Tissue-specific expression and localization of safener-induced glutathione S -transferase proteins in Triticum tauschii

Abstract

Glutathione S-transferase (GST; EC 2.5.1.18) gene expression was examined in the coleoptile and new leaf tissue of etiolated shoots of the diploid wheat species Triticum tauschii (Coss.) Schmal., which is considered to be a progenitor and the D-genome donor to cultivated, hexaploid bread wheat Triticum aestivum L. GST expression (mRNA, protein, and enzyme activity with a herbicide substrate) in these shoot tissues was examined in response to herbicide safener treatment. Two different antibody probes, raised against the same safener-inducible GST protein (TtGSTU1) but differing in their specificity, were utilized to determine tissue distribution and subcellular localization of GST proteins in etiolated shoots. GST transcripts, immunoreactive GST proteins, and herbicide-metabolizing activity were all highest in the coleoptile of etiolated, safener-treated T. tauschii shoots. Anti-GST immunolabeling was strongest in the outer epidermal and adjoining sub-epidermal cells in both coleoptiles and new leaves following safener treatment. Our data indicate that safeners protect grass crops from herbicide injury by dramatically inducing the expression of GST proteins in the outer cell layers of the coleoptile, which prevents the herbicide from reaching the sensitive new leaves of etiolated shoots as they emerge from the soil.

Safeners recruit multiple signalling pathways for the orchestrated induction of the cellular xenobiotic detoxification machinery in Arabidopsis

“…The failure of safeners to induce herbicide tolerance in Arabidopsis and other dicots may thus be caused by the properties of the enzymes that are induced after safener treatment rather than a general lack of safener responsiveness. Detoxification enzymes in dicots may lack the specificity required for herbicide metabolization, or else, tissue specificity and level of expression may be inappropriate to provide protection (Riechers et al 2003;DeRidder & Goldsbrough 2006).…”

“…Class II TGA transcription factors are thus involved in the activation of multiple stress responses. They mediate the induction of PR gene expression and SAR in response to biotrophic pathogens (Zhang et al 2003), and they are involved in the activation of detoxification responses after exposure to chemical stresses (Fode et al 2008;Mueller et al 2008). Furthermore, class II TGA factors were recently shown to modulate the ethylene and jasmonic acid-dependent responses to necrotrophic pathogens (Zander et al 2009).…”

“…The regulated expression of these genes is mediated by TGA factors, a specific class of conserved bZip transcription factors (Jakoby et al 2002). The induced expression of the PR1 gene, for example, requires TGA2, TGA5 or TGA6, which are functionally redundant members of the TGA factor family in Arabidopsis (Zhang et al 2003). To investigate a possible role of these TGA factors and to further substantiate the relevance of as-1-like elements in the regulation of the In2.1 promoter, we analysed the expression of the 0.8 kb promoter:reporter gene construct in a TGA factor-deficient Arabidopsis mutant.…”

“…To investigate a possible role of these TGA factors and to further substantiate the relevance of as-1-like elements in the regulation of the In2.1 promoter, we analysed the expression of the 0.8 kb promoter:reporter gene construct in a TGA factor-deficient Arabidopsis mutant. A quadruple mutant (tga2/3/5/6) was chosen for this experiment, which shows reduced background expression of the PR1 gene as compared with the tga2/5/6 triple mutant (Zhang et al 2003;Kesarwani et al 2007). The fold induction of GUS activity in safener-treated plants as compared with mock-treated controls was 33 times higher in the wild type than in the tga2/3/5/6 mutant background (Fig.…”

Differential Induction of Glutathione Transferases and Glucosyltransferases in Wheat, Maize and Arabidopsis thaliana by Herbicide Safeners

“…In a recent elegant proteomics study, a comprehensive set of GSTFs, GSTLs and GSTUs were all shown to be upregulated in the coleoptiles of seedlings of Triticum tauschii treated with the safener fluxofenim (Zhang and Riechers, 2004). Of the safener-inducible GSTs, the GSTUs and GSTFs have been the most studied due to their roles in herbicide detoxification, reviewed by Edwards and Dixon (2000).…”