Biology subjects

Mayjonade, B.

Publications and source records attributed to Mayjonade, B..

9 recordsLinked to original sources

bioRxiv2026

Intraspecific variation at the free-living stage of a soil-borne pathogen is organized into an exploration syndrome associated with infectivity

Many pathogens spend a substantial portion of their life cycle outside the host tissues. During its free-living stage, the root legume-plant pathogen Aphanomyces euteiches persists in soil either as non-motile resting oospores or actively explores the environment through mycelium and motile zoospores. These two latter stages are critical for survival, dispersal and host encounter. However, the extent of intraspecific variation during these phases remains poorly explored, and it is still unknown whether they are organized into phenotypic syndromes contributing to infection success. Here, we measured eight free-living phenotypic traits associated with mycelial and zoospore stages across 23 A. euteiches strains from distinct geographic regions (USA, Europe) whose genomes were sequenced. We tested whether traits are organized into a phenotypic syndrome linked to either geographic origin, genomic diversity or infectivity. The microbial strains exhibited substantial intraspecific phenotypic variation that we proposed as an 'exploration syndrome' linked to host search. Beyond this general syndrome, we detected sub-structure according to strains' infectivity, geographic origin and genetic group. This suggests that the free-living stage of pathogens may contribute to disease potential. Our results highlight the importance of integrating functional trait approaches into plant pathology and suggest that the identified "exploration syndrome" may serve as a predictor of infectivity in soilborne oomycete pathogens.

ecology↗

bioRxiv2025

Seasonality, land use, and diversity shape microbiome-pathogen interactions in wild populations of Arabidopsis thaliana

The microbiome often protects plants against pathogens, but most findings are limited to controlled experiments in the lab. In the context of wild populations, one key challenge is to understand sources of variation that impact the commensal microbiome, which in turn shapes the degree of protection. Here, we surveyed both disease symptoms and microbiomes from wild populations of Arabidopsis thaliana over four consecutive seasons (fall/spring) across three different land use types. Land use types varied in the extent of anthropogenic influences and included forest meadows, human-impacted fields adjacent to agriculture or municipal parks, and highly disturbed habitats near railroad tracks. By building an integrative map of abiotic and biotic variables, we find that a key predictor of disease was biodiversity across ecological scales. Plant communities with higher diversity were associated with reduced disease burden in A. thaliana populations but also increased diversity within the microbiome of A. thaliana. This increased microbial diversity was additionally associated with less disease in A. thaliana. However, the diversity-microbiome-disease relationships were all sensitive to season and further modulated by land use. Taken together, our work highlights the importance of anthropogenic change reshaping species interactions across ecological scales to impact disease risk in wild plant populations.

ecology↗

bioRxiv2024

The 1001G+ project: A curated collection of Arabidopsis thaliana long-read genome assemblies to advance plant research

Arabidopsis thaliana was the first plant for which a high-quality genome sequence became available. The publication of the first reference genome sequence almost 25 years ago was already accompanied by genome-wide data on sequence polymorphisms in another accession, or naturally occurring strain. Since then, inventories of genome-wide diversity have been generated at increasingly precise levels. High-density genotype data for A. thaliana, including those from the 1001 Genomes Project, were key to demonstrating the enormous power of GWAS in inbred populations of wild plants, and the comparison of intraspecific polymorphism with interspecific divergence has illuminated many aspects of plant genome evolution. Over the past decade, an increasing number of nearly complete genome sequences have been published for many more accessions. Here, we highlight the diversity of a curated collection of previously published and so far unpublished genome sequences assembled using different types of long reads, including PacBio Continuous Long Reads (CLR), PacBio High Fidelity (HiFi) reads, and Oxford Nanopore Technologies (ONT) reads. This 1001 Genomes Plus (1001G+) resource is being made available at http://1001genomes.org. We invite colleagues with yet unpublished genome assemblies from A. thaliana accessions to contribute to this effort.

genomics↗

bioRxiv2024

The relative effects of abiotic and biotic factors in explaining the structure of soil bacterial communities at diverse taxonomic levels

