Biology subjects

Coriton, O.

Publications and source records attributed to Coriton, O..

5 recordsLinked to original sources

bioRxiv2025

Nissolia brasiliensis as a non-nodulating model legume

The nitrogen-fixing root nodule symbiosis (RNS) is specifically formed by four orders of angiosperms. The largest of these four orders include the legume family, the Fabaceae. Among legumes, historical model species have emerged, such as the RNS-forming Medicago truncatula and Lotus japonicus, or, more recently, Aeschynomene aevenia. By contrast, legume species that have lost RNS have been largely ignored. Here, we describe the first chromosome-level assembly for a non-RNS-forming legume, the tropical papilionoid Nissolia brasiliensis. We compared its genome to closely related legumes and identified genes associated with RNS. Finally, we developed a stable transformation protocol that can be deployed in the future to re-evolve RNS in legumes, a first step toward the goal of engineering RNS in non-legume crops.

plant biology↗

bioRxiv2024

Playing with the ploidy level enables to switch on and off the strict recombination control even in the vicinity of Brassica centromeres

Meiotic recombination is a key biological process in plant evolution and breeding, as it generates novel genetic diversity at each generation. However, due to its importance in chromosome segregation and genomic stability, crossovers are highly regulated in both frequency and distribution. We previously demonstrated that this strict regulation is not a fatality and that it can be naturally modified (3.6-fold increased frequency and altered distribution) in an allotriploid Brassica hybrid (2n=3x=29; AAC), resulting from a cross between B. napus (2n=4x=38; AACC) and B. rapa (2n=2x=20; AA). Taking advantage of the recently updated Brassica napus genome assembly, which now includes the pericentromeric regions, we unambiguously demonstrated that crossovers occur in these normally cold regions in allotriploids, with the presence of crossovers as close as 375 kb from the centromere. We deciphered that this modified recombination landscape (both frequency and distribution) can be maintained in successive generations of allotriploidy, with even a slight increase of crossover frequency. We also showed that this deregulated meiotic behavior may revert back to a strictly regulated one when recovering an allotetraploid progeny in the second generation. Overall, we provide here for the first time a practical and natural way to switch on and off the tight recombination control in a polyploid crop. We also discuss the potential role of this modified regulation of recombination in polyploid speciation success.

genetics↗

bioRxiv2023

Warnings/Cautions when collecting Brassica diversity along a large climatic gradient

Agriculture faces great challenges to overcome global warming and to improve system sustainability, requiring access to novel genetic diversity. So far, wild populations and local landraces remain poorly explored. This is notably the case for the two diploid species, Brassica oleracea L. (CC, 2n=2x=18) and B. rapa L. (AA, 2n=2x=20). In order to explore genetic diversity in both species, we have collected numerous populations in their center of origin, the Mediterranean basin, on a large contrasting climatic and soil gradient from northern Europe to southern sub-Saharan regions. In these areas, we also collected 14 populations belonging to five B. oleracea closely related species. Before further genetic and agronomic investigations, we controlled the absence of species misidentification using flow cytometry, sequencing of species specific chloroplast genomic region, as well as cytogenetic analyses in case of unexpected results. Looking at the 102 B. oleracea and 146 B. rapa populations showing a good germination among the 112 and 154 populations collected, seventeen populations were misidentified. The most frequent mistake was a confusion of these diploid species with B. napus. Additionally for B. rapa, 2 autotetraploid populations were observed. Habitats of the collected wild populations and landraces are described in our work. This provides a unique plant material characterization that will pave the way for further analyses investigating the genomic regions involved in climatic and microbiota adaptation. This research is supported by the H2020 Prima project BrasExplor.

ecology↗

bioRxiv2023

Genomic relationships among diploid and polyploid species of the genus Ludwigia L. section Jussiaea using a combination of cytogenetic, morphological, and crossing investigations

The genus Ludwigia L. section Jussiaea is composed of a polyploid species complex with 2x, 4x, 6x and 10x ploidy levels, suggesting possible hybrid origins. The aim of the present study is to understand the genomic relationships among diploid and polyploid species in the section Jussiaea. Morphological and cytogenetic observations, controlled crosses, genomic in situ hybridization (GISH), and flow cytometry were used to characterize species, ploidy levels, ploidy patterns, and genomic composition across taxa. Genome sizes obtained were in agreement with the diploid, tetraploid, hexaploid, and decaploid ploidy levels. Results of GISH showed that progenitors of Ludwigia stolonifera (4x) were Ludwigia peploides subsp. montevidensis (2x) and Ludwigia helminthorrhiza (2x), which also participated for one part (2x) to the Ludwigia ascendens genome (4x). Ludwigia grandiflora subsp. hexapetala (10x) resulted from the hybridization between L. stolonifera (4x) and Ludwigia grandiflora subsp. grandiflora (6x). One progenitor of L. grandiflora subsp. grandiflora was identified as L. peploides (2x). Our results suggest the existence of several processes of hybridization, leading to polyploidy, and possibly allopolyploidy, in the section Jussiaea due to the diversity of ploidy levels. The success of GISH opens up the potential for future studies to identify other missing progenitors in Ludwigia L. as well as other taxa.

plant biology↗

bioRxiv2020

Large genomic variants reveal unexplored intraspecific diversity in Brassica rapa genomes

ABSTRACTTraditionally, reference genomes in crop species rely on the assembly of one accession, thus occulting most of intraspecific diversity. However, rearrangements, gene duplications and transposable element content may have a large impact on the genomic structure, which could generate new phenotypic traits. Using two Brassica rapa genomes recently sequenced and assembled using long-read technology and optical mapping, we investigated structural variants and repetitive content between the two accessions and genome size variation among a core collection.We explored the structural consequences of the presence of large repeated sequences in B. rapa ‘Z1’ genome versus the B. rapa ‘Chiifu’ genome, using comparative genomics and cytogenetic approaches. First, we showed that large genomic variants on chromosomes A05, A06, A09 and A10 are due to large insertions and inversions when comparing B. rapa ‘Z1’ and B. rapa ‘Chiifu’ at the origin of important length differences in some chromosomes. For instance, lengths of ‘Z1’ and ‘Chiifu’ A06 chromosomes were estimated in silico to be 55Mb and 29Mb, respectively. To validate these observations, we compared using fluorescent in-situ hybridization (FISH) the two A06 chromosomes present in a F1 hybrid produced by crossing these two varieties. We confirmed a length difference of 17.6% between the A06 chromosomes of ‘Z1’ compared to ‘Chiifu’. Alternatively, using a Copy Number Variation approach, we were able to quantify the presence of a higher number of rDNA and Gypsy elements in ‘Z1’ genome compared to ‘Chiifu’ on different chromosomes including A06. Using flow cytometry, the total genome size of 12 Brassica accessions corresponding to a B. rapa available core collection was estimated and revealed a genome size variation of up to 16% between these accessions as well as some shared inversions.This study revealed the contribution of long-read sequencing of new accessions belonging to different cultigroups of B. rapa and highlighted the potential impact of differential insertion of repeat elements and inversions of large genomic regions in genome size intraspecific variability.Competing Interest StatementThe authors have declared no competing interest.View Full Text

genomics↗