Biology subjects

Florez, L.

Publications and source records attributed to Florez, L..

3 recordsLinked to original sources

bioRxiv2026

An effector protein that protects a fungal pathogen from the plant microbiota during host colonisation

Zymoseptoria tritici is the causal agent of Septoria tritici blotch, one of the most economically important wheat diseases worldwide. One of the few cloned wheat resistance genes against Z. tritici, Stb6, recognizes the secreted fungal effector AvrStb6. Although AvrStb6 has been extensively studied as an avirulence determinant, its biological function during host colonization remains unknown. Based on the amphipathic nature of the predicted structure of AvrStb6, we hypothesized the effector to function as a membrane-active antimicrobial protein. However, in vitro growth inhibition assays demonstrated that AvrStb6 does not directly inhibit the growth of wheat-associated bacteria across multiple bacterial genera and experimental conditions. Instead, microbiome analyses of wheat apoplastic fluid revealed shifts in bacterial abundance associated with the presence or absence of AvrStb6 in a susceptible cultivar (without Stb6-induced resistance). This prompted us to further explore other putative microbiome-related functions of AvrStb6. In vitro confrontation assays further showed that deletion of AvrStb6 increased the sensitivity of Z. tritici to antagonistic wheat-associated bacteria, particularly Pseudomonas and Pantoea spp. This phenotype was conserved across independent fungal genetic backgrounds and across virulent and avirulent AvrStb6 variants. Fluorescence-based co-culture assays additionally showed reduced fungal growth and increased bacterial proliferation in the absence of AvrStb6 during interactions with Pseudomonas spp., but not with the control bacterium Escherichia coli. Finally, biochemical assays demonstrated that AvrStb6 associates with the Z. tritici cell wall in vitro, whereas other secreted fungal effectors do not. Collectively, our findings identify a previously uncharacterized role of AvrStb6 in protecting Z. tritici from antagonistic wheat-associated bacteria by associating with the fungal cell wall. More broadly, this work highlights that fungal effectors may contribute to microbial competition and ecological adaptation beyond their established roles in host immune recognition. Author summaryPlant pathogens secrete proteins that help them colonize their hosts. Some of these proteins are recognized by plant immune receptors and trigger disease resistance, but their original biological functions often remain unclear. We investigated the role of AvrStb6, a protein produced by the wheat pathogen that causes Septoria tritici blotch. AvrStb6 is best known because it is recognized by a wheat resistance gene, yet its contribution to fungal growth and survival has remained unknown. We initially tested whether AvrStb6 directly inhibits bacteria that live on wheat leaves, but found no evidence that it acts as an antimicrobial protein. Instead, we discovered that AvrStb6 influences interactions between the pathogen and wheat-associated bacteria. Fungal strains lacking AvrStb6 were more sensitive to several bacterial species that naturally occur in wheat, particularly members of the genera Pseudomonas and Pantoea. We also found that AvrStb6 can associate with the fungal cell wall, suggesting that it helps protect the pathogen during encounters with antagonistic bacteria. Our findings reveal an unexpected role for a fungal effector in microbial competition and show that pathogen proteins traditionally studied in the context of plant immunity can also influence interactions with other microbes. This work highlights the importance of considering the broader microbial community when studying plant-pathogen systems.

pathology↗

bioRxiv2024

Repeated horizontal acquisition of lagriamide-producing symbionts in Lagriinae beetles

Microbial symbionts associate with multicellular organisms on a continuum from facultative associations to mutual codependency. In some of the oldest intracellular symbioses there is exclusive vertical symbiont transmission, and co-diversification of symbiotic partners over millions of years. Such symbionts often undergo genome reduction due to low effective population sizes, frequent population bottlenecks, and reduced purifying selection. Here, we describe multiple independent acquisition events of closely related defensive symbionts followed by genome erosion in a group of Lagriinae beetles. Previous work in Lagria villosa revealed the dominant genome-eroded symbiont of the genus Burkholderia produces the antifungal compound lagriamide and protects the beetles eggs and larvae from antagonistic fungi. Here, we use metagenomics to assemble 11 additional genomes of lagriamide-producing symbionts from seven different host species within Lagriinae from five countries, to unravel the evolutionary history of this symbiotic relationship. In each host species, we detected one dominant genome-eroded Burkholderia symbiont encoding the lagriamide biosynthetic gene cluster (BGC). Surprisingly, however, we did not find evidence for host-symbiont co-diversification, or for a monophyly of the lagriamide-producing symbionts. Instead, our analyses support at least four independent acquisition events of lagriamide-encoding symbionts and subsequent genome erosion in each of these lineages. By contrast, a clade of plant-associated relatives retained large genomes but secondarily lost the lagriamide BGC. In conclusion, our results reveal a dynamic evolutionary history with multiple independent symbiont acquisitions characterized by high degree of specificity. They highlight the importance of the specialized metabolite lagriamide for the establishment and maintenance of this defensive symbiosis.

genomics↗

bioRxiv2018

Representativeness and robustness of TCR repertoire diversity assessment by high-throughput sequencing

High-throughput sequencing (HTS) has the potential to decipher the diversity of T cell repertoires and their dynamics during immune responses. Applied to T cell subsets such as T effector and T regulatory cells, it should help identify novel biomarkers of diseases. However, given the extreme diversity of TCR repertoires, understanding how the sequencing conditions, including cell numbers, biological and technical sampling and sequencing depth, impact the experimental outcome is critical to properly use of these data. Here we assessed the representativeness and robustness of TCR repertoire diversity assessment according to experimental conditions. By comparative analyses of experimental datasets and computer simulations, we found that (i) for small samples, the number of clonotypes recovered is often higher than the number of cells per sample, even after removing the singletons; (ii) high sequencing depth for small samples alters the clonotype distributions, which can be corrected by filtering the datasets using Shannon entropy as a threshold; (iii) a single sequencing run at high depth does not ensure a good coverage of the clonotype richness in highly polyclonal populations, which can be better covered using multiple sequencing. Altogether, our results warrant better understanding and awareness of the limitation of TCR diversity analyses by HTS and justify the development of novel computational tools for improved modelling of the highly complex nature of TCR repertoires.

immunology↗