Evolution of bric-a-brac regulation in Drosphilinae

描述(申请人提供)：进化生物学领域长期以来一直对形态进化的分子基础感兴趣；然而，一个清晰的理解仍然难以捉摸。果蝇亚群的腹部色素沉着是一个经过充分研究的特征，适合于研究最终导致相似和不同的色素模式出现的遗传变化。除了不同的色素沉着模式外，根据系统发育，很明显，相似的色素沉着模式已经独立出现。在黑腹蛇种群中，性二型、节段性色素沉着最近已经进化。雄性的腹部末端是深色的，而雌性的所有腹部都是浅色的。密切相关的物种群是单形性的，即所有节段在两性中都有轻微的色素。在所有物种中，在表达色素沉着抑制因子brc-a-brac(Bab)的基因产物的地方，色素沉着是被阻止的。在二态物种中，一种涉及同源异型和性别决定输入的新进化回路抑制了Bab在雄性末端节段的表达，但不抑制雌性的表达。这项提案将分析果蝇BAB基因调控元件如何进化，以整合对同源和性别决定输入的反应，以及通过修改同源BAB序列，进化出相似和不同的腹部色素模式的程度。对果蝇亚科增强子进化和功能机制的深入了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.