Herbicide Safener-