%0 Journal Article %J Genome Biology and Evolution %D 2021 %T Evolutionary Genomics of Sex-Related Chromosomes at the Base of the Green Lineage %A Benites, Luis Felipe %A Bucchini, François %A Sanchez-Brosseau, Sophie %A Grimsley, Nigel %A Vandepoele, Klaas %A Piganeau, Gwenael %E Wolfe, Kenneth %K RCC1105 %K RCC1115 %K RCC2590 %K RCC299 %K rcc3401 %K RCC4221 %K RCC809 %K RCC834 %X Although sex is now accepted as a ubiquitous and ancestral feature of eukaryotes, direct observation of sex is still lacking in most unicellular eukaryotic lineages. Evidence of sex is frequently indirect and inferred from the identification of genes involved in meiosis from whole genome data and/or the detection of recombination signatures from genetic diversity in natural populations. In haploid unicellular eukaryotes, sex-related chromosomes are named mating-type (MTs) chromosomes and generally carry large genomic regions where recombination is suppressed. These regions have been characterized in Fungi and Chlorophyta and determine gamete compatibility and fusion. Two candidate MTþ and MTÀ alleles, spanning 450–650 kb, have recently been described in Ostreococcus tauri, a marine phytoplanktonic alga from the Mamiellophyceae class, an early diverging branch in the green lineage. Here, we investigate the architecture and evolution of these candidate MTþ and MTÀ alleles. We analyzed the phylogenetic profile and GC content of MT gene families in eight different genomes whose divergence has been previously estimated at up to 640 Myr, and found evidence that the divergence of the two MT alleles predates speciation in the Ostreococcus genus. Phylogenetic profiles of MT transspecific polymorphisms in gametologs disclosed candidate MTs in two additional species, and possibly a third. These Mamiellales MT candidates are likely to be the oldest mating-type loci described to date, which makes them fascinating models to investigate the evolutionary mechanisms of haploid sex determination in eukaryotes. %B Genome Biology and Evolution %V 13 %P evab216 %G eng %U https://academic.oup.com/gbe/article/doi/10.1093/gbe/evab216/6380139 %R 10.1093/gbe/evab216 %0 Journal Article %J Science Advances %D 2020 %T Virus-host coexistence in phytoplankton through the genomic lens %A Yau, Sheree %A Krasovec, Marc %A Benites, L. Felipe %A Rombauts, Stephane %A Groussin, Mathieu %A Vancaester, Emmelien %A Aury, Jean-Marc %A Derelle, Evelyne %A Desdevises, Yves %A Escande, Marie-Line %A Grimsley, Nigel %A Guy, Julie %A Moreau, Hervé %A Sanchez-Brosseau, Sophie %A Van de Peer, Yves %A Vandepoele, Klaas %A Gourbière, Sébastien %A Piganeau, Gwenael %K RCC2590 %K RCC2596 %X Virus-microbe interactions in the ocean are commonly described by “boom and bust” dynamics, whereby a numerically dominant microorganism is lysed and replaced by a virus-resistant one. Here, we isolated a microalga strain and its infective dsDNA virus whose dynamics are characterized instead by parallel growth of both the microalga and the virus. Experimental evolution of clonal lines revealed that this viral production originates from the lysis of a minority of virus-susceptible cells, which are regenerated from resistant cells. Whole-genome sequencing demonstrated that this resistant-susceptible switch involved a large deletion on one chromosome. Mathematical modeling explained how the switch maintains stable microalga-virus population dynamics consistent with their observed growth pattern. Comparative genomics confirmed an ancient origin of this “accordion” chromosome despite a lack of sequence conservation. Together, our results show how dynamic genomic rearrangements may account for a previously overlooked coexistence mechanism in microalgae-virus interactions. %B Science Advances %V 6 %P eaay2587 %8 apr %G eng %U https://advances.sciencemag.org/lookup/doi/10.1126/sciadv.aay2587 %R 10.1126/sciadv.aay2587 %0 Journal Article %J Genome Biology and Evolution %D 2019 %T First estimation of the spontaneous mutation rate in Diatoms %A Krasovec, Marc %A Sanchez-Brosseau, Sophie %A Piganeau, Gwenael %E Baer, Charles %K diatoms %K Mutation accumulation %K mutation rate in phaeodactylum %K mutation spectrum %K phaeodactylum %K RCC2967 %K running title %K spontaneous mutation rate %K tricornutum %B Genome Biology and Evolution %V 1 %P 1–23 %G eng %U https://academic.oup.com/gbe/advance-article/doi/10.1093/gbe/evz130/5520952 %R 10.1093/gbe/evz130