Data from: Two genomic regions together cause dark abdominal pigmentation in Drosophila tenebrosa

Pigmentation is a rapidly evolving trait that is under both natural and sexual selection in many organisms. In the quinaria group of Drosophila, nearly all of the 30 species have an abdomen that is light in color with distinct markings; D. tenebrosa is the exception in that it has a completely melanic abdomen with no visible markings. In this study, we use a combination of quantitative genetic and candidate gene approaches to investigate the genetic basis of abdominal pigmentation in D. tenebrosa. We find that abdominal pigmentation is invariant across wild- caught lines of D. tenebrosa and is not sexually dimorphic. Quantitative genetic mapping utilizing crosses between D. tenebrosa and the light-colored D. suboccidentalis indicates that two genomic regions together underlie abdominal pigmentation, including the X-chromosome and an autosome (Muller Element C/E). Further support for their central importance in pigmentation is that experimental introgression of one phenotype into the other species, in either direction, results in introgression of these two genomic regions. Finally, the expression of the X- linked gene yellow in the pupae exactly foreshadows the adult melanization pattern in the abdomen of both species, suggesting that changes in the regulation of yellow are important for the phenotypic divergence of D. tenebrosa from the rest of the quinaria group. These results contribute to a body of work that demonstrates how changes in expression of highly conserved genes can cause substantial phenotypic differences even between closely related species.

色素沉着是一类快速演化的性状，在多数生物中同时受到自然选择与性选择的双重作用。在果蝇属（Drosophila）的quinaria类群（quinaria group）中，已记录的30余个物种几乎均拥有色泽浅淡且带有清晰斑纹的腹部；暗黑果蝇（D. tenebrosa）是唯一例外，其腹部完全呈黑化状态，无任何可见斑纹。本研究结合定量遗传学与候选基因策略，探究暗黑果蝇腹部色素沉着的遗传基础。研究发现，暗黑果蝇野生捕获品系的腹部色素沉着性状均一稳定，且不存在性二态性。利用暗黑果蝇与浅色物种近西果蝇（D. suboccidentalis）进行杂交的定量遗传定位结果表明，两个基因组区域共同调控腹部色素沉着，分别位于X染色体与一条常染色体（穆勒元件C/E（Muller Element C/E））。进一步验证这两个区域在色素沉着中核心重要性的实验证据为：将任一物种的腹部色素沉着表型双向导入另一物种时，均会伴随这两个基因组区域的渐渗事件。最后，X连锁基因黄色基因（yellow）在蛹期的表达模式恰好预示了两个物种成虫腹部的黑化模式，这提示黄色基因的调控变化是驱动暗黑果蝇与quinaria类群其余物种表型分化的关键因素。本研究结果补充了现有研究体系，证明即便是亲缘关系极近的物种之间，高度保守基因的表达调控变化也可引发显著的表型差异。