Abstract
Sexual reproduction is a pervasive phenomenon in nearly all eukaryotic lineages. In genetically controlled sexual systems, sex is determined by sex chromosomes, which have emerged independently and repeatedly during evolution. We are exploiting the exceptional richness of sexual features of the brown algae to gain novel insights into the evolution of sex determination in this group of organisms. The sex-chromosomes of several brown algal species that have diverged over a 160-MY time frame were compared, and this analysis has revealed the unique evolutionary, structural and gene expression patterns of these genomic regions compared with autosomes. Finally, using the brown alga model Ectocarpus sp., we have revealed how the sex chromosomes, together with autosomal loci, play a critical role not only on sex determination and differentiation but also on the regulation of other key reproductive process such as asexual reproduction via gamete parthenogenesis.
