Small GTPases RasA and RasB regulate development, patulin production, and virulence of Penicillium expansum

Ras GTPases belong to one of the small G proteins, which regulate morphology and growth of filamentous fungi. However, whether Ras GTPases are involved in the biological process of Penicillium expansum remains unclear. In this study, RasA and RasB gene knockout mutants of P. expansum were constructed. ΔPeRasA and ΔPeRasB showed defective growth, insufficient spore development and malformed mycelium. Loss of PeRasA and PeRasB resulted in a markedly reduction of patulin content and a down-regulation genes expression involved in patulin biosynthesis. Deletion of PeRasA and PeRasB significantly down-regulated the expression of MAPK and cAMP signal regulators. Additionally, ΔPeRasA and ΔPeRasB exhibited attenuated virulence on apple and pear fruit and lower gene expression of cell wall degrading enzymes. In summary, PeRasA and PeRasB were involved in the development, patulin synthesis and virulence of P. expansum by controlling MAPK and cAMP signaling pathways.