Identification and expression pattern of a <scp>g</scp>lutathione <scp>S</scp>‐transferase in <i><scp>E</scp>chinochloa crus‐galli</i>

Abstract

Summary Plant glutathione S‐transferase ( GST ) forms a major part of the herbicide detoxification enzyme network in plants. A GST cDNA was isolated from E chinochloa crus‐galli and characterised. The gene, designated E c GST 1 ( E . crus‐galli GeneBank no: JX518596 ), has a 684 bp open reading frame predicted to encode a 25 kD protein. Sequence alignment showed that E c GST 1 is a GST homologue. Its expression in response to quinclorac treatment was monitored in seedlings (leaves and roots) and adult plants (leaves, roots, stems and seeds) of quinclorac‐resistant ( R ) and susceptible ( S ) biotypes of E . crus‐galli . E c GST 1 expression was 1.5–3 times greater in the R plants than in the S plants. However, after exposure to quinclorac, the difference in the expression levels of E c GST 1 in R plants, compared with S plants, increased to a ratio of 6–10. Enhanced E c GST 1 levels should enable greater quinclorac detoxification following quinclorac stimulation in R plants. GST ‐based metabolism may be partially responsible for resistance to quinclorac in E . crus‐galli . The results suggest a new resistance mechanism for this R biotype in Chinese rice fields.