ArfA and SarA small GTPases involved in growth, patulin biosynthesis and virulence of Penicillium expansum

Although the Sar/Arf GTPase belonging to a small family of GTPases contributes to growth of fungi, its function in postharvest fungi has not been characterized. Here, ArfA and SarA gene deletion mutants were generated in Penicillium expansum. We found that ΔArfA and ΔSarA exhibited attenuated colony growth and rough colony morphology, as well as insufficient spore development. ΔArfA also increased hyphal branches. Stress experiments showed that knocking out the ArfA or SarA genes affected cell wall integrity of the P. expansum strain. In addition, ΔArfA and ΔSarA significantly downregulated the expression of genes controlling spore development (wetA, abaA and brlA) and MAPK pathway regulators (Fus3, Kss1, Hog1 and Mpk1). Absence of ArfA and SarA reduced patulin production, and the related gene expression was significantly limited. ΔArfA showed attenuated virulence in infected fruit and downregulated PG and PL gene expression. However, ΔSarA had no significant effect on fungal virulence. Taken together, both ArfA and SarA contribute to the growth, development and patulin biosynthesis in P. expansum. ArfA is also involved in the virulence of P. expansum in fruit.