Grape white rot is a destructive fungal disease occurring worldwide.  Recently, Coniella vitis was identified as the predominant pathogen causing this disease in China.  As the periderms of grape shoots are severely degraded by C. vitis, it was speculated that cell wall-degrading enzymes (CWDEs) might play a key role in the pathogenesis of this disease.  Therefore, this study aimed to examine the hydrolytic activity of the CWDEs of C. vitis.  The results showed that xylanase (Xy) and xyloglucanase (XEG) had high levels of hydrolytic activity both in vitro and in vivo.  Furthermore, a high-virulence fungal strain exhibited higher levels of Xy and XEG activities compared with a low-virulence strain.  The genome of the fungus was found to harbor two XEG-coding genes CvGH74A and CvGH74B, which belonged to the glycoside hydrolase (GH)74 family.  The expression level of CvGH74A was found to be high during pathogen infection.  CvGH74A gene deletion mutants were generated using the split-marker method.  The deletion of CvGH74A decreased both the hydrolytic activities of XEG and Xy and also the ability of the fungus to infect the grape leaves.  No differences in the hyphal growth, morphology of colonies, or conidiation were found between the ΔCvGH74A mutant strains and the wild-type strain.  Together, these results suggested that CvGH74A acted as an important virulence factor, and its enzymatic activity might regulate the virulence of the pathogen.  This study was novel in reporting that GH74 XEG acted as a virulence factor in C. vitis.

FgGCN5, a GCN5 homolog in Fusarium graminearum, plays a critical role in hyphal vegetative growth, asexual and sexual reproduction, deoxynivalenol (DON) biosynthesis and plant infection.  For nuclear localized GCN5, four conserved sequence motifs (I–IV) are presented in the catalytic domain and a bromodomain in the carboxy-terminus.  As a lysine acetyltransferase, conserved negatively charged residues are present to neutralize the protons from lysine substrates.  However, the role of conserved motifs/domains and residues in FgGCN5 are unclear.  Here, we generated deletion mutant strains for each the conserved motifs/domains and a glutamate residue 130 (E130) replacement mutant.  Deletion of each conserved motif in the catalytic domain and replacement of E130 site resulted in manifold defects in hyphae growth, asexual and sexual development, DON biosynthesis, and plant infection.  Phenotypic defects in the mutant strains were similar to deletion mutants.  The deletion of the bromodomain led a significant reduction in DON production and virulence, with no effects on hyphae growth, asexual or sexual reproduction.  FgGCN5 was further found to localize to the nucleus in conidia and hyphae cells.  In conclusion, FgGCN5 encodes a nuclear localized acetyltransferase.  The conserved motifs in the catalytic domain and E130 are essential for correct functions of the gene.  The conserved bromodomain is important for DON production and pathogen virulence.  This was the first report to identify the functions of conserved motifs/domains in FgGCN5, which will contribute to our understanding of the mechanism(s) by which FgGCN5 regulates F. graminearum.