Chalcone Synthase in Flavonoid Biosynthesis: Structural Features, Regulatory Mechanisms, and Functions in Plant Defense

Chalcone synthase (CHS, EC 2.3.1.74) is a key entrance enzyme in the biosynthesis of flavonoids from the common phenylpropanoid precursor into a specific flavonoid branch. Beyond its catalytic role, CHS functions as a metabolic hub linking flavonoid production, hormone signaling, and biotic stress defense, and contributes to pigmentation, ultraviolet protection, plant growth, development, and environmental adaptation. Recent structural studies further suggest that chalcone isomerase-like proteins can modulate CHS catalytic efficiency and product specificity, although the physiological significance of this interaction remains incompletely understood across plant species. This review summarizes recent advances in CHS structure and function, with emphasis on metabolic regulation, gene family evolution, disease resistance, and metabolic engineering. Future research should prioritize metabolic flux quantification, functional validation of CHS family members, causal analysis of disease resistance, and precision breeding applications.