Functions of thga1 Gene in Trichoderma harzianum Based on Transcriptome Analysis

Trichoderma spp. are important biocontrol filamentous fungi, which are widely used for their adaptability, broad antimicrobial spectrum, and various antagonistic mechanisms. In our previous studies, we cloned thga1 gene encoding GαI protein from Trichoderma harzianum Th-33. Its knockout mutant showed that the growth rate, conidial yield, cAMP level, antagonistic action, and hydrophobicity decreased. Therefore, Illumina RNA-seq technology (RNA-seq) was used to determine transcriptomic differences between the wild-type strain and thga1 mutant. A total of 888 genes were identified as differentially expressed genes (DEGs), including 427 upregulated and 461 downregulated genes. All DEGs were assigned to KEGG pathway databases, and 318 genes were annotated in 184 individual pathways. KEGG analysis revealed that these unigenes were significantly enriched in metabolism and degradation pathways. GO analysis suggested that the majority of DEGs were associated with catalytic activities and metabolism processes that encode carbohydrate-active enzymes, secondary metabolites, secreted proteins, or transcription factors. According to the functional annotation of these DEGs by KOG, the most abundant group was "secondary metabolite biosynthesis, transport, and catabolism." Further studies for functional characterization of candidate genes and pathways reported in this paper are necessary to further define the G protein signaling system in T. harzianum.