressed. In dimorphic species, a newly evolved circuitry involving homeotic and sex-determination inputs represses bab expression in the terminal segments of the male, but not the female. This proposal will analyze how Drosophila melanogaster bab gene regulatory elements has evolved to integrate responsiveness to homeotic and sex-determination inputs and the extent that both similar and diverse abdominal pigmentation patterns have evolved through the modification of orthologous bab sequences. Insight from the mechanisms of enhancer evolution and function in Drosophilinae will very likely apply to the understanding of cis-regulatory elements in vertebrates as similar sequence alterations have significant medical implications in humans.