Glucosinolates

Abstract

Plants resist herbivorous insects and pathogens by employing specialised metabolites as chemical defences. In the case of constitutively present activated defences, an inactive precursor is stored and activated upon damage or attack by biotic stressors releasing high amounts of toxic and bioactive products. Glucosinolates are a group of defence compounds found in cruciferous vegetables. They consist of a nitrogen‐ and sulfur‐containing core structure and an amino acid‐derived, variable side chain. Enzymatic activation of glucosinolates further amplifies their chemical diversity, as one glucosinolate can generate different bioactive metabolites. These serve diverse functions in plant–insect and plant–pathogen interactions. Insects, however, have evolved many creative adaptations to avoid toxic glucosinolate‐derived metabolites. For humans, glucosinolates and their activation products have many beneficial health effects and promising applications in sustainable agriculture. Key Concepts Plants of the Brassicales order store nontoxic glucosinolates as precursors of bioactive compounds to defend themselves against herbivores and pathogens. Glucosinolate composition varies across and within plant species as well as between tissues, developmental stages and environmental conditions. Upon attack, enzymatic activation of glucosinolates initiated by myrosinase enzymes further amplifies their structural diversity, which is pivotal for the plants' resistance against a wide range of biotic enemies. Against harmful bacteria and fungi, activation of particularly indolic glucosinolates in intact plant tissue can also occur through atypical myrosinases. Glucosinolate‐derived bioactive compounds function in both direct and indirect defence against insect herbivores. Many herbivores have adapted towards feeding on glucosinolate‐containing plants and have developed creative counteradaptations against the glucosinolate–myrosinase system, while nonadapted herbivores rely on detoxification of glucosinolate‐derived active compounds. Apart from their defensive functions, glucosinolates serve as molecular signal to feedback regulate plant metabolism, growth and defence. The chemical diversity of glucosinolates and their hydrolysis products provides benefits for human health and promising applications for sustainable agriculture.

Same Difference? Low and High Glucosinolate Brassica rapa Varieties Show Similar Responses Upon Feeding by Two Specialist Root Herbivores

“…Humans and livestock as well as insects and microbes exploit these plants as food source. To defend themselves against herbivores, plants in the Brassicaceae produce glucosinolates (GSLs), a group of plant secondary metabolites (Jeschke and Burow, 2018). These compounds are located in all parts of the plants including in the roots.…”

Sugar transporters enable a leaf beetle to accumulate plant defense compounds

“…Glucosinolates are hydrophilic defense compounds produced by plants of the order Brassicales that, together with the plant β-thioglucosidase enzyme myrosinase, constitute an activated two component defense system [12][13][14] . When tissue damage brings both components together, glucosinolates are rapidly hydrolyzed to unstable aglucones that give rise to different products 15 of which isothiocyanates are the most detrimental to small herbivores [16][17][18][19] .…”

New Insights on the Role of Allyl Isothiocyanate in Controlling the Root Knot Nematode Meloidogyne hapla

“…This so-called biofumigation makes use of a natural plant defense mechanism of the Brassicaceae family producing the secondary metabolites glucosinolates (GSLs). More than 200 different GSLs are known, which are derived from glucose and amino acids containing sulfur and nitrogen [6,7]. After the damage of the plant tissue, GSLs stored in the vacuoles are hydrolyzed through the enzyme myrosinase (Thioglucosidase: EC 3.2.1.147), stored in myrosin grains (myrosin cells), and then converted into toxic isothiocyanates (ITCs) [7,8].…”

“…More than 200 different GSLs are known, which are derived from glucose and amino acids containing sulfur and nitrogen [6,7]. After the damage of the plant tissue, GSLs stored in the vacuoles are hydrolyzed through the enzyme myrosinase (Thioglucosidase: EC 3.2.1.147), stored in myrosin grains (myrosin cells), and then converted into toxic isothiocyanates (ITCs) [7,8]. If, as a result of an attack by pests or pathogens, plant cells are destroyed, ITCs are released and repel or kill the invading organism.…”