Proteomic analysis of the inhibitory effect of chitosan on Penicillium expansum

The antimicrobial effect of chitosan on Penicillium expansum, a major postharvest pathogen of pome fruit, and the possible mechanisms involved in its effect were examined in this study. Chitosan strongly inhibited spore germination and hyphal growth of P. expansum. Light microscopy and transmission electron microscopy observations revealed that chitosan also caused morphological changes in hyphae and conidia, such as abnormal branching and vacuolation. Proteomic changes in P. expansum after chitosan treatment were analyzed by two-dimensional electrophoresis (2-DE) and mass spectrometry (MS) analysis, and 26 proteins were ambiguously identified and categorized based on their putative biological function. Proteins related to DNA or protein biosynthesis, carbohydrate metabolism and energy production were decreased in relative protein abundance, while proteins involved in antibiotics resistance and defense response increased in relative protein abundance. Changes in abundance of these identified proteins were in accordance to the observed physiological and morphological changes of the fungi cells. Altogether, these experimental results provide a detailed illustration of the responses to chitosan in P. expansum, and widen our knowledge on the potential antifungal mechanisms of chitosan.