Gubala Anna M, Schmitz Jonathan F, Kearns Michael J, Vinh Tery T, Bornberg-Bauer Erich, Wolfner Mariana F, Findlay Geoffrey D
Department of Biology, College of the Holy Cross, Worcester, MA.
Evolutionary Bioinformatics Group, Institute for Evolution and Biodiversity, University of Münster, Münster, Germany.
Mol Biol Evol. 2017 May 1;34(5):1066-1082. doi: 10.1093/molbev/msx057.
New genes arise through a variety of mechanisms, including the duplication of existing genes and the de novo birth of genes from noncoding DNA sequences. While there are numerous examples of duplicated genes with important functional roles, the functions of de novo genes remain largely unexplored. Many newly evolved genes are expressed in the male reproductive tract, suggesting that these evolutionary innovations may provide advantages to males experiencing sexual selection. Using testis-specific RNA interference, we screened 11 putative de novo genes in Drosophila melanogaster for effects on male fertility and identified two, goddard and saturn, that are essential for spermatogenesis and sperm function. Goddard knockdown (KD) males fail to produce mature sperm, while saturn KD males produce few sperm, and these function inefficiently once transferred to females. Consistent with a de novo origin, both genes are identifiable only in Drosophila and are predicted to encode proteins with no sequence similarity to any annotated protein. However, since high levels of divergence prevented the unambiguous identification of the noncoding sequences from which each gene arose, we consider goddard and saturn to be putative de novo genes. Within Drosophila, both genes have been lost in certain lineages, but show conserved, male-specific patterns of expression in the species in which they are found. Goddard is consistently found in single-copy and evolves under purifying selection. In contrast, saturn has diversified through gene duplication and positive selection. These data suggest that de novo genes can acquire essential roles in male reproduction.
新基因通过多种机制产生，包括现有基因的复制以及从非编码DNA序列中从头诞生基因。虽然有许多具有重要功能作用的复制基因的例子，但从头基因的功能在很大程度上仍未被探索。许多新进化的基因在雄性生殖道中表达，这表明这些进化创新可能为经历性选择的雄性提供优势。利用睾丸特异性RNA干扰技术，我们在黑腹果蝇中筛选了11个假定的从头基因对雄性生育力的影响，并鉴定出两个基因，即戈达德（goddard）和土星（saturn），它们对精子发生和精子功能至关重要。敲低戈达德基因（KD）的雄性无法产生成熟精子，而敲低土星基因的雄性产生的精子很少，并且这些精子转移到雌性体内后功能效率低下。与从头起源一致，这两个基因仅在果蝇中可识别，预计编码的蛋白质与任何注释蛋白质没有序列相似性。然而，由于高度的差异阻止了明确鉴定每个基因起源的非编码序列，我们认为戈达德和土星是假定的从头基因。在果蝇中，这两个基因在某些谱系中已经丢失，但在发现它们的物种中显示出保守的、雄性特异性的表达模式。戈达德基因始终以单拷贝形式存在，并在纯化选择下进化。相比之下，土星基因通过基因复制和正选择而多样化。这些数据表明，从头基因可以在雄性生殖中获得重要作用。
