Precocious sexual inducer (psi)-producing oxygenases (Ppos) participate in the production of C8 moldy volatile compounds (MVOCs), and these compounds could act as signal molecules modulating G protein signaling cascades, which participates in the growth and development, secondary metabolisms and pathogenicity of filamentous fungi. In this study, PePpoA and PePpoC proteins were identified in Penicillium expansum. The deletion of ppoA decreased C8 MVOC production in P. expansum, while they were not detected in the ΔppoC strain (p < 0.05). In addition, down-regulated cAMP/PKA and PKC/PLC signaling showed in the two mutants (p < 0.05). The two mutants showed slow colony growth and down-regulated expression of genes regulating spore development (abaA, wetA, brlA and vosA) with broken morphology of spore and hyphae. In addition, the two mutants had decreased pathogenicity on apple fruit and less patulin production in vitro and in vivo. Compared with ΔppoA strain, the deletion of ppoC inhibited G protein signaling pathways more, and the ΔppoC strain had more defective growth and development as well as reduced pathogenicity and patulin production (p < 0.05). Therefore, PePpoC proteins affect more growth and development, patulin biosynthesis and pathogenicity of P. expansum by regulating C8 MVOC-mediated G protein signaling transduction.
Keywords: C8 moldy VOCs; G protein signal transduction; Penicillium expansum; pathogenicity; patulin biosynthesis; psi-producing oxygenase.