Efficacy of pterostilbene inhibition of postharvest anthracnose on papaya fruit and antifungal mechanisms against Colletotrichum gloeosporioides

Colletotrichum gloeosporioides is the main pathogen causing anthracnose disease on a wide range of fruit and vegetables, leading to substantial economic losses. In present study, a plant natural product pterostilbene (PTE) was found effective in alleviation of postharvest anthracnose on papaya fruit. In addition, PTE inhibited the mycelium growth, conidium germination and appressorium formation of C. gloeosporioides. To investigate the underlying molecular mechanisms of antifungal activity of PTE, a transcriptomic analysis was performed. The transcriptomics identified 4131 and 3611 differentially expressed genes (DEGs) effected by PTE treatment at 4 h and 20 h, respectively. The gene function (GO) and metabolic pathway (KEGG) analysis of DEGs showed that PTE significantly affected the pathways related to carbohydrate and lipid metabolism, which play essential roles in maintaining the integrity and normal function of cell wall, plasma membrane and mitochondria of fungal cells. The biochemical assays as well as fluorescent and electron microscope observation demonstrated that the PTE treatment deformed the morphology and ultrastructure of mycelia and conidia, compromised the integrity of cell wall and plasma membrane, and impaired the function of cell wall, plasma membrane and mitochondria. Altogether, our findings improved the understanding of the antifungal activity of PTE and the underlying mechanisms of action at molecular level, thus supporting PTE as a potential agent in alleviating postharvest anthracnose by C. gloeosporioides.