Suppression of ergosterol biosynthesis by dictamnine confers resistance to gray mold on harvested fruit

Botrytis cinerea is a major cause of postharvest rot in fresh fruits and vegetables worldwide. Consequently, the pursuit of environmentally friendly and efficient alternatives to fungicides has emerged as a hot spot of research. In this study, it was found that dictamnine (DIC, 4-methoxyfuro [2,3-β] quinoline), an active ingredient from Dictamnus dasycarpus Turcz, efficiently inhibited spore germination and mycelial growth of B. cinerea, alleviated the development of lesions caused by B. cinerea on postharvest apples, kiwifruits, cherry tomatoes and strawberries in a dose-dependent manner. RNA sequencing analysis followed by Gene Ontology (GO) term enrichment revealed that functional genes related to cell membrane function were significantly enriched, while most genes associated with ergosterol biosynthesis were down-regulated. Molecular docking indicated that DIC bound to the rate-limiting enzymes BcERG1 (squalene monooxygenase) and BcERG11 (Lanosterol 14-alpha demethylase) at -7.1 and -7.2 kcal mol^-1, respectively. Additionally, it was observed that the application of DIC led to a decrease in ergosterol content, which compromised membrane integrity and normal membrane potential. Interestingly, exogenous ergosterol addition partially restored the inhibitory effect of DIC on the germination of B. cinerea spores and the lesion development on apple fruit. Taken together, these results indicate the potential for utilizing DIC as a promising antifungal substitute for controlling gray mold in postharvest fruit.