Update on glucosinolate metabolism and transport

Glucosinolates are secondary plant metabolites found mainly in the order Capparales. Tissue disruption allows rapid enzymatic degradation of glucosinolates by specific thioglucosidases, denoted myrosinases. Within the last few years, significant progresses in our understanding of glucosinolate biosynthesis and degradation have been achieved. In particular, the Arabidopsis thaliana genome-sequencing project has accelerated the identification and characterization of genes involved in the glucosinolate metabolism. More evidence has accumulated for the hypothesis that the glucosinolate-myrosinase system has evolved from the prevalent system of cyanogenic glucosides and corresponding O-β-glucosidases. Glucosinolates have been shown to be taken up by a specific carrier system and transported by phloem. The de novo biosynthesis, degradation and transport of glucosinolates may constitute a delicately regulated dynamic diagram, through which various physiological functions are fulfilled. There is a rising interest in controlling the level of glucosinolates in crops to improve pest resistance and nutritional value. Genes identified in Arabidopsis thaliana will provide important tools to initiate molecular strategies to modulate the quantity and quality of glucosinolates in a tissue-specific manner in closely related Brassica crops. This review summarizes current knowledge on glucosinolate biosynthesis, degradation and mobilization, and provides a comprehensive discussion and update on the regulation, physiological functions and genetic engineering of glucosinolate metabolism and transport.