Academic journal article Genetics

Rapid Evolution of Ovarian-Biased Genes in the Yellow Fever Mosquito (Aedes Aegypti)

Academic journal article Genetics

Rapid Evolution of Ovarian-Biased Genes in the Yellow Fever Mosquito (Aedes Aegypti)

Article excerpt

SEX-BIASED genes, that is, genes whose expression is upregulated in one sex relative to the other, are believed to underlie sexual dimorphism and have been extensively reported in anisogamous eukaryotes including mammals, birds, fish, insects, worms, fungi, higher plants, and algae (Meiklejohn et al. 2003; Ranz et al. 2003; Zhang et al. 2004; Cutter and Ward 2005; Yang et al. 2006; Ellegren and Parsch 2007; Haerty et al. 2007; Whittle et al. 2007; Small et al. 2009; Assis et al. 2012; Parsch and Ellegren 2013; Whittle and Johannesson 2013; Lipinska et al. 2015; Wang et al. 2015). The number of genes exhibiting sex bias can represent a majority of the genome, with estimates from 50 to >75% of the genome being sex-biased in insect genera such as Drosophila and Nasonia (Ranz et al. 2003; Ellegren and Parsch 2007; Assis et al. 2012; Wang et al. 2015). The sex biases in expression appear to have molecular evolutionary consequences. For example, in animals studied to date, malebiased genes typically evolve more rapidly at the protein sequence level, exhibiting elevated ratios of nonsynonymous to synonymous substitutions (dN/dS), than female-biased or unbiased genes [reviewed by Ellegren and Parsch (2007); see also Mank et al. (2007) and Parsch and Ellegren (2013)]. Evidence suggests that sex biases in expression between whole individuals might largely result from the sex-limited organs, namely gonads and their contained sex cells (Arbeitman et al. 2002, 2004; Parisi et al. 2004; Ellegren and Parsch 2007; Small et al. 2009; VanKuren and Vibranovski 2014). This is consistent with the fact that the gonads comprise highly differentiated organs, with extremely divergent transcriptomes, between males and females (Parisi et al 2004; Harrison et al. 2015). In this regard, gonadal gene expression may largely shape the evolution of many proteincoding genes.

Genes expressed in the gonads are believed to play a central role in evolution, contributing toward reproductive success and fitness, reproductive isolation, and speciation. These genes are also most apt to be influenced by major evolutionary processes such as sexual conflict, mate-choice, and intrasexual competition (Civetta and Singh 1998; Swanson and Vacquier 2002; Jagadeeshan and Singh 2005; Ellegren and Parsch 2007; Turner and Hoekstra 2008). With respect to molecular evolution of reproductive and gonad genes, studies in animals including mammals and insects have shown that certain seminal protein genes (Swanson et al. 2001), testis (Good and Nachman 2005; Khaitovich et al. 2005; Ellegren and Parsch 2007; Haerty et al. 2007), and sperm genes (Torgerson et al. 2002; Good and Nachman 2005; Ellegren and Parsch 2007; Haerty et al. 2007) typically evolve rapidly as compared to the rest of the genome, and thus agree with the global pattern of rapid sequence evolution of male-biased genes. Specific testis and ovary genes directly involved in fertilization have also been demonstrated to evolve rapidly in various animal systems (Civetta and Singh 1998; Swanson and Vacquier 2002). Nonetheless, observed effects of expression within sex and reproductive genes varies among studies and with the type of tissue examined. For example, seminal fluid protein sequences evolve fast in numerous models including Drosophila species (Haerty et al. 2007), but not in others such as A. albopictus (Boes et al. 2014), and while spermatogenesis genes typically evolve rapidly (including in Drosophila) (Ellegren and Parsch 2007; Haerty et al. 2007), some fly research suggests that sperm genes may be more conservative in their rates of evolution (Dorus et al. 2006). In this regard, while male reproductive genes typically evolve rapidly, this may not be universal to all male sexual tissues, and the signal varies to some extent among organisms and studies.

At present, studies in animals that specifically compare whole testis- vs. ovary-biased expression and its effect on the evolution of protein-coding DNA remain few, with the exception of some examples from organisms such as guppies (Poecilia: Sharma et al. …

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.