Causes and Consequences of Size Evolution in Drosophila melanogaster

描述（由申请人提供）：本研究调查了新发现的高海拔种群黑腹果蝇（Drosophila melanogaster）的遗传基础、细胞机制和身体和翅膀大小进化的发育后果，黑腹果蝇是该物种中已知最大的果蝇。这一特性提供了独特的机会，将生物学上重要的表型差异与其潜在的细胞机制以及导致这种变化的特定基因和突变联系起来。从种群基因组数据到转基因工具，果蝇系统为在遗传水平上研究适应性进化提供了一系列优势。结果将增加我们对适应的多基因性和致病变异特性的认识（例如编码与调节；新突变与原有遗传变异）。该研究整合了生物学分支学科，揭示了细胞水平的机制（如细胞增殖和体细胞倍性），负责表型进化。它还罕见地探讨了适应性进化对发育稳定性的潜在影响。这项工作将揭示进化如何改变参与胰岛素信号和细胞周期的基因功能，而不会对生物体造成有害后果——这些发现可能最终被证明与癌症、糖尿病和其他医学疾病的研究相关。1. 进行全基因组搜索，寻找在体型进化中起作用的基因。使用转基因技术确认其效果并测试致病突变。一种新的QTL定位方法将致病基因定位到~100kb的尺度。一项新的群体遗传统计数据将揭示QTL区间内的基因，这些基因显示了高地样本中群体特异性选择的证据（初始异常值包括胰岛素信号基因）。鉴定出的基因将使用一种新开发的转基因方法对身体和翅膀大小的影响进行功能测试；特定的突变将以同样的方式进行测试。2. 揭示体型进化背后的细胞机制。研究人员将测试细胞大小和数量的变化是否会导致埃塞俄比亚D. melanogaster惊人的大翅膀。研究还将证实观察到的幼虫肌肉（多核细胞，强烈影响成年体的大小）的扩大是由于细胞核数量的增加还是其倍性的增加。转基因结构将允许细胞的影响

DESCRIPTION (provided by applicant): This research investigates the genetic basis, cellular mechanisms, and developmental consequences of body and wing size evolution in a newly discovered high altitude population of Drosophila melanogaster which represents the largest known flies of this species. This trait offers the unique opportunity to relate a biologically important phenotypic difference to its underlying cellular mechanisms and to specific genes and mutations responsible for this change. The Drosophila system offers a range of advantages to study adaptive evolution at the genetic level, from population genomic data to transgenic tools. Results will increase our knowledge of the polygenicity of adaptation and the properties of causative variants (e.g. coding vs. regulatory; new mutations vs. standing genetic variation). This research integrates biological subdisciplines to reveal cell-level mechanisms (e.g. cell proliferation and somatic ploidy) responsible for phenotypic evolution. It also takes a rare look a the potential influence of adaptive evolution on developmental stability. This work will reveal how evolution has altered the function of genes involved in insulin signaling and the cell cycle without harmful consequences to the organism - findings that may ultimately prove relevant for research on cancer, diabetes, and other medical conditions. 1. Conduct a genome-wide search for genes that play a role in body size evolution. Confirm their effects and test causative mutations using transgenesis. A novel QTL mapping method will localize causative genes to the ~100kb scale. A new population genetic statistic will reveal genes within QTL intervals that show evidence of population-specific selection in the highland sample (initial outliers include insulin signaling genes). Genes identified will be functionally tested for influence on body and wing size using a newly developed transgenic approach; specific mutations will be tested in the same way. 2. Reveal cellular mechanisms underlying body size evolution. Research will test whether changes in both cell size and number may give rise to the strikingly large wings of Ethiopian D. melanogaster. Research will also confirm whether the observed enlargement of larval muscles (polynucleate cells which strongly influence adult body size) is due to increases in the number of nuclei or their ploidy. Transgenic constructs will allow the cellular influence of specific adaptive mutations to be assessed. 3. Test whether wing size evolution disrupted developmental canalization. Ethiopian inbred lines show large wings but also very high frequencies of wing vein abnormalities. The hypothesis that phenotypic evolution has destabilized a more developmentally buffered ancestral wing state will be directly tested using a mutagenesis test of genetic perturbility. Artificial selection to recapitulate wing size evolution n the lab will further probe the generality of a link between adaptation and decanalization.