Gα3 subunit Thga3 positively regulates conidiation, mycoparasitism, chitinase activity, and hydrophobicity of Trichoderma harzianum

Abstract Heterotrimeric G-proteins are key elements of signal transduction pathways, which participate in regulating multiple biological processes in fungi including growth, conidiation, antagonism, and mycoparasitism. Among G protein subunits, Gα3 showed diverse regulatory functions in different fungi. In this study, we cloned a Gα3 subunit coding gene thga3 from T. harzianum Th33 that can antagonize Rhizoctonia solani and some other plant pathogenic fungi. A thga3 deletion strain Δ thga3 was generated using the double-crossover homologous recombination strategy, and R thga3 was generated by transforming thga3 -expressing vector into the protoplasts of Δ thga3 by the PEG/CaCl 2 -mediated method. The biological characteristics of wild-type Th33, Δ thga3 and R thga3 were evaluated. Compared with wild-type Th33, Δ thga3 showed 15%, 94%, and 23% decrease in hyphal growth, conidia yield, and chitinase activity, respectively, and Δ thga3 showed lower antagonistic and mycoparasitism abilities, while there were no significant differences between wild-type Th33 and R thga3 . The hyphal surface hydrophobicity of Δ thga3 significantly decreased compared with those of the wild-type Th33 and R thga3 . qRT-PCR analysis revealed that transcript abundance of the hydrophobin gene (tha_09745) of Δ thga3 decreased by 80% compared with that of wild-type Th33 and R thga3 . The results showed that thga3 positively regulates the growth, conidiation, hydrophobicity, chitinase activities, and mycoparasitism of Th33 towards R. solani . We hence deduced that the expression level of Tha_09745 is correlated to the hyphal hydrophobicity of Th33 and therefore affects the other biological characteristics of Th33. The findings of this report provide a foundation for elucidating the G-protein signal regulatory mechanisms of fungi.