PdGpaA controls the growth and virulence of Penicillium digitatum by regulating cell wall reorganization, energy metabolism, and CDWEs production

Abstract

Penicillium digitatum could infect citrus and cause devastating green mold disease. One of the essential parts of the G protein is the Gα subunit, which is essential to signal transduction in filamentous fungi but has not been reported in P. digitatum. In this study, PdGpaA was identified as a homolog of Gα in P. digitatum, and deletion of the PdGpaA gene significantly accelerated early-stage spore germination and inhibited late-stage hyphal growth and conidiophore formation. The ΔPdGpaA strain showed faster growth in sodium dodecyl sulfate (SDS) and calcofluor white (CFW) but more sensitivity to Congo red (CR). We predicted that cell wall integrity had been compromised due to cell wall rearrangement. Moreover, the increased quantity of septa and the reorganization of cell walls were confirmed by CFW staining and quantitative real-time PCR analysis. Deletion of the PdGpaA gene increased intracellular reactive oxygen species (ROS)and mitochondrial deterioration, which obstruct the TCA cycle and hinder energy metabolism. A pathogenicity test revealed that the lesion diameter was decreased by 90.62 % in the ΔPdGpaA strain, probably as the result of a decline in the activity of pectinase and cellulase. In addition, the ΔPdGpaA strain was more sensitive to prochloraz, KCl and H2O2. In conclusion, this study provides multiple functions for the PdGpaA gene, which might have broad application space and prospects in the control of citrus green mold.