Whittle Carrie A, Extavour Cassandra G
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138.
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138
Genetics. 2017 Aug;206(4):2119-2137. doi: 10.1534/genetics.117.201343. Epub 2017 Jun 19.
Males and females exhibit highly dimorphic phenotypes, particularly in their gonads, which is believed to be driven largely by differential gene expression. Typically, the protein sequences of genes upregulated in males, or male-biased genes, evolve rapidly as compared to female-biased and unbiased genes. To date, the specific study of gonad-biased genes remains uncommon in metazoans. Here, we identified and studied a total of 2927, 2013, and 4449 coding sequences (CDS) with ovary-biased, testis-biased, and unbiased expression, respectively, in the yellow fever mosquito The results showed that ovary-biased and unbiased CDS had higher nonsynonymous to synonymous substitution rates (dN/dS) and lower optimal codon usage (those codons that promote efficient translation) than testis-biased genes. Further, we observed higher dN/dS in ovary-biased genes than in testis-biased genes, even for genes coexpressed in nonsexual (embryo) tissues. Ovary-specific genes evolved exceptionally fast, as compared to testis- or embryo-specific genes, and exhibited higher frequency of positive selection. Genes with ovary expression were preferentially involved in olfactory binding and reception. We hypothesize that at least two potential mechanisms could explain rapid evolution of ovary-biased genes in this mosquito: (1) the evolutionary rate of ovary-biased genes may be accelerated by sexual selection (including female-female competition or male-mate choice) affecting olfactory genes during female swarming by males, and/or by adaptive evolution of olfactory signaling within the female reproductive system (, sperm-ovary signaling); and/or (2) testis-biased genes may exhibit decelerated evolutionary rates due to the formation of mating plugs in the female after copulation, which limits male-male sperm competition.
雄性和雌性表现出高度二态性的表型，尤其是在性腺方面，这被认为很大程度上是由基因表达差异驱动的。通常，与雌性偏向和无偏向的基因相比，在雄性中上调的基因（即雄性偏向基因）的蛋白质序列进化得更快。迄今为止，后生动物中对性腺偏向基因的具体研究仍然很少见。在这里，我们分别在黄热病蚊子中鉴定并研究了总共2927个、2013个和4449个具有卵巢偏向、睾丸偏向和无偏向表达的编码序列（CDS）。结果表明，与睾丸偏向基因相比，卵巢偏向和无偏向的CDS具有更高的非同义替换与同义替换率（dN/dS）以及更低的最佳密码子使用频率（即那些促进高效翻译的密码子）。此外，我们观察到，即使对于在非性（胚胎）组织中共表达的基因，卵巢偏向基因中的dN/dS也高于睾丸偏向基因。与睾丸或胚胎特异性基因相比，卵巢特异性基因进化得异常快，并且表现出更高的正选择频率。具有卵巢表达的基因优先参与嗅觉结合和接收。我们假设至少有两种潜在机制可以解释这种蚊子中卵巢偏向基因的快速进化：（1）卵巢偏向基因的进化速率可能通过性选择（包括雌性间竞争或雄性对配偶的选择）而加速，这种性选择在雄性追逐雌性的群体活动中影响嗅觉基因，和/或通过雌性生殖系统内嗅觉信号的适应性进化（即精子 - 卵巢信号传导）；和/或（2）睾丸偏向基因的进化速率可能由于交配后雌性体内形成交配栓而减缓，这限制了雄性间的精子竞争。
