Myrosinase: gene family evolution and herbivore defense in Brassicaceae

Abstract

Glucosinolates are a category of secondary products present primarily in species of the order Capparales. When tissue is damaged, for example by herbivory, glucosinolates are degraded in a reaction catalyzed by thioglucosidases, denoted myrosinases, also present in these species. Thereby, toxic compounds such as nitriles, isothiocyanates, epithionitriles and thiocyanates are released. The glucosinolate-myrosinase system is generally believed to be part of the plant's defense against insects, and possibly also against pathogens. In this review, the evolution of the system and its impact on the interaction between plants and insects are discussed. Further, data suggesting additional functions in the defense against pathogens and in sulfur metabolism are reviewed.

Variations in CYP74B2 (Hydroperoxide Lyase) Gene Expression Differentially Affect Hexenal Signaling in the Columbia and Landsberg erecta Ecotypes of Arabidopsis

“…The differential expression of CYP83A1 in these ecotypes partially explains the different basal glucosinolate profiles in the Col and Ler ecotypes (Kliebenstein et al, 2001a) and the higher overall glucosinolate content of the Ler ecotype (Jander et al, 2001). Presumably these different basal levels of glucosinolates contribute to variations in ecotype resistance to insect predators as myrosinases release toxic glucosinolate derivatives (Rask et al, 2000). But, in the long run, it is the induced levels of glucosinolates that provide the most effective, sustained protection against insect damage.…”

Are isothiocyanates potential anti-cancer drugs?

“…In Brassica vegetables, there are typically 0.5-28 µmol aliphatic/ aromatic glucosinolates per gram dry weight and 0.7-8 µmol indolyl glucosinolates per gram dry weight. Glucosinolates are normally localized to the cytoplasm of plant tissue [9] . Myrosinase is expressed on the external surface of the plant cell wall, so it cannot access the glucosinolates [9] .…”

Categories of Resistance to Greenbug (Homoptera: Aphididae) Biotype I in <B> <I>Aegilops tauschii</I> </B> Germplasm

“…Plants in the Brassicaceae family, which includes Arabidopsis thaliana, accumulate glucosinolates, a family of secondary metabolites that are sources of thioacyanates and other breakdown products that are toxic to some aphids (Rask et al, 2000;Halkier and Gershenzon, 2006). Levy et al, (2005) showed that the expression level of the IQD1 (At3g09710) gene, which encodes a transcription factor that is responsible for glucosinolate accumulation, impacts host plant choice by GPA.…”

“…However, when acted upon by myrosinases, glucosinolates produce toxic thiocyanates and other breakdown products that act as defensive compounds against insects (Chew, 1988;Louda and Mole 1991;Rask et al, 2000). In Arabidopsis, β-thioglucoside glucohydrolases encoded by TGG1 and TGG2 (At5g25980 and At5g26000) contribute to the majority of the myrosinase activity (Barth and Jander, 2006).…”