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Zusammenfassung:
Red algae belong to the oldest evolutionary lineages of photosynthetic eukaryotes and comprise one of the largest phyla of algae on the planet. Most of the red algal species are multicellular and macroscopic, live in marine environment and have a complex life history with alternation of three, rather than two, generations. Particularly interesting are the aspects of the evolution of sex determination during the haploid life stage (UV sex chromosomes). However, the sex chromosomes in red algae have never been described to date. Here, we use high-quality genomic and transcriptomic datasets and comparative genomics from three species of red algae to provide the first analysis of the red algal UV sex chromosomes. We characterized the genomic architecture and gene content of both the female (U) and the male (V) sex chromosomes and their nonrecombining regions, and we investigated sex biased gene expression in order to understand sexual differentiation in this group of organisms. The UV system in these red algae shows distinct evolutionary history not only from the well-studied XY and ZW systems but also from the other algal UV systems described so far. Nevertheless, some striking similarities exist, indicating the universality of the underlying processes shaping sex chromosome evolution across major eukaryotic supergroups.
