Glucosinolates and their potential role in plant

Glucosinolates are sulfur- and nitrogen-containing plant secondary metabolites common in the Brassicaceae and related plant families. In the plant, they coexist with an endogenous ?-thioglucosidase (EC 3.2.3.1) called myrosinase, though glucosinolates are stored in the vacuoles of so-called S-cells and myrosinase in separate but adjacent cells. Upon plant tissue disruption, glucosinolates are released at the damage site and become hydrolyzed by myrosinase. The chemical nature of the hydrolysis products depends on the structure of the glucosinolate side chain, plant species and reaction conditions. Biosynthesis of glucosinolates comprises three phases: (i) amino acid chain elongation, in which additional methylene groups are inserted into the side chain, (ii) conversion of the amino acid moiety to the glucosinolate core structure, (iii) and subsequent side chain modifications. Glucosinolate pattern differs between species and ecotype as well as between and even within individual plants, depending on developmental stage, tissue and photoperiod. A number of environmental conditions such as light plant, nutritional status, fungal infection, wounding and insect damage can alter the glucosinolate pattern significantly. The change of the glucosinolate profile by several environmental factors has brought forward different theories regarding their potential roles in the plant. However, the most accepted theory is that the glucosinolate-myrosinase system is involved in defense against herbivores and pathogens. This review summarized recent progress in glucosinolate biosynthesis, degradation and organization of the myrosinase-glucosinolate system. Furthermore, current knowledge of the potential role of glucosinolates in the plant, especially in plant defense, is discussed.