The myrosinase gene family in Arabidopsis thaliana: gene organization, expression and evolution

Abstract

Myrosinase (thioglucoside glucohydrolase, EC 3.2.3.1.) is in Brassicaceae species such as Brassica napus and Sinapis alba encoded by two differentially expressed gene families, MA and MB, consisting of about 4 and 10 genes, respectively. Southern blot analysis showed that Arabidopsis thaliana contains three myrosinase genes. These genes were isolated from a genomic library and two of them, TGG1 and TGG2, were sequenced. They were found to be located in an inverted mode with their 3' ends 4.4 kb apart. Their organization was highly conserved with 12 exons and 11 short introns. Comparison of nucleotide sequences of TGG1 and TGG2 exons revealed an overall 75% similarity. In contrast, the overall nucleotide sequence similarity in introns was only 42%. In intron 1 the unusual 5' splice border GC was used. Phylogenetic analyses using both distance matrix and parsimony programs suggested that the Arabidopsis genes could not be grouped with either MA or MB genes. Consequently, these two gene families arose only after Arabidopsis had diverged from the other Brassicaceae species. In situ hybridization experiments showed that TGG1 and TGG2 expressing cells are present in leaf, sepal, petal, and gynoecium. In developing seeds, a few cells reacting with the TGG1 probe, but not with the TGG2 probe, were found indicating a partly different expression of these genes.

Dolichol Biosynthesis and Its Effects on the Unfolded Protein Response and Abiotic Stress Resistance in Arabidopsis

“…Tryptic peptides were resolved by matrix-assisted laser-desorption ionization time of flight (MALDI-TOF) MS (Autoflex II TOF/TOF; Bruker) and analyzed by Mascot at www.Matrixscience.com. The smaller band corresponded to the glycoprotein b-thioglucoside glucohydrolase encoded by TGG1 in Arabidopsis (Xue et al, 1995;Husebye et al, 2002). TGG1 is localized in the vacuole, and underglycosylated TGG1 was also found in the stt3a mutant of Arabidopsis in a previous study (Koiwa et al, 2003).…”

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

“…Also interesting among the set more highly expressed in the Ler ecotype are several loci in aliphatic glucosinolate synthesis, including CYP79F1, which exists upstream of CYP83A1 (Hansen et al, 2001;Reintanz et al, 2001;Chen et al, 2003), CYP83A1 itself, and 2-oxoglutarate-dependent dioxygenase (AOP3), which exists downstream of CYP83A1 (Kliebenstein et al, 2001b); Trp synthetase (TSB2; Last et al, 1991) also potentially impacts aliphatic glucosinolate synthesis because it is postulated to feed substrates into the aliphatic glucosinolate pathway via CYP79B2 and CYP79B3 . Contrasting with these glucosinolate synthetic enzymes that are more highly expressed in the Ler ecotype, one locus more highly expressed in the Col ecotype codes for thioglycosyl hydrolase (TGG2, myrosinase), which degrades glucosinolates to release toxic derivatives (Xue et al, 1995).…”

Jasmonate is essential for insect defense in Arabidopsis

“…Because so little is known about insect defense in Arabidopsis, these results leave open the possibility that redundant pathways bypass jasmonate signaling or that other mechanisms exist in Arabidopsis that lead to significant protection against insects even in the absence of jasmonatemediated processes. For example, in common with other members of the Brassicaceae, Arabidopsis contains the constitutive glucosinolate-myrosinase system that is postulated to act as a defense against chewing insects (23,24).…”