Project description:Positive and negative ecological interactions shape the dynamics and composition of natural microbial communities. The mechanisms behind microbe-microbe interactions, particularly those protein-based, are not well understood and only a small percentage of such interactions has been studied. We hypothesize that secreted proteins are a powerful and highly specific toolset to shape and defend a favorable plant niche. Here, we have studied Albugo candida, an obligate plant parasite from the protist Oomycota phylum, for its potential to inhibit and promote the growth of bacteria through secretion of proteins into the apoplast. Amplicon sequencing and network analysis of Albugo-infected and uninfected samples revealed an abundance of negative correlations between Albugo and other phyllosphere microbes. Analysis of the secreted proteome of Albugo candida combined with machine-learning predictors enabled the selection of candidates for heterologous expression and study of their inhibitory activity in vitro. We found that three of the candidate proteins showed a selective antimicrobial activity on several gram-positive bacterial strains isolated from Arabidopsis thaliana. We could ascribe the antibacterial activity of the candidates to their intrinsically disordered regions and positively correlate it with their net charge. This is the first report of protist proteins that have an antimicrobial activity under apoplastic conditions and therefore are potential biocontrol tools for a targeted manipulation of the microbiome.
Project description:Infection by Albugo species, resulting in white rust disease, suppresses host plant immunity, and can even enable Albugo laibachii-infected Arabidopsis to support growth and reproduction of the non-host potato late blight pathogen Phytophthora infestans. However, the mechanisms involved in non-host resistance remain to be elucidated. Here, we investigate specific host defense mechanisms that are suppressed by A. laibachii and A. candida infection, and compare the resistance contributed by indole glucosinolates and camalexin to that resulting from other components of defense induced by salicylic acid. We conclude a broad repertoire of host defense components contributes to non-host resistance in Arabidopsis to P. infestans, with a particular role for tryptophan-derived anti-microbial metabolites. Identifying the mechanisms involved in non-host resistance to pathogens such as P. infestans is necessary in the development of strategies to ensure future food security.
Project description:Candida lusitaniae is an emerging human opportunistic yeast, which can switch from yeast to pseudohyphae, and one of the rare Candida species capable of sexual reproduction. Its haploid genome and the genetic tools available make it a model of interest to study gene function. This study describes the consequences of DPP3 inactivation on cell morphology and mating, both altered in the dpp3Δ knock-out. Interestingly, reintroducing a wild-type copy of the DPP3 gene in the dpp3Δ mutant failed to restore the wild-type phenotypes. Proteomic analyses showed that about 150 proteins were statistically deregulated in the dpp3Δ mutant, and that most of them did not return to their wild-type level in the reconstituted DPP3 strain. The analysis of the segregation of the dpp3Δ mutation and the phenotypes in the progeny of a cross (between the dpp3Δ knock-out and a wild-type strain) showed that the phenotypes are not linked to dpp3Δ, but to a secondary mutation. Genome sequencing of the dpp3Δ mutant allowed us to identify this secondary mutation.
