Astrid Groot de l'Institut pour la biodiversité et la dynamique des écosystèmes (IBED) de l’Université d’Amsterdam, invitée par Foteini Koutroumpa, nous présentera ses travaux de recherche.
Abstract:
Our overall research revolves around the question of the evolution of sexual attraction contributes to speciation. Moths are ideal animals to study how sex pheromones evolve, because females of every species produce their own species-specific pheromone blend in a specified gland that can be chemically analysed relatively easily. Also, there are ~130.000 moth species (compare that to ~5500 mamal species), females can lay 500 - 1000 eggs enabling inheritance analyses, and moths can be reared in the lab so that the effects of say infections, different food sources and stress on sex pheromones can be investigated.
Given the limited availability of resources in nature, the development and maintenance elaborate sexually selected traits or signals are often costly. The immunocompetence handicap hypothesis (ICHH) posits that sexual attractiveness trades off with immunocompetence. In vertebrates, testosterone appears to be involved in both immunosuppression and in the brightness of sexual signals. However, such a direct link has not been found yet in invertebrates. We assessed how parasitic infection (of the neogregarine parasite Ophryocystis elektroscirrha) affect the sexual signals in the noctuid moth Chloridea virescens (Lepidoptera, Noctuidae), where we found variation in attraction. After selecting on their differences in sex pheromone composition and generating an attractive and an unattractive line, we found that the unattractive line was significantly less susceptible to parasite infection than the attractive line. Since the sexual attractiveness between these two lines is determined by a delta-11-desturase, we hypothesized that this desaturase plays a dual role in immune function and in the quality of the sexual signal. However, when we knocked out this gene in the High line, using CRISPR/cas9, we found that the pheromonal phenotype did change to that of the unattractive line, but the infection susceptibility did not. Interestingly, in the C. virescens genome, mucin is adjacent to delta-11-desaturase, and we found structural differences in this gene between the two selection lines. These differences suggest that genetic hitchhiking could be a potential mechanism underlying the variation in susceptibility to parasitic infection.
