Biology subjects

Punt, W.

Publications and source records attributed to Punt, W..

6 recordsLinked to original sources

bioRxiv2026

Bacteria rewire fungal antimicrobial gene expression in microbial arms races

Microbial communities are shaped by antagonistic interactions, yet how competitors evade antimicrobial strategies in a community context remains unclear. Fungi deploy antimicrobial proteins (AMPs) to suppress bacterial niche competitors, but how bacteria counteract these defences is unknown. Here we show that soil microbiota suppress fungal AMP expression, revealing a previously unrecognized mode of intermicrobial interference. In the soil-borne pathogen Verticillium dahliae, AMP genes are highly conserved yet broadly repressed in the presence of natural microbial communities. This repression extends across diverse fungi, suggesting a widespread phenomenon. Correlation analyses of AMP expression and community compositions linked the bacterial genera Leptothrix and Devosia to repression of the V. dahliae AMPs VdL1 and VdD1, respectively. Both AMPs antagonize these bacterial taxa, and microbiota-mediated repression of VdL1 reduces its contribution to fungal soil colonization. Together, our findings reveal that bacteria can evade fungal antagonism by suppressing AMP deployment, highlighting community-level control of microbial competition.

microbiology↗

bioRxiv2025

Differential contributions of an antimicrobial effector from Verticillium dahliae to virulence and tomato microbiota assembly across natural soils

Throughout their life cycle plants associate with diverse and complex microbial communities, known as their microbiota. These microbiota contribute to plant performance and health, in part by providing a microbial barrier against invading plant pathogens. To colonize plant hosts, pathogens not only have to overcome host immune responses, but also breach the microbial barrier, for which they secrete so-called effector proteins. Accordingly, the soil-borne fungal plant pathogen Verticillium dahliae secretes the antimicrobial effector Ave1 to suppress antagonistic microbes and facilitate host colonization. Notably, many pathogens, including V. dahliae, have life stages outside their host plants, for instance in soil, where they encounter diverse microbial communities. Yet, how antimicrobial effectors support establishment across these environments remains poorly understood. To address this, we established a collection of natural soil samples with diverse physicochemical properties and microbiota compositions. Using this collection, we show for three plant species, barley, tomato and cotton, that root-associated bacterial and fungal communities are primarily shaped by the type of soil, whereas the phyllosphere microbiota is mainly determined by plant species. On tomato, we furthermore show that Ave1 differentially contributes to virulence on diverse soils, as Ave1 altered the tomato microbiota on all soils tested, but the taxa affected by these shifts varied depending on the specific soils. Our findings suggest that while Ave1-mediated microbiota manipulation occurs across soils, its impact on fungal virulence is influenced by the specific composition of the soil-derived microbiota assembled by the host.

plant biology↗

bioRxiv2025

Undermining the cry for help: The phytopathogenic fungus Verticillium dahliae secretes an antimicrobial effector protein to undermine host recruitment of antagonistic Pseudomonas bacteria

During pathogen attack, plants recruit beneficial microbes in a "cry for help" to mitigate disease development. Simultaneously, pathogens secrete effectors to promote host colonization through various mechanisms, including targeted host microbiota manipulation. Here, we characterize the Av2 effector of the vascular wilt fungus Verticillium dahliae as a suppressor of the cry for help. Inspired by in silico antimicrobial activity prediction, we investigated the antimicrobial activity of Av2 in vitro. Furthermore, its role in V. dahliae virulence was assessed through microbiota sequencing of inoculated plants, microbial co-cultivation assays, and inoculations in a gnotobiotic plant cultivation system. We show that Av2 inhibits bacterial growth, and acts as a virulence factor during host colonization. Microbiota sequencing revealed involvement of Av2 in suppression of Pseudomonas spp. recruitment upon plant inoculation with V. dahliae, suggesting that Av2 suppresses the cry for help. We show that several Pseudomonas spp. are antagonistic to V. dahliae and sensitive to Av2 treatment. We conclude that V. dahliae secretes Av2 to supress the cry for help by inhibiting the recruitment of antagonistic Pseudomonas spp. to pave the way for successful plant invasion.

