Unveiling the Secretome of the Fungal Plant Pathogen Neofusicoccum parvum Induced by In Vitro Host Mimicry

Abstract

<i>Neofusicoccum parvum</i> is a fungal plant pathogen of a wide range of hosts but knowledge about the virulence factors of <i>N. parvum</i> and host-pathogen interactions is rather limited. The molecules involved in the interaction between <i>N. parvum</i> and <i>Eucalyptus</i> are mostly unknown, so we used a multi-omics approach to understand pathogen-host interactions. We present the first comprehensive characterization of the <i>in vitro</i> secretome of <i>N. parvum</i> and a prediction of protein-protein interactions using a dry-lab non-targeted interactomics strategy. We used LC-MS to identify <i>N. parvum</i> protein profiles, resulting in the identification of over 400 proteins, from which 117 had a different abundance in the presence of the <i>Eucalyptus</i> stem. Most of the more abundant proteins under host mimicry are involved in plant cell wall degradation (targeting pectin and hemicellulose) consistent with pathogen growth on a plant host. Other proteins identified are involved in adhesion to host tissues, penetration, pathogenesis, or reactive oxygen species generation, involving ribonuclease/ribotoxin domains, putative ricin B lectins, and necrosis elicitors. The overexpression of chitosan synthesis proteins during interaction with the <i>Eucalyptus</i> stem reinforces the hypothesis of an infection strategy involving pathogen masking to avoid host defenses. <i>Neofusicoccum parvum</i> has the molecular apparatus to colonize the host but also actively feed on its living cells and induce necrosis suggesting that this species has a hemibiotrophic lifestyle.