Biology subjects

Zamar, R.

Publications and source records attributed to Zamar, R..

4 recordsLinked to original sources

bioRxiv2026

Natural selection acting on the genetics of host response to commensal bacteria

BackgroundMicrobiota members collectively contribute to individual performance in humans, animals, and plants. This led to the quest for probiotics to improve host health and reproductive performance. Although the efficacy of probiotics is known to be strongly affected by environmental factors, microbe-microbe interactions, and microbial strain identity, the effects of host genotype and the underlying genetic architecture have been overlooked. In addition, the evolutionary causes of such genetic variation are typically not addressed. In this study, we aimed to describe the genetic architecture of the adaptation of the host plant Arabidopsis thaliana to commensal bacterial members of its native microbiota by identifying candidate genes associated with fitness proxies and presenting signatures of natural selection. ResultsA Genome-Wide Association study conducted under field conditions revealed extensive variation within a new mapping population of 162 genotypes of A. thaliana scored for total seed production and its two underlying components, namely fruit number and mean seed number per fruit, in response to 13 commensal strains. In agreement with the strong host genotype x commensal strain identity interactions observed for each reproductive trait, the polygenic genetic architecture was highly flexible among the 13 commensal strains. Candidate genes exhibited a significant enrichment in signatures of both local adaptation and balancing selection. In line with the phenotyped reproductive traits, we identified seven candidate genes with functions specifically and strongly linked to seed germination and fertility. ConclusionsOur findings reveal the importance of genotype-by-genotype interactions when measuring fitness proxies on a wild plant species inoculated with key members of its native microbiota. In addition, this study improves our understanding of the genetic signatures of natural selection acting on native host-microbiota adaptive interactions.

evolutionary biology↗

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↗

bioRxiv2023

Genome wide association study of Arabidopsis seed mucilage layers at a regional scale

The myxospermous species Arabidopsis thaliana extrudes a polysaccharidic mucilage from the seed coat epidermis during imbibition. The whole seed mucilage can be divided into a seed-adherent layer and a fully soluble layer, both layers presenting natural genetic variations. The adherent mucilage is variable in size and composition, while the soluble mucilage is variable in composition and physical properties. Studies reporting both the genetic architecture and the putative selective agents acting on this natural genetic variation are scarce. In this study, we set up a Genome Wide Association study (GWAS) based on 424 natural accessions collected from 166 natural populations of A. thaliana located south-west of France and previously characterized for a very important number of abiotic and biotic factors. We identified an extensive genetic variation for both mucilage layers. The adherent mucilage was mainly related to precipitation and temperature whereas the non-adherent mucilage was unrelated to any environmental factors. By combining a hierarchical Bayesian model with a local score approach, we identified 55 and 28 candidate genes, corresponding to 26 and 10 QTLs for the adherent and non-adherent mucilages, respectively. Putative or characterized function and expression data available in the literature were used to filter the candidate genes. Only one gene among our set of candidate genes was already described as a seed mucilage actor, leaving a large set of new candidates putatively implicated inseed mucilage synthesis or release. The present study lay out foundation to understand the influence of regional ecological factors acting on seed mucilage in A. thaliana.

plant biology↗

bioRxiv2022

The genetic architecture of Arabidopsis thaliana in response to native non-pathogenic leaf bacterial species revealed by GWA mapping in field conditions

Non-pathogenic bacteria can largely contribute to plant health by mobilizing and supplying nutrients and by providing protection against pathogens and resistance to abiotic stresses. Yet, the number of GWAS reporting the genetic architecture of the response to individual members of the beneficial microbiota remains limited. In this study, we established a GWAS under field conditions to estimate the level of genetic variation and the underlying genetic architecture, among 162 accessions of Arabidopsis thaliana originating from 54 natural populations located south-west of France, in response to 13 strains of seven of the most abundant and prevalent non-pathogenic bacterial species isolated from the leaf compartment of A. thaliana in the same geographical region. Using a high-throughput phenotyping methodology to score vegetative growth-related traits, extensive genetic variation was detected within our local set of A. thaliana accessions in response to these leaf bacteria, both at the species and strain levels. The presence of crossing reaction norms among strains indicates that declaring a strain as a plant-growth promoting bacterium is highly dependent on the host genotype tested. In line with the strong genotype-by-genotype interactions, we detected a complex and highly flexible genetic architecture between the 13 strains. Finally, the candidate genes underlying the QTLs revealed a significant enrichment in several biological pathways, including cell, secondary metabolism, signalling and transport. Altogether, plant innate immunity appears as a significant source of natural genetic variation in plant-microbiota interactions and opens new avenues for better understanding the ecologically relevant molecular dialog during plant-microbiota interactions.

genetics↗