Transcriptomics of Intralocus Sexual Conflict: Gene Expression Patterns in Females Change in Response to Selection on a Male Secondary Sexual Trait in the Bulb Mite

Abstract

Intralocus sexual conflict (IASC) prevents males and females from reaching their disparate phenotypic optima and is widespread, but little is known about its genetic underpinnings. In Rhizoglyphus robini, a mite species with alternative male morphs, elevated sexual dimorphism of the armored fighter males (compared to more feminized scramblers males) was previously reported to be associated with increased IASC. Because IASC persists if gene expression patterns are correlated between sexes, we compared gene expression patterns of males and females from the replicate lines selected for increased proportion of fighter or scrambler males (F- and S-lines, respectively). Specifically, we tested the prediction that selection for fighter morph caused correlated changes in gene expression patterns in females. We identified 532 differentially expressed genes (FDR < 0.05) between the F-line and S-line males. Consistent with the prediction, expression levels of these genes also differed between females from respective lines. Thus, significant proportion of genes differentially expressed between sexually selected male phenotypes showed correlated expression levels in females, likely contributing to elevated IASC in F-lines reported in a previous study.

Male-limited secondary sexual trait interacts with environment in determining female fitness

“…Our results could suggest that the negative pleiotropic effects of the male SST on female fitness were exacerbated in highly stressful environments such as 28°C, but not in environments in which the stress was milder. This could be explained by the higher sensitivity of sexually selected phenotypes to stress (Berger et al 2014b), coupled with the pleiotropic effect of SSTs on female fitness (Plesnar-Bielak et al 2014;Joag et al 2016). Another interpretation of our results is that whether gender load is increased or decreased in a novel environment depends on the precise properties of a given environment rather than on the magnitude of stress it imposes on a population (see also Delcourt et al 2009;Punzalan et al 2014).…”

“…; Joag et al. ). Another interpretation of our results is that whether gender load is increased or decreased in a novel environment depends on the precise properties of a given environment rather than on the magnitude of stress it imposes on a population (see also Delcourt et al.…”

“…One prediction would be that the previously reported correlation in gene expression patterns between fighter males and females (Joag et al. ), which was thought to underlie the increase in IASC, has weakened.…”

“…Furthermore, Joag et al. () found that selection for male morphs influenced the expression of over 500 genes (associated with a variety of organismal processes), and the expression profiles of these genes also significantly changed in females, indicating that widespread pleiotropic effects were associated with the male SST. If sexually selected phenotypes are more sensitive to the stress associated with a novel environment (Sheldon et al.…”

“…Temperature is a key factor affecting ectotherm metabolism (Angilletta 2009), and morph-specific and sex-specific gene expression analyses have indicated that genes involved in metabolic processes are indeed associated with sexually antagonistic selection in fighters (Stuglik et al 2014). Furthermore, Joag et al (2016) found that selection for male morphs influenced the expression of over 500 genes (associated with a variety of organismal processes), and the expression profiles of these genes also significantly changed in females, indicating that widespread pleiotropic effects were associated with the male SST. If sexually selected phenotypes are more sensitive to the stress associated with a novel environment (Sheldon et al 1998;Bussière et al 2008;Berger et al 2014a), then, owing to intersexual genetic correlations, female fitness should be more affected by the novel thermal environment in the F-lines.…”