Glucosinolate Synthesis in the Context of Plant Metabolism

The glucosinolate biosynthesis pathway is an important component of plant secondary metabolism. The transcriptional regulation of this pathway is well described, including the nature of corresponding transcription factors. However, glucosinolate synthesis requires also cofactors and intermediates derived from primary metabolism. In particular the pathway has to be well coordinated with sulphur metabolism, through the donor of activated sulphate, 3'-phosphoadenosine-5'-phosphosulphate (PAPS). The availability of PAPS and other intermediates thus affects the rate of glucosinolate synthesis. Interestingly, very recently three enzymes connected to glucosinolate synthesis have been shown to undergo redox regulation, pointing to the complexity of the control of the pathway. In addition, glucosinolate metabolism is divided across multiple cellular compartments including plastids, cytosol, vacuole, endomembrane structures, as well as mitochondria. Therefore, a suite of transporters are necessary to ensure the exchange of intermediates between the compartments but also to enable the long-distance transport between plant organs and tissues. Here we review our current knowledge on how glucosinolate synthesis is connected to general plant metabolism, on the newly discovered redox regulation of the pathway and on the role of various transporters in glucosinolate biosynthesis and their inter-and intracellular distribution. We believe that these processes hold a key for successful engineering of glucosinolate pathways and improved yield and nutritional properties of crops