Soil microbes play pivotal roles in the multifunctioning of terrestrial ecosystems. In the context of global changes, there is an urgent need to protect soil microbial diversity, which relies on determining the abiotic and biotic factors that influence the diversity, composition, and assemblage of soil microbiota. A large number of informative studies have reported edaphic properties and climate factors as key drivers of soil bacteria microbiota. However, these studies were mainly conducted at the phylum level and based on a restricted number of non-microbial variables. In this study, we aimed to estimate the relative effects of abiotic and biotic factors in shaping soil bacterial communities at diverse taxonomic levels by focusing on 160 natural sites located in the southwest of France for which a large and unique set of non-microbial variables is available. After characterizing soil bacterial communities with the highly taxonomically resolving gyrB gene, we identified that in addition to pH, temperature, and precipitations, soil bacterial communities at the lowest taxonomic levels appear strongly structured by soil micronutrients, notably manganese. On the other hand, soil bacterial communities at the highest taxonomic levels appear strongly structured by the interplay between descriptors of plant communities and edaphic properties. Similar to previous observations on microbial pathogens, the strong and positive associations between soil bacterial species and the presence of particular plant species suggest host specificity for soil commensal bacteria. Altogether, a deeper characterization of both abiotic and biotic factors could help fuel programs designed for protecting and restoring soil ecosystem functions.

ecology↗

bioRxiv2022

Unraveling the genetic architecture of the adaptive potential of Arabidopsis thaliana to face the bacterial pathogen Pseudomonas syringae in the context of global change

Phytopathogens are a continuous threat for global food production and security. Emergence or re-emergence of plant pathogens is highly dependent on the environmental conditions affecting pathogen spread and survival. Under climate change, a geographic expansion of pathogen distribution poleward has been observed, potentially resulting in disease outbreaks on crops and wild plants. Therefore, estimating the adaptive potential of plants to novel epidemics and describing its underlying genetic architecture, is a primary need to propose agricultural management strategies reducing pathogen outbreaks and to breed novel plant cultivars adapted to pathogens that might spread in novel habitats under climate change. To address this challenge, we inoculated Pseudomonas syringae strains isolated from Arabidopsis thaliana populations located in south-west of France on the highly genetically polymorphic TOU-A A. thaliana population located east-central France. While no adaptive potential was identified in response to most P. syringae strains, the TOU-A population displays a variable disease response to the P. syringae strain JACO-CL belonging to the phylogroup 7 (PG7). This strain carried a reduced T3SS characteristic of the PG7 as well as flexible genomic traits and potential novel effectors. GWA mapping on 192 TOU-A accessions inoculated with JACO-CL revealed a polygenic architecture. The main QTL region encompasses two R genes and the AT5G18310 gene encoding for ubiquitin hydrolase, a target of the AvrRpt2 P. syringae effector. Altogether, our results pave the way for a better understanding of the genetic and molecular basis of the adaptive potential in an ecologically relevant A. thaliana - P. syringae pathosystem.

pathology↗

bioRxiv2022

Investigating genetic diversity within the most abundant and prevalent non-pathogenic leaf-associated bacteria interacting with Arabidopsis thaliana in natural habitats

Plants interact simultaneously with highly diversified microbes defined as the plant microbiota. Microbiota modulates plant health and appears as a promising lever to develop innovative, sustainable and eco-friendly agro-ecosystems. Key patterns of microbiota assemblages in plants have been revealed by an extensive number of studies based on taxonomic profiling by metabarcoding. However, understanding the functionality of microbiota and identifying the genetic and molecular mechanisms underlying the interplay between plants and their microbiota are still in its infancy and relies on reductionist approaches primarily based on the establishment of representative microbial collections. In Arabidopsis thaliana, most of these microbial collections include one strain per OTU isolated from a limited number of habitats, thereby neglecting the ecological potential of genetic diversity within microbial species to affect the plant-microbiota molecular dialog. With this study, we aimed at estimating the extent of genetic variation between strains within the most abundant and prevalent leaf-associated non-pathogenic bacterial species in 163 natural populations of A. thaliana located south-west of France. By combining a culture-based collection approach consisting of the isolation of more than 7,000 bacterial colonies with an informative-driven approach, we isolated 35 pure strains from eight non-pathogenic bacterial species. We detected significant intra-specific genetic variation at the genomic level and for growth rate in synthetic media. In addition, significant host genetic variation was detected in response to most bacterial strains in in vitro conditions, with the presence of both negative and positive responses on plant growth. Our study provides new genetic and genomic resources for a better understanding of the plant-microbe ecological interactions at the microbiota level. We also highlight the need of considering genetic variation in both non-pathogenic bacterial species and A. thaliana to decipher the genetic and molecular mechanisms involved in the ecologically relevant dialog between hosts and leaf microbiota.

