Department of Entomology, Rutgers University , New Brunswick, NJ , USA.
PeerJ. 2015 Feb 26;3:e807. doi: 10.7717/peerj.807. eCollection 2015.
Culex pipiens, an invasive mosquito and vector of West Nile virus in the US, has two morphologically indistinguishable forms that differ dramatically in behavior and physiology. Cx. pipiens form pipiens is primarily a bird-feeding temperate mosquito, while the sub-tropical Cx. pipiens form molestus thrives in sewers and feeds on mammals. Because the feral form can diapause during the cold winters but the domestic form cannot, the two Cx. pipiens forms are allopatric in northern Europe and, although viable, hybrids are rare. Cx. pipiens form molestus has spread across all inhabited continents and hybrids of the two forms are common in the US. Here we elucidate the genes and gene families with the greatest divergence rates between these phenotypically diverged mosquito populations, and discuss them in light of their potential biological and ecological effects. After generating and assembling novel transcriptome data for each population, we performed pairwise tests for nonsynonymous divergence (Ka) of homologous coding sequences and examined gene ontology terms that were statistically over-represented in those sequences with the greatest divergence rates. We identified genes involved in digestion (serine endopeptidases), innate immunity (fibrinogens and α-macroglobulins), hemostasis (D7 salivary proteins), olfaction (odorant binding proteins) and chitin binding (peritrophic matrix proteins). By examining molecular divergence between closely related yet phenotypically divergent forms of the same species, our results provide insights into the identity of rapidly-evolving genes between incipient species. Additionally, we found that families of signal transducers, ATP synthases and transcription regulators remained identical at the amino acid level, thus constituting conserved components of the Cx. pipiens proteome. We provide a reference with which to gauge the divergence reported in this analysis by performing a comparison of transcriptome sequences from conspecific (yet allopatric) populations of another member of the Cx. pipiens complex, Cx. quinquefasciatus.
库蚊是一种侵袭性蚊子，也是美国西尼罗河病毒的传播媒介，它有两种形态上无法区分的形式，在行为和生理上有很大的差异。Cx. pipiens form pipiens 主要是一种以鸟类为食的温带蚊子，而亚热带的 Cx. pipiens form molestus 则在污水中茁壮成长，并以哺乳动物为食。由于野生型在寒冷的冬季可以休眠，但家栖型不能，因此这两种 Cx. pipiens 形式在北欧是异地的，尽管可行，但杂种很少见。Cx. pipiens form molestus 已经传播到所有有人居住的大陆，这两种形式的杂种在美国很常见。在这里，我们阐明了这些表型分化的蚊子种群之间具有最大分歧率的基因和基因家族，并根据它们的潜在生物学和生态学影响对它们进行了讨论。在为每个种群生成和组装新的转录组数据后，我们对同源编码序列的非同义分歧率 (Ka) 进行了成对测试，并检查了在具有最大分歧率的序列中统计上过度代表的基因本体术语。我们鉴定了参与消化（丝氨酸内肽酶）、先天免疫（纤维蛋白原和α-巨球蛋白）、止血（D7 唾液蛋白）、嗅觉（气味结合蛋白）和几丁质结合（围食膜蛋白）的基因。通过检查同一物种的密切相关但表型分化形式之间的分子分歧，我们的结果为快速进化基因在初生种间的身份提供了线索。此外，我们发现信号转导、ATP 合酶和转录调节因子家族在氨基酸水平上保持相同，因此构成了 Cx. pipiens 蛋白质组的保守成分。我们通过比较 Cx. pipiens 复合体的另一个成员 Cx. quinquefasciatus 的同种（但异地）种群的转录组序列，提供了一个参考，以衡量本分析中报告的分歧。
