Comprehensive Analysis of Subtilase Gene Family and Their Responses to Nematode in Trichoderma Harzianum

The subtilase family is the second largest family of serine proteases. Some fungi including Trichoderma species can capture and kill nematodes by secreting hydrolytic enzymes or toxins, among which serine proteases are important enzymes that allow fungi to infect nematodes. Subtilase can degrade nematode and insect body walls. In this study, subtilase family genes were identified from the Trichoderma harzianum genome database, and bioinformatics analysis of the characteristics and evolutionary status of these genes, along with structural and functional analyses of their proteins, was performed. Gene structure analysis revealed that all the 41 subtilase genes contained introns, while some did not have upstream or downstream regions. Chromosome localisation showed that subtilase family members were unevenly distributed in 22 Trichoderma chromosomes, and 3 clusters were present, indicating that they may be hot spots of subtilase genes. Conserved motif analyses showed these proteins contained a commonly conserved motif, and motifs belonging to the same subfamily remained highly similar. The upstream region of the subtilase genes were enriched with different type and numbers of cis-elements, indicating that subtilase genes are likely to play a role in the response to diverse stresses. Transcription of 31 genes was increased after 5 days of infection with nematodes, whereas that of 10 genes decreased. In these subtilase genes, ThSBT4, ThSBT5, ThSBT12, ThSBT27, ThSBT34, ThSBT35, ThSBT38, and ThSBT40 showed significantly upregulated expression with a log2 fold change value of more than 4, and ThSBT35 showed the highest peak. These results laid a theoretical foundation for further research on the function of the subtilase genes and the mechanism of the resistance response.