Biology subjects

Petti, G.

Publications and source records attributed to Petti, G..

6 recordsLinked to original sources

bioRxiv2026

Structural homology reveals cerato-platanins as conserved antimicrobials repeatedly co-opted for fungal host colonization

Fungal cerato-platanins (CPs) are small ([~]12 kDa) secreted proteins broadly conserved across filamentous fungi and implicated in a striking diversity of biological processes, ranging from fungal development to interactions with plant hosts. However, a core molecular activity unifying these diverse functions has remained elusive. Fungal pathogens secrete effector proteins, including CPs, to manipulate host physiology and promote colonization. Increasing evidence demonstrates that particular fungal effectors possess antimicrobial activity that enables pathogens to reshape host-associated microbiota during infection, and that antimicrobial activity is strongly enriched among evolutionarily conserved secreted proteins. These findings suggests that intermicrobial competition represents an ancient and fundamental fungal trait, and that several effectors that manipulate plant hosts evolved from ancient antimicrobials. Here, we identify antimicrobial activity as the conserved core function of the CP family, from which diverse roles in environmental adaptation and host interaction evolved. Structural analysis of the Verticillium dahliae secretome identified a structural cluster containing the CP protein CP1 and the previously characterized antimicrobial effector Ave1, providing the first structural link between CPs and antimicrobial activity. Accordingly, functional assays demonstrate that V. dahliae CPs exhibit selective antimicrobial activity in vitro. Expanding this analysis to a wide diversity of phylogenetic lineages and ecological lifestyles revealed that antimicrobial features are broadly conserved across the CP family. Together, our findings identify antimicrobial activity as an ancient and conserved molecular function that unifies the CP family and support a model in which host-manipulating effector functions evolved from ancestral proteins that mediate inter-microbial competition.

microbiology↗

bioRxiv2026

A fungal pathogen effector that shapes host plant microbiota kills bacteria through lipoteichoic acid binding and membrane disruption

Antimicrobial proteins are ancient and widespread molecules that contribute to survival across all domains of life. We previously showed that fungal plant pathogens secrete antimicrobial proteins to suppress antagonistic members of the host microbiota and thereby promote host colonization. The soil-borne plant pathogen Verticillium dahliae employs the bactericidal protein VdAve1 for this purpose. Here, we elucidate the mode of action of VdAve1 and define its mechanism as a distinct type of antimicrobial activity. Nuclear magnetic resonance (NMR) analysis revealed that VdAve1 adopts a jelly-roll barrel-like fold. Functionally, VdAve1 disrupts bacterial plasma membranes, and synthetic peptides derived from its positively charged regions retain antimicrobial activity, indicating that these regions contribute to its function. We further show that the bacterial model system Bacillus subtilis responds to VdAve1 by modifying teichoic acids, and that loss of these modifications increases bacterial sensitivity. Consistent with this, VdAve1 binds lipoteichoic acid (LTA), a major component of the Gram-positive cell wall. Together, our findings support a model in which VdAve1 binds LTA to localize at the bacterial surface, where it perturbs the plasma membrane, leading to membrane collapse and cell death. SIGNIFICANCE STATEMENTPlant-pathogenic microbes secrete effector proteins to promote host colonization. While these proteins are typically studied for their roles in host manipulation, some affect host-associated microbial communities by exhibiting antimicrobial activity. However, their modes of action remain largely unexplored. The fungal plant pathogen Verticillium dahliae secretes the antimicrobial effector VdAve1 to inhibit bacterial antagonists in the host microbiota. Here, we characterize the mode of action of VdAve1. We show that VdAve1 binds lipoteichoic acid, a major component of the cell wall of Gram-positive bacteria. This promotes VdAve1 accumulation close to the plasma membrane, and through electrostatic interactions it disrupts the plasma membrane. We further determine VdAve1 structure by NMR, revealing VdAve1 adopts a {beta}-barrel-like fold. Together, our findings show the mechanism by which a fungal effector inhibits bacterial growth and thereby how it may influence host-associated bacterial communities.

microbiology↗

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

An ancient antimicrobial protein co-opted by a fungal plant pathogen for in planta mycobiome manipulation

Microbes typically secrete a plethora of molecules to promote niche colonization. Soil-dwelling microbes are well-known producers of antimicrobials that are exploited to outcompete microbial co-inhabitants. Also plant pathogenic microbes secrete a diversity of molecules into their environment for niche establishment. Upon plant colonization, microbial pathogens secrete so-called effector proteins that promote disease development. While such effectors are typically considered to exclusively act through direct host manipulation, we recently reported that the soil-borne fungal xylem-colonizing vascular wilt pathogen Verticillium dahliae exploits effector proteins with antibacterial properties to promote host colonization through the manipulation of beneficial host microbiota. Since fungal evolution preceded land plant evolution, we now speculate that a subset of the pathogen effectors involved in host microbiota manipulation evolved from ancient antimicrobial proteins of terrestrial fungal ancestors that served in microbial competition prior to the evolution of plant pathogenicity. Here, we show that V. dahliae has co-opted an ancient antimicrobial protein as effector, named VdAMP3, for mycobiome manipulation in planta. We show that VdAMP3 is specifically expressed to ward off fungal niche competitors during resting structure formation in senescing mesophyll tissues. Our findings indicate that effector-mediated microbiome manipulation by plant pathogenic microbes extends beyond bacteria and also concerns eukaryotic members of the plant microbiome. Finally, we demonstrate that fungal pathogens can exploit plant microbiome-manipulating effectors in a life-stage specific manner, and that a subset of these effectors has evolved from ancient antimicrobial proteins of fungal ancestors that likely originally functioned in manipulation of terrestrial biota. SIGNIFICANCE STATEMENTMicrobes secrete a diversity of molecules into their environment to mediate niche colonization. During host ingress, plant pathogenic microbes secrete effector proteins that facilitate disease development, many of which deregulate host immune responses. We recently demonstrated that plant pathogens additionally exploit effectors with antibacterial activities to manipulate beneficial plant microbiota to promote host colonization. Here, we show that the fungal pathogen Verticillium dahliae has co-opted an ancient antimicrobial protein, that likely served in microbial competition in terrestrial environments before land plants existed, as effector for the manipulation of fungal competitors during host colonization. Thus, we demonstrate that pathogen effector repertoires comprise antifungal proteins, and speculate such effectors could be exploited for the development of novel antimycotics.

microbiology↗

bioRxiv2020

A plant pathogen utilizes effector proteins for microbiome manipulation

During colonization of their hosts, pathogens secrete effector proteins to promote disease development through various mechanisms. Increasing evidence shows that the host microbiome plays a crucial role in health, and that hosts actively shape their microbiomes to suppress disease. We hypothesized that pathogens evolved to manipulate host microbiomes to their advantage in turn. Here, we show that the fungal plant pathogen Verticillium dahliae utilizes effector proteins for niche colonization through selective manipulation of host microbiomes by suppressing microbes with antagonistic activities. Moreover, we show that effector proteins are similarly exploited for microbiome manipulation in the soil environment, where the fungus resides in absence of a host. In conclusion, we demonstrate that pathogens utilize effector proteins to modulate microbiome compositions and propose that their effector catalogs represent an untapped resource for novel antibiotics.

microbiology↗