cpubi4 Is Essential for Development and Virulence in Chestnut Blight Fungus

Abstract

Ubiquitination plays key roles in eukaryotic growth, stress adaptation, and metabolic regulation. In our previous work, ubiquitin was found to be secreted in the hypovirus-infected strain of Cryphonectria parasitica, a phytopathogenic filamentous fungus responsible for the chestnut blight. Here we report the functional and molecular characterization of a polyubiquitin gene, cpubi4, in C. parasitica. The expression of cpubi4 was upregulated by the infection of a hypovirus. Deletion of cpubi4 resulted in abnormal morphology, reduced sporulation, attenuation of virulence, and significant reduction in ubiquitination. A total of 378 sites in 236 proteins were identified to be significantly decreased in ubiquitination in the absence of cpubi4. Quantitative proteome analysis revealed that 285 in 4,776 identified proteins changed in abundance (1.5-fold, P < 0.05) in the cpubi4 null mutant, as compared with the wild-type strain.

The Polyubiquitin Gene MrUBI4 Is Required for Conidiation, Conidial Germination, and Stress Tolerance in the Filamentous Fungus Metarhizium robertsii

“…The polyubiquitin gene in fungi has been reported to be involved in stress responses such as heat stress [6,14,16,17]. Consistent with previous studies in yeast, C. albicans , and C. parasitica [6,17,18], the MrUBI4 mutant showed decreased resistance to high temperatures when compared to control strains. Previously, we found that the ubiquitin-proteasome pathway was significantly induced by heat stress in M. robertsii [28].…”

“…Furthermore, the conidiation assays showed that the conidia yield in ∆MrUBI4 was significantly reduced when compared to the control. Significantly reduced conidia yields were also observed in the polyubiquitin gene-deletion strains of M. oryzae [12] and cpubi4 (homolog gene of yeast UBI4 )-deletion strains of C. parasitica [18]. Accordingly, our qPCR results showed that the transcript levels of several conidiation-related genes, including brlA , abaA , wetA , and flbD , were significantly decreased in ∆MrUBI4 , thus indicating that MrUBI4 might be involved in the regulation of asexual sporulation.…”

“…Previously, polyubiquitin gene expression at the transcription level was observed to be significantly upregulated under environmental stress in different pathogenic fungi [13,14,15]. Subsequently, many polyubiquitin genes have been functionally characterized via gene deletion in several fungi including S. cerevisiae [6,11,16]; the human pathogen, Candida albicans [17]; and the plant pathogenic fungi, Magnaporthe oryzae and Cryphonectria parasitica [12,18]. For example, deletion of the yeast polyubiquitin gene UBI4 resulted in reduced resistance to stresses such as high temperature and oxidative stress [6,11,16].…”

“…Inactivation of UBI4 also affected fungal growth and stress resistance in the human pathogen, C. albicans [17]. Furthermore, disruption of the polyubiquitin gene resulted in defective development and pathogenicity in M. oryzae and C. parasitica [12,18]. However, it is unclear whether the polyubiquitin gene is required for fungal development, stress tolerance, and virulence in entomopathogenic fungi such as Metarhizium robertsii .…”

Comparative Genomic Data Provide New Insight on the Evolution of Pathogenicity in Sporothrix Species

“…Hsp70 functioned as a stress-related transcriptional co-activator is required for fungal virulence ( Weissman et al, 2020 ). Deletion of ubiquitin genes results in abnormal morphology, reduced sporulation, and attenuation of virulence ( Oh et al, 2012 ; Chen et al, 2018 ). SOD contributes to the growth and survival under conditions of oxidative stress ( Poli et al, 2004 ), and the antioxidant function of Cu SOD has been reported to be critical for the pathogenesis of fungi ( Narasipura et al, 2003 ).…”