Over-expression of a specific soybean GmGSTU4 isoenzyme improves chloroacetanilide herbicide tolerance of transgenic tobacco plants

Abstract

Plant glutathione transferases (GSTs) have a major role in herbicide detoxification. Soybean (Glycine max L.) GmGSTs have been well studied for their correlation in herbicides selectivity towards diphenyl ether, chloroacetanilide and sulfonylurea herbicides. Chloroacetanilide herbicide tolerance was assayed in vitro by measuring the growth inhibition of wild type (wt) and transgenic tobacco seedlings from cultivars (Basmas, Virginia, Burley) in the presence of 7.5 and 15 mg/L of alachlor and metolachlor. Alachlor caused strong inhibition of shoot and root growth of wt tobacco plants. All the transgenic Basmas lines showed significantly higher shoot and root elongation at 7.5 mg/L alachlor, with line BAGST-3 exhibiting the greatest tolerance. However, at 15 mg/L alachlor, growth was highly reduced in transgenic and wt plants. In Burley, only line BUGST-2 has statistically significant greater mean of root and shoot length compared to wt under the two doses. On the contrary, Virginia has reduced growth which was similar to the wt. Metolachlor toxicity was less severe compared to alachlor. Growth of the transgenic lines of the three cultivars was not significantly greater in either metolachlor concentrations tested, compared to wt plants, except line BAGST-3 which exhibited significantly greater mean of shoot and root elongation at 7.5 mg/L. Transgene expression was determined quantitatively using Real Time qPCR, lines BAGST-3 and BUGST-2 showed greater expression of Gmgstu4 in shoot compared to root. These results confirm that overexpression of GmGSTU4 in tobacco provides higher catalytic activities towards xenobiotics, resulting for future use in environmental cleanup of alachlor.