To identify chitinase genes from the genome of the mycoparasitic Cladosporium sp. strain SYC23, bioinformatical analyses and real-time quantitative PCR (RT-qPCR) were employed to screen mycoparasitism-associated genes at 12, 24, 48, and 72 h post-induction with Aecidium pourthiaea rust spores. A total of eight chitinase genes were identified from SYC23 via bioinformatics analysis and designated CaChi34, CaChi40, CaChi45, CaChi67, CaChi82, CaChi92, CaChi93, and CaChi286 based on sequence and phylogenetic analyses. Analysis of the chitinase protein sequence characteristics revealed molecular weights ranging from 33.86 to 286.03 kDa and theoretical isoelectric points from 4.48 to 7.7. All CaChi genes contained the conserved GH18 domain, and promoter analysis showed that each harbored MYB-binding sites and pathogen-responsive elements. Mycoparasitism-related sequence clustering analysis indicated that the chitinase sequences of SYC23 shared the closest phylogenetic relationship with those from Trichoderma sp. RT-qPCR results following rust spore induction showed that five CaChi genes reached their highest expression levels at 24 h post-induction, CaChi45 was most highly expressed at 72 h post-induction, CaChi93 was continuously upregulated, and CaChi82 was continuously downregulated throughout the induction period. His-tagged recombinant CaChi93 protein was purified from E. coli and characterized. The results demonstrate that the enzymatic activity of CaChi93 was 0.929 U/mg, with optimal reaction conditions at 65 °C and pH 7. Treatment of A. pourthiaea rust spores with the recombinant CaChi93 chitinase confirmed that CaChi93 could effectively dissolve rust spore walls. In conclusion, this study confirms that the mycoparasitic Cladosporium sp. strain SYC23 can secrete chitinase to degrade the rust spore wall and induce spore death, thereby providing novel gene resources and a theoretical basis for the biological control of A. pourthiaea.

The β-1,3-glucanase gene family plays an important role in fungal cell wall degradation and is closely associated with the mycoparasitic interactions of biocontrol fungi. In this study, the β-1,3-glucanase gene family was identified in the mycoparasitic Alternaria alternata strain KMR13, and its expression patterns under Podosphaera pannosa spore induction were analyzed to investigate the role of the gene Aag25 in the degradation of P. pannosa spores. The β-1,3-glucanase gene was extracted from the genome using the bioinformatics method. According to the expression level of spore-induced genes of P. pannosa, the GH17 family genes that may be involved in mycoparasitism were screened, cloned, and expressed. The expressed protein was purified, and its activity and ability to destroy spores of P. pannosa were determined. A total of 30 β-1,3-glucanase genes were identified in strain KMR13, including 18 members of the GH16 family, 8 of the GH17 family, and 2 genes each from the GH64 and GH81 families. Transcriptome analysis revealed that 23 of these genes were expressed under spore induction. Based on differential expression analysis, the β-1,3-glucanase gene Aag25 was selected for prokaryotic expression. The recombinant Aag25 protein (~32.08 kDa) was successfully induced and purified, exhibiting an enzymatic activity of 1.464 U/mg protein. Functional assays demonstrated that recombinant Aag25 could effectively disrupt the cell walls of P. pannosa spores, leading to spore rupture and cytoplasmic leakage. These results indicate that Aag25 plays an important role in fungal cell wall degradation during the mycoparasitic process of strain KMR13 and provides a potential enzymatic resource for the development of biological control strategies targeting fungal pathogens.