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POSTERS: Late Breaking II

P-658 - Functional analysis of secreted proteins in the mycoparasitic fungus Hansfordia pulvinata

Tuesday, August 5, 2025
10:15 AM - 11:00 AM HST
Location: Exhibit Hall 3
Abstract Text: Cladosporium fulvum (syn. Fulvia fulva) is a biotrophic fungal pathogen that causes leaf mold of tomato. The fungus enters leaves through stomata and colonizes the apoplastic space. C. fulvum frequently evolves new races that overcome resistant tomato cultivars. Coincidentally, we discovered that the mycoparasitic fungus Hansfordia pulvinata overgrows C. fulvum lesions, resulting in suppressed disease progression on these leaves. To elucidate the molecular basis of the tripartite interaction among tomato, C. fulvum and H. pulvinata, we performed the RNA-seq transcriptome analysis under in vitro and on planta mycoparasitic conditions. In H. pulvinata, a total of 165 genes encoding predicted secreted proteins were highly expressed under both conditions. In this study, we focused on two genes: HpNlp1 and HpRit1 genes, which are homologous to virulence factors reported in plant pathogens. Nep1-like proteins (NLPs), conserved across bacteria, fungi, and oomycetes, are known to disrupt plant plasma membranes. Purified HpNlp1 protein did not directly inhibit the spore germination or hyphal elongation of C. fulvum, but it did induce the accumulation of antifungal compounds against C. fulvum in the plant apoplast. HpRit1 encodes ribonuclease T2 and contains the CASI and CASII domains required for enzymatic activity. It was localized in the cytoplasm of C. fulvum. Therefore, HpRit1 was expected to degrade RNA in the host fungus. These results suggest that the two secreted proteins in H. pulvinata have functions that have adapted to its mycoparasitic lifestyle.