microbiology↗

bioRxiv2022

The genomics of linkage drag in sunflower

Crop wild relatives represent valuable sources of alleles for crop improvement, including adaptation to climate change and emerging diseases. However, introgressions from wild relatives might have deleterious effects on desirable traits, including yield, due to linkage drag. Here we comprehensively analyzed the genomic and phenotypic impacts of wild introgressions into cultivated sunflower to estimate the impacts of linkage drag. First, we generated new reference sequences for seven cultivated and one wild sunflower genotype, as well as improved assemblies for two additional cultivars. Next, relying on previously generated sequences from wild donor species, we identified introgressions in the cultivated reference sequences, as well as the sequence and structural variants they contain. We then used a ridge regression model to test the effects of the introgressions on phenotypic traits in the cultivated sunflower association mapping population. We found that introgression has introduced substantial sequence and structural variation into the cultivated sunflower gene pool, including > 3,000 new genes. While introgressions reduced genetic load at protein-coding sequences and positively affected traits associated with abiotic stress resistance, they mostly had negative impacts on yield and quality traits. Introgressions found at high frequency in the cultivated gene pool had larger effects than low frequency introgressions, suggesting that the former likely were targeted by artificial selection. Also, introgressions from more distantly related species were more likely to be maladaptive than those from the wild progenitor of cultivated sunflower. Thus, pre-breeding efforts should focus, as far as possible, on closely related and fully compatible wild relatives.

genomics↗

bioRxiv2021

APOK3, a pollen killer antidote in Arabidopsis thaliana

According to the principles of heredity, each parental allele of hybrids equally participates in the progeny. At some loci, however, it happens that one allele is favored to the expense of the other. Gamete killers are genetic systems where one allele (the killer) triggers the death of the gametes carrying the other (killed) allele. They have been found in many organisms, and are of major interest to understand mechanisms of evolution and speciation. Gamete killers are particularly prevalent in plants, where they can compromise crop breeding. Here, we deciphered a pollen killer in Arabidopsis thaliana by exploiting natural variation, de novo genomic sequencing and mutants, and analyzing segregations in crosses. We found that the killer allele carries an antidote gene flanked by two elements mandatory for the killing activity. We identified the gene encoding the antidote, a chimeric protein addressed to mitochondria. This gene appeared in the species by association of domains recruited from other genes, and it recently underwent duplications within a highly variable locus, particularly in the killer genotypes. Exploring the species diversity, we identified sequence polymorphisms correlated with the antidote activity.

genetics↗

bioRxiv2018

In situ relationships between microbiota and potential pathobiota in Arabidopsis thaliana

A current challenge in microbial pathogenesis is to identify biological control agents that may prevent and/or limit host invasion by microbial pathogens. In natura, hosts are often infected by multiple pathogens. However, most of the current studies have been performed under laboratory controlled conditions and by taking into account the interaction between a single commensal species and a single pathogenic species. The next step is therefore to explore the relationships between host-microbial communities (microbiota) and microbial members with potential pathogenic behavior (pathobiota) in a realistic ecological context. In the present study, we investigated such relationships within root and leaf associated bacterial communities of 163 ecologically contrasted Arabidopsis thaliana populations sampled across two seasons in South-West of France. In agreement with the theory of the invasion paradox, we observed a significant humped-back relationship between microbiota and pathobiota -diversity that was robust between both seasons and plant organs. In most populations, we also observed a strong dynamics of microbiota composition between seasons. Accordingly, the potential pathobiota composition was explained by combinations of season-specific microbiota OTUs. This result suggests that the potential biomarkers controlling pathogens invasion are highly dynamic.

microbiology↗