title: The Pseudoautosomal Regions of the U/V Sex Chromosomes of the Brown Alga Ectocarpus Exhibit Unusual Features.
abstract: The recombining regions of sex chromosomes (pseudoautosomal regions, PARs) are predicted to exhibit unusual features due to their being genetically linked to the nonrecombining, sex-determining region. This phenomenon is expected to occur in both diploid (XY, ZW) and haploid (UV) sexual systems, with slightly different consequences for UV sexual systems because of the absence of masking during the haploid phase (when sex is expressed) and because there is no homozygous sex in these systems. Despite a considerable amount of theoretical work on PAR genetics and evolution, these genomic regions have remained poorly characterized empirically. We show here that although the PARs of the U/V sex chromosomes of the brown alga Ectocarpus recombine at a similar rate to autosomal regions of the genome, they exhibit many genomic features typical of nonrecombining regions. The PARs were enriched in clusters of genes that are preferentially, and often exclusively, expressed during the sporophyte generation of the life cycle, and many of these genes appear to have evolved since the Ectocarpales diverged from other brown algal lineages. A modeling-based approach was used to investigate possible evolutionary mechanisms underlying this enrichment in sporophyte-biased genes. Our results are consistent with the evolution of the PAR in haploid systems being influenced by differential selection pressures in males and females acting on alleles that are advantageous during the sporophyte generation of the life cycle.
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, Roscoff, France.
authors.forename: Rémy
authors.initials: R
authors.lastname: Luthringer
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, Roscoff, France.
authors.forename: Agnieszka P
authors.initials: AP
authors.lastname: Lipinska
authors.affiliation: UMI 3614, Evolutionary Biology and Ecology of Algae, CNRS, Sorbonne Universités, UPMC, PUCCh, UACH, Station Biologique de Roscoff, Roscoff, France.
authors.forename: Denis
authors.initials: D
authors.lastname: Roze
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, Roscoff, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Cormier
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, Roscoff, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Macaisne
authors.affiliation: Bezhin Rosko, Santec, France.
authors.forename: Akira F
authors.initials: AF
authors.lastname: Peters
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, Roscoff, France.
authors.forename: J Mark
authors.initials: JM
authors.lastname: Cock
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, Roscoff, France coelho@sb-roscoff.fr.
authors.forename: Susana M
authors.initials: SM
authors.lastname: Coelho
mesh_terms: D000818:Animals; D005075:Biological Evolution; D019143:Evolution, Molecular; D005260:Female; D056426:Genetic Loci; D006238:Haploidy; D008297:Male; D008957:Models, Genetic; D000459:Phaeophyceae / Q000235:genetics*; D011995:Recombination, Genetic; D012730:Sex Chromosomes
keywords: UV sexual system; brown algae; pseudoautosomal region; sex chromosomes