Biology subjects

Luneau, J. S.

Publications and source records attributed to Luneau, J. S..

4 recordsLinked to original sources

bioRxiv2026

A reproductive hierarchy controls mating fates among sibling yeast gametes

Mating strategies shape inbreeding, gene flow and genetic diversity, yet their outcomes remain challenging to quantify. In Saccharomyces, population-genomic models predict mating predominantly between sibling meiotic products, with rare selfing and outcrossing. Here we developed an integrated framework combining multicolor flow cytometry, time-resolved imaging and mathematical modelling to directly quantify mating across scales. Bulk measurements revealed coexisting strategies whose frequencies vary with density, genotype and environment. A minimal stochastic model uses these population-level patterns to infer probabilistic hierarchies among mating modes, which single-tetrad analyses independently support. These reveal divergent and interdependent reproductive trajectories among sibling gametes, with one pair typically mating first and reshaping opportunities for the others. Temporal heterogeneity in germination and mating further diversifies reproductive outcomes and shapes compatibility, as experimental synchronization overcomes temporal reproductive barriers, enabling hybridization. Together, reproductive strategy emerges from heterogeneous gamete fates, raising the possibility that sibling diversification constitutes reproductive bet-hedging.

genetics↗

bioRxiv2025

Microbes release lower-value metabolites at higher rates

Microbial interactions are shaped by the exchange of metabolites, ranging from intermediates in central carbon metabolism to amino acids, vitamins and fermentation by-products. While specific metabolic processes such as overflow metabolism are well documented, a general principle explaining the chemical diversity of metabolite release and the variation in individual release rates remains elusive. Here, using a combination of computational and experimental approaches on seven different microbes, we show that release rates are negatively correlated with the value of metabolites, and that this relationship explains more variability in release rates than other frequently associated factors. By measuring metabolite release from 67 E. coli mutants lacking individual transport genes, we find that transporters both cause and counteract net metabolite release. These findings suggest that metabolite release constitutes a fitness cost that microbes have evolved to reduce, while revealing the underlying transport mechanism. This unifying explanation reshapes our understanding of how microbial interactions emerge and persist.

microbiology↗

bioRxiv2022

Genome-wide identification of fitness determinants in the Xanthomonas campestris bacterial pathogen during early stages of plant infection

Plant diseases are an important threat to food production. While major pathogenicity determinants required for disease have been extensively studied, less is known on how pathogens thrive during host colonization especially at early infection stages. Here, we used randomly barcoded-transposon insertion site sequencing (RB-TnSeq) to perform a genome-wide screen and identify key bacterial fitness determinants of the vascular pathogen Xanthomonas campestris pv. campestris (Xcc) during infection of the cauliflower host plant (Brassica oleracea). This high-throughput analysis was conducted in hydathodes, the natural entry site of Xcc, in xylem sap and in synthetic media. Xcc did not face a strong bottleneck during hydathode infection. 183 genes important for fitness were identified in plant-associated environments with functional enrichment in genes involved in metabolism when only few genes known to be involved in virulence were found to be affected. The biological relevance of 13 genes was independently confirmed by phenotyping single mutants. Notably, we show that the XC_3388, a protein with no known function (DUF1631), plays a key role in the adaptation and virulence of Xcc possibly through c-di-GMP-mediated regulation. This study thus revealed yet unsuspected social behaviors adopted by Xcc individuals when confined inside hydathodes at early infection stages.

microbiology↗

bioRxiv2021

Xanthomonas transcriptome inside cauliflower hydathodes reveals bacterial virulencestrategies and physiological adaptation at early infection stages

Xanthomonas campestris pv. campestris (Xcc) bacterium is a seed-transmitted vascular pathogen causing black rot disease on cultivated and wild Brassicaceae. Xcc enters the plant tissues preferentially via hydathodes which are organs localized at leaf margins. In order to decipher both physiological and virulence strategies deployed by Xcc during early stages of infection, the transcriptomic profile of Xcc was analyzed three days after entry into cauliflower hydathodes. Despite the absence of visible plant tissue alterations and a bacterial biotrophic lifestyle, 18% of Xcc genes undergo a transcriptional reprogramming, including a striking repression of chemotaxis and motility functions. Xcc full repertoire of virulence factors was not yet activated but the expression of the 95-gene HrpG regulon, including genes coding for the type three secretion machinery important for suppression of plant immunity, was induced. The expression of genes involved in metabolic adaptations such as catabolism of plant compounds, transport functions, sulfur and phosphate metabolism was upregulated while limited stress responses were observed three days post infection. These transcriptomic observations give information about the nutritional and stress status of bacteria during the early biotrophic infection stages and help to decipher the adaptive strategy of Xcc to the hydathode environment.

microbiology↗