plant biology↗

bioRxiv2025

A gnotobiotic system reveals multifunctional effector roles in plant-fungal pathogen dynamics

Plants host diverse microbiota that influence physiological processes and can enhance resilience against invading pathogens that, in turn, evolved effector proteins to manipulate host microbiota in their favor. However, the complexity of microbial communities and their interactions complicates mechanistic research on processes governing microbiota assembly and function. Gnotobiotic systems are valuable tools to study plant microbiota by reducing complexity and enabling controlled microbiota reconstitution experiments. Despite their utility, no gnotobiotic systems have been established to investigate the role of antimicrobial effector proteins in the interactions between plants, their microbiota, and fungal pathogens. Here, we present a refined gnotobiotic system designed to study these interactions, establishing protocols for infections with the fungal pathogen Verticillium dahliae across multiple host plants under sterile conditions. We demonstrate that a synthetic microbial community (SynCom) derived from a culture collection generated for this study can be applied in this system where it interferes with fungal infections. Additionally, using our gnotobiotic system we reveal that specific antimicrobial effectors of V. dahliae, like Ave1L2, contribute to fungal virulence in a microbiota-dependent manner, whereas other antimicrobial effectors, such as Ave1, seem to possess functions beyond microbiota manipulation.

plant biology↗

bioRxiv2023

The soil-borne white root rot pathogen Rosellinia necatrix expresses antimicrobial proteins during host colonization

Rosellinia necatrix is a prevalent soil-borne plant-pathogenic fungus that is the causal agent of white root rot disease in a broad range of host plants. The limited availability of genomic resources for R. necatrix has complicated a thorough understanding of its infection biology. Here, we sequenced nine R. necatrix strains with Oxford Nanopore sequencing technology, and with DNA proximity ligation we generated a gapless assembly of one of the genomes into ten chromosomes. Whereas many filamentous pathogens display a so-called two-speed genome with more dynamic and more conserved compartments, the R. necatrix genome does not display such genome compartmentalization. It has recently been proposed that fungal plant pathogens may employ effectors with antimicrobial activity to manipulate the host microbiota to promote infection. In the predicted secretome of R. necatrix, 26 putative antimicrobial effector proteins were identified, nine of which are expressed during plant colonization. Two of the candidates were tested, both of which were found to possess selective antimicrobial activity. Intriguingly, some of the inhibited bacteria are antagonists of R. necatrix growth in vitro and can alleviate R. necatrix infection on cotton plants. Collectively, our data show that R. necatrix encodes antimicrobials that are expressed during host colonization and that may contribute to modulation of host-associated microbiota to stimulate disease development.

plant biology↗

bioRxiv2021

The Barley HvSTP13GR mutant triggers resistance against biotrophic fungi

High-yielding and stress resistant crops are essential to ensure future food supply. Barley is an important crop to feed livestock and to produce malt, but the annual yield is threatened by pathogen infections. Pathogens can trigger an altered sugar partitioning in the host plant, that possibly leads to an advantage for the pathogen. Hampering these processes represents a promising strategy to potentially increase resistance. We analyzed the response of the barley monosaccharide transporter HvSTP13 towards biotic stress and its potential use for plant protection. The expression of HvSTP13 increased upon bacterial and fungal PAMP application, suggesting a PAMP-triggered signaling that converged on the transcriptional induction of the gene. Promoter studies indicate a region that is likely targeted by transcription factors downstream of PAMP-triggered immunity pathways. We confirmed that the non-functional HvSTP13GR variant confers resistance against an economically relevant biotrophic rust fungus, in barley. In addition, we established targeted CRISPR/Cas9 cytosine base editing in barley protoplasts to generate alternative HvSTP13 mutants and characterized the sugar transport activity and subcellular localization of the proteins. These mutants represent promising variants for future resistance analysis. Our experimental setup provides basal prerequisites to further decode the role of HvSTP13 in response to biological stress. Moreover, in line with other studies, our experiments indicate that the alteration of sugar partitioning pathways, in a host pathogen interaction, is a promising approach to achieve broad and durable resistance in plants.

plant biology↗