Abstract: Trichoderma harzianum Th33 can effectively antagonize many plant pathogenic fungi and has important research and application value. In our previous study, a signal transfer protein Gα gene Thga1 was knocked out from Th33, and the amount of conidiophores and conidia of the knock-out mutant was significantly decreased. Transcriptome sequencing of the Thga1 knockout mutant and Th33 revealed that a total of 29 transcription factors (TFs) were significantly differentially expressed. Among those TFs, a C2H2 transcription factor Tha09974 gene showed the largest differential expression ratio. In this study, Tha09974 was cloned, and Tha09974 knock-out mutant Δ9974 and its reverse mutant R9974 were constructed. The growth and sporulation characters and antagonism against Botrytis cinerea and Fusarium oxysporum of the wild Th33, Δ9974 and R9974 were analyzed. Compared to the wild Th33, the mycelial growth rate of Δ9974 was not significantly different with that of wild type Th33, while the biomass and spore production of Δ9974 decreased by 51.5% and 73.6%, respectively, and the growth inhibition rates against B. cinerea and F. oxysporum decreased by 41.67% and 45.15%, respectively. There was no significant difference in growth rate, biomass, sporulation and the inhibition rate on B. cinerea with R9974 and Th33, but the inhibition rate of R9974 against F. oxysporum was lower than that of the wild strain Th33, while higher than Δ9974. The above results indicated that the expression of Tha09974 was positively regulated by Thga1, and can regulate the growth, sporulation and antagonism of Th33. This study laid the foundation for further revealing the sporulation regulation mechanism of Trichoderma.

Key words: Trichoderma harzianum, transcription factorsTha09974, gene knocking-out, reverse mutation, gene function