Department of Genetics, Bio21 Institute, The University of Melbourne, Parkville, Melbourne, Australia.
Mol Biol Evol. 2012 May;29(5):1335-51. doi: 10.1093/molbev/msr294. Epub 2011 Nov 29.
The ability to counter periods of low humidity is an important determinant of distribution range in Drosophila. Climate specialists with low physiological tolerance to desiccation stress are restricted to the tropics and may lack the ability to further increase resistance through evolution. Although the physiological adaptations to desiccation stress are well studied in Drosophila and other ectotherms, factors underlying evolutionary responses remain unknown because of a paucity of genetic data. We address this issue by mapping evolutionary shifts in D. melanogaster under selection for desiccation resistance. Genomic DNA from five independent replicate selected, and control lines were hybridized to high density Affymetrix Drosophila tiling arrays resulting in the detection of 691 single feature polymorphisms (SFPs) differing between the treatments. While randomly distributed throughout the genome, the SFPs formed specific clusters according to gene ontology. These included genes involved in ion transport and respiratory system development that provide candidates for evolutionary changes involving excretory and respiratory water balance. Changes to genes related to neuronal control of cell signaling, development, and gene regulation provide candidates to explore novel biological processes in stress resistance. Sequencing revealed the nucleotide shifts in a subset of the SFPs and highlighted larger regions of genomic diversity surrounding SFPs. The association between natural desiccation resistance and a 463-bp region of the 5' promoter region of the Dys gene undergoing allele frequency changes in response to selection in the experimental evolution lines was tested in an independent population from Coffs Harbour, Australia. The allele frequencies of 23 SNPs common to the two populations were inferred from the parents of the 10% most and 10% least resistant Coffs Harbour flies. The frequencies of the selected alleles were higher at all sites, with three sites significantly associated with the resistant Coffs Harbour flies. This study illustrates how rapid mapping can be used for discovering natural molecular variants associated with survival to low humidity and provides a wealth of candidate alleles to explore the genetic basis of physiological differences among resistant and susceptible Drosophila populations and species.
在果蝇中，抵御低湿度期的能力是决定分布范围的一个重要因素。对干燥胁迫的生理耐受能力较低的气候专家仅限于热带地区，并且可能缺乏通过进化进一步提高抵抗力的能力。尽管在果蝇和其他变温动物中对干燥胁迫的生理适应已有深入研究，但由于遗传数据的缺乏，进化反应的基础因素仍不清楚。我们通过对干燥胁迫选择下的黑腹果蝇进行进化转移的作图来解决这个问题。从五个独立的复制选择和对照系中提取基因组 DNA，然后将其杂交到高密度 Affymetrix 果蝇平铺阵列上，从而检测到处理之间存在 691 个单特征多态性（SFP）。虽然 SFP 随机分布在整个基因组中，但根据基因本体论，它们形成了特定的簇。这些基因包括涉及离子运输和呼吸系统发育的基因，为涉及排泄和呼吸水平衡的进化变化提供了候选基因。与神经元控制细胞信号转导、发育和基因调控相关的基因的变化为探索应激抵抗中的新生物学过程提供了候选基因。测序揭示了 SFP 中的一部分核苷酸变化，并突出了 SFP 周围更大的基因组多样性区域。在澳大利亚科夫斯港的一个独立群体中，测试了自然干燥抵抗与 Dys 基因 5'启动子区域的 463-bp 区域之间的关联，该区域在实验进化系中对选择的反应发生了等位基因频率变化。从对 10%最抗和 10%最不耐受科夫斯港果蝇的父母推断出两个种群中 23 个共同 SNP 的等位基因频率。在所有位点上，选择等位基因的频率都更高，其中三个位点与抗科夫斯港果蝇显著相关。本研究说明了如何快速作图可用于发现与低湿度生存相关的天然分子变体，并提供了丰富的候选等位基因，以探索具有抗性和易感果蝇种群和物种之间生理差异的遗传基础。
