Gamete differentiation : a genetic, biochemical and evolutionary study using Ectocarpus siliculosus

Despite its prevalence among eukaryotes, there are still many questions awaiting answers and plenty of discoveries to be made with regard to the mechanisms and maintenance of sexual reproduction. Brown algae (Phaeophyceae) represent a very interesting group to study the evolution of sexual reproduction, owing to the rich variation of life cycles, fertilization modes and sex determination systems displayed by this lineage. Particularly unique are various degrees of sexual dimorphism between gametes of closely related species, ranging from isogamy through anisogamy to oogamy. Therefore, the opportunity to compare these systems on the molecular level in Phaeophyceae promises advancement in our understanding of the evolution of sexual reproduction not only in algae, but in all living organisms. In this thesis we investigated the molecular basis of sexual reproduction and its link to reproductive isolation using a brown algal model organism Ectocarpus siliculosus. We constructed whole transcriptome libraries of male and female gametes to explore their functional differentiation at the gene expression level. We sequenced sex biased genes in a representative number of strains from distant geographical locations and varying stages of reproductive isolation, to search for signatures of positive selection. This thesis has offered the first insight into protist gametes transcriptomes, revealing complex, functional organization and differentiation according to the adopted sexual roles, as well as evolutionary variation of sex biased genes. Our study supports the relevance of algal systems in the research of sexual reproduction and provides a starting point for more exciting discoveries in that field.

Jaar van publicatie:2013

Toegankelijkheid:Open