Dissecting inhibitory effect of boric acid on virulence and patulin production of Penicillium expansum

Pencillium expansum, the causal agent of blue mould rot, is one of the most destructive postharvest pathogens of pome fruit. It is also considered as the main source of the mycotoxin patulin which can lead to serious health problems. In the present study, the effects of exogenous boric acid (BA) on virulence and patulin production of P. expansum were evaluated. The results showed that 0.3% BA significantly inhibited the development of P. expansum in vitro and resulted in lower virulence to apple fruit. Moreover, BA suppressed the metabolism of carbohydrate, lipid and protein, reduce patulin production in P. expansum. Further analysis revealed that the expressions of the majority of the 15 genes involved in patulin biosynthesis were down-regulated under BA treatment. In addition, a global view of proteome alteration of P. expansum spores in response to 0.3% BA was acquired by an iTRAQ-based (Isobaric tags for relative and absolute quantitation) quantitative proteomic analysis. A total of 315 differentially expressed proteins (DEPs) (87 up-regulated and 228 down-regulated) were identified, and these DEPs were mainly involved in carbohydrate and protein metabolic pathways. Among them, septins and proteins related to ribosome component or ribosome biosynthesis were noticed for their significant up-regulation. Our results provided novel information for understanding the mechanism, by which BA regulated the growth of P. expansum and its virulence.