Advances in the biosynthesis, gene mining, and molecular mechanisms of cucurbitacin in Cucurbitaceae crops

Cucurbitacin, a highly oxidized tetracyclic triterpenoid compound, is a common secondary metabolite in Cucurbitaceae crops. Its presence imparts a bitterness to the fruit, significantly reducing its quality. However, the accumulation of cucurbitacin enhances the plants resistance to pests and diseases, earning it the reputation of a 'green pesticide'. In recent years, cucurbitacin has attracted extensive attention from researchers. Therefore, this review summarizes the identification, gene mapping, and marker development, biosynthesis and regulation, transport mechanisms, and the domestication of non-bitter Cucurbitaceae varieties. Additionally, it provides insights into the breeding of Cucurbitaceae crops and the in vitro biosynthesis of cucurbitacin.