Biology subjects

Sarthou, A.-S.

Publications and source records attributed to Sarthou, A.-S..

4 recordsLinked to original sources

bioRxiv2026

Leaf hydraulics is a core component of plant immunity

Hydathodes at leaf margins mediate guttation of xylem-derived fluids and serve as primary entry sites for adapted vascular bacterial pathogens such as Xanthomonas campestris. Infection of Arabidopsis mutants with fewer hydathodes resulted in spontaneous mesophyll water-soaking and revealed unexpectedly-large pathogen populations explained by direct infection of the mesophyll niche through stomata and subsequent proliferation. Physical blockage of hydathodes also induced mesophyll water-soaking and enhanced bacterial growth in both Arabidopsis and cauliflower leaves. These findings reveal a dual role for hydathodes as primary sites of infection while being essential to restrict pathogen proliferation in nonvascular tissues. More broadly, our study identifies leaf hydraulics and guttation as central components of water immunity in vascular plants.

plant biology↗

bioRxiv2026

Genetic coupling of hydathode formation with leaf morphogenesis maintains water homeostasis

Hydathodes are specialized leaf structures present across vascular plants that allow guttation by connecting the xylem to the external environment through epithem tissue and permanently open water pores. However, the genetic mechanisms controlling their formation and physiological roles remain poorly understood. Here, we identify a genetic regulatory network that controls hydathode formation and links this process to leaf morphogenesis. This network converges on auxin signaling to coordinate the formation of the three hydathode cell types. We further show that epithem development requires sustained cell proliferation with limited endoreduplication. Analysis of hydathode mutants demonstrates that hydathode size and number are required to prevent reversible leaf flooding. Together, these findings establish a genetic framework for hydathode morphogenesis and uncover a central role for hydathodes in maintaining leaf water homeostasis under fluctuating environmental conditions.

plant biology↗

bioRxiv2024

Developmental rewiring of the NGAL/CUC/KLU network associated with pleiotropic roles of NGAL genes

Gene Regulatory Networks (GRNs) play prominent roles in regulating developmental processes, and their modulation across species is a major source for evolutionary innovation. However, it remains poorly understood how GRNs are rewired between different organs within a single species. This question is particularly relevant for pleiotropic genes, which may exhibit organ-specific GRN modulations potentially reflecting their diverse functions. To address this, we investigated the NGATHA-like (NGAL) genes, as a model for pleiotropic genes that regulate growth or patterning in multiple Arabidopsis organs via two distinct pathways involving the CUP-SHAPED COTYLEDON (CUC) and KLUH (KLU) genes. By combining genetic analysis with gene expression characterization, we uncovered significant organ-specific rewiring of the NGAL/CUC/KLU regulatory module. Our findings highlight that changes in gene expression patterns, potentially arising from developmental constraints, play a pivotal role in the organ-specific modulation of GRNs. Furthermore, GRNs at the molecular and functional levels do not always align perfectly, potentially due to the influence of additional regulatory mechanisms. Altogether, our findings reveal significant modulation of the GRNs associated with pleiotropic genes. We propose that this flexibility in GRNs facilitates gene pleiotropy.

plant biology↗

bioRxiv2018

Viral metagenomic analysis of the cheese surface: a comparative study of rapid procedures for extracting virus-like particles

The structure and functioning of microbial communities from fermented foods, including cheese, have been extensively studied during the past decade. However, there is still a lack of information about both the occurrence and the role of viruses in modulating the function of this type of spatially structured and solid ecosystems. Viral metagenomics was recently applied to a wide variety of environmental samples and standardized procedures for recovering virus-like particles from different type of materials has emerged. In this study, we adapted a procedure originally developed to extract viruses from fecal samples, in order to enable efficient virome analysis of cheese surface. We tested and validated the positive impact of both addition of a filtration step prior to virus concentration and substitution of purification by density gradient ultracentrifugation by a simple chloroform treatment to eliminate membrane vesicles. Viral DNA extracted from the several procedures, as well as a vesicle sample, were sequenced using Illumina paired-end MiSeq technology and the subsequent clusters assembled from the virome were analyzed to assess those belonging to putative phages, plasmid-derived DNA, or even from bacterial chromosomal DNA. The best procedure was then chosen, and used to describe the Epoisses cheese virome. This study provides the basis of future investigations regarding the ecological importance of viruses in cheese microbial ecosystems.\n\nIMPORTANCEWhether bacterial viruses (phages) are necessary or not to maintain food ecosystem function is not clear. They could play a negative role by killing cornerstone species that are necessary for fermentation. But they might also be positive players, by preventing the overgrowth of unwanted species (e.g. food spoilers). To assess phages contribution to food ecosystem functioning, it is essential to set up efficient procedures for extracting viral particles in solid food matrix, then selectively sequence their DNA without being contaminated by bacterial DNA, and finally to find strategies to assemble their genome out of metagenomic sequences. This study, using cheese rind surface as a model, describes a comparative analysis of procedures for selectively extracting viral DNA from cheese and to efficiently characterize the genome of dominant phages with cross-sample assembly.

microbiology↗