The myrosinase (thioglucoside glucohydrolase) gene family in Brassicaceae

Abstract

The glucosinolate hydrolyzing enzymes myrosinase (thioglucoside glucohydrolase, EC 3.2.3.1) are encoded by a multigene family consisting of two subgroups. The first two nuclear genes representing each of these two subgroups of the new gene family, Myr1.Bn1 and Myr2.Bn1, from Brassica napus have been cloned and sequenced. Based on conserved regions in cDNA of three species, PCR (polymerase chain reaction) primers were made, and used to amplify and characterize the structure of the myrosinase genes in seven species of Brassicaceae. Southern hybridization analysis of PCR products and genomic DNA indicates that myrosinase is encoded by at least 14 genes in B. napus, with similar numbers in the other species of Brassicaceae investigated. The Myr1 gene cloned from B. napus has a 19 amino acid signal peptide and consists of 11 exons of sizes ranging from 54 to 256 bp and 10 introns of sizes from 75 to 229 bp. The Myr2 gene has a 20 amino acid signal peptide and consists of 12 exons ranging in size from 35 to 262 bp and 11 introns of sizes from 81 to 131 bp. The exons from the two genes have 83% homology at the amino acid level. The intron-exon splice sites are of GT..AG consensus type. The signal peptides and presence of sites for N-linked glycosylation, suggest transport and glycosylation through the ER-Golgi complex. The differences between the two genes are discussed on the basis of their predicted expression at different developmental stages in the plant. Both genes show homology to a conserved motif representing the glycosyl hydrolase family of enzymes.

Defence mechanisms of Brassicaceae: implications for plant-insect interactions and potential for integrated pest management. A review

“…Brassica plants contain the enzyme myrosinase (β-thioglucoside glucohydrolase, thioglucosidase, EC 3.2.3.147 (formerly EC 3.2.3.1) (Bones and Slupphaug, 1989;Bones, 1990;Bones andRossiter, 1996, 2006), which is thought to be exclusively present in myrosin cells (Thangstad et al, 1990Bones et al, 1991;Höglund et al, 1991;Husebye et al, 2002;Thangstad et al, 2004;Kissen et al, 2009). In brassicas, myrosinases can be divided into three different gene families; the MA, MB and MC families (Xue et al, 1992;Chadchawan et al, 1993;Lenman et al, 1993;Thangstad et al, 1993;Falk et al, 1995). Furthermore, myrosinases are glycosylated dimeric proteins with subunit molecular weights from 62 to 75 kDa (Bones and Slupphaug, 1989;Bones and Rossiter, 1996).…”

Response of aliphatic glucosinolate biosynthesis to signaling molecules in MAM gene knockout mutants of Arabidopsis

“…In Wild-type, the changing patterns of total and short-chain AGSL contents over time after hormone treatment were consistent with those of MAM1 and MAM3 expression levels; after MeJA treatment the AGSL contents increased until 24 h and then declined (Figure 2A), after ACC treatment the AGSL contents raised continually ( Figure 3A), and after SA treatment the AGSL contents decreased at 4 h and then recovered ( Figure 4A). It was reported that genes encoding myrosinase were pathogen-and SA-inducible (Textor and Gershenzon 2009;Thangstad et al 1993). At 48 h after SA treatment, expression levels of MAM1 and MAM3 were much higher than those at 0 h (Figure 1).…”

Expression of a Zeatin-O-Glucoside-Degrading [beta]-Glucosidase in Brassica napus

“…The highest identity (44%) was found with a /3-glucosidase from maize (Brzobohaty et al, 1993). The identity to the three types of myrosinases in B. napus was 35 to 40% (Falk et al, 1992(Falk et al, , 1995aThangstad et al, 1993).…”