Biology subjects

Mossion, V.

Publications and source records attributed to Mossion, V..

3 recordsLinked to original sources

bioRxiv2023

The Silene latifolia genome and its giant Y chromosome

In some species, the Y is a tiny chromosome but the dioecious plant Silene latifolia has a giant [~]550 Mb Y chromosome, which has remained unsequenced so far. Here we used a hybrid approach to obtain a high-quality male S. latifolia genome. Using mutants for sexual phenotype, we identified candidate sex-determining genes on the Y. Comparative analysis of the sex chromosomes with outgroups showed the Y is surprisingly rearranged and degenerated for a [~]11 MY-old system. Recombination suppression between X and Y extended in a stepwise process, and triggered a massive accumulation of repeats on the Y, as well as in the non-recombining pericentromeric region of the X, leading to giant sex chromosomes. One-Sentence SummaryThis work uncovers the structure, function, and evolution of one of the largest giant Y chromosomes, that of the model plant Silene latifolia, which is almost 10 times larger than the human Y, despite similar genome sizes.

genomics↗

bioRxiv2022

Global diversification of the common moonwort ferns (Botrychium lunaria group, Ophioglossaceae) was mainly driven by Pleistocene climatic shifts

The cosmopolitan Botrychium lunaria group belong to the most species rich genus of the family Ophioglossaceae and was considered to consist of two species until molecular studies in North America and northern Europe led to the recognition of multiple new taxa. Recently, additional genetic lineages were found scattered in Europe, emphasizing our poor understanding of the global diversity of the B. lunaria group, while the processes involved in the diversification of the group remain unexplored. We conducted the first global phylogenetic study of the group including 513 ingroup accessions sequenced for four non-coding plastid loci. We recovered ten well-supported clades, although relationships between clades were inconsistent between Bayesian and Maximum Likelihood analyses. We treated each clade at the species level, except for one clade including two ploidy levels, resulting in the recognition of 11 species, 5 of which are unnamed. In contrast to previous studies, we found species diversity to be equally distributed across the northern hemisphere, with 7-8 species per continent. We estimated the stem age of the B. lunaria group at 2.4-5.1 million years, with most species 1.8-2.6 million years old, and subspecies 0.5-1.0 million years old. Diversification thus coincided with Pleistocene climatic fluctuations that strongly affected the areas inhabited by the group, suggesting that diversification was driven by climatically induced cycles of extinction, dispersal, and migration. Furthermore, ecological differentiation between species suggests these complex population dynamics were associated with adaptations to specific environmental conditions. We found limited evidence that speciation is driven by polyploidization and hybridization. We show that the B. lunaria group has greater species level diversity than previously assumed and suspect that further cryptic species may await discovery, especially in the B. neolunaria clade.

evolutionary biology↗

bioRxiv2020

A reference transcriptome for the early-branching fern Botrychium lunaria enables fine-grained resolution of population structure

Ferns are the second most dominant group of land plants after angiosperms. Extant species occupy an extensive range of habitats and contribute significantly to ecosystem functioning. Despite the importance of ferns, most taxa are poorly covered by genomic resources. The genus Botrychium belongs to the family Ophioglossaceae, one of the earliest divergent lineages of vascular plants, and has a cosmopolitan distribution with 35 species, half of which are polyploids. Here, we establish a transcriptome for Botrychium lunaria, a diploid species with an extremely large genome with a 1C value of 12.10 pg. We assembled 25,701 high-quality transcripts with an average length of 1,332 bp based on deep RNA-sequencing of a single individual. We sequenced an additional 11 transcriptomes of individuals from two populations in Switzerland, including the population of the reference individual. Based on read mapping to reference transcript sequences, we identified 374,510 single nucleotide polymorphisms (SNPs) segregating among individuals for an average density of 14 SNPs per kb. The transcriptome-wide markers provided unprecedented resolution of the population genetic structure revealing substantial variation in heterozygosity among individuals. We also constructed a phylogenomic tree of 90 taxa representing all fern orders to ascertain the placement of the genus Botrychium. The high-quality transcriptomic resources enable powerful population and phylogenomic studies in an important group of ferns. Significance statementFerns pose substantial puzzles in terms of lifestyles, genome organization and population structure. Progress has been significantly hampered by the lack of genomic resources. Here, we present a transcriptome for Botrychium lunaria, a phylogenetically early-branching fern with an extremely large genome. We show that the new transcriptome improves phylogenetic resolution among early-branching ferns. Based on an additional 11 transcriptomes of the same species, we identify unexpected variation in population-level heterozygosity.

genomics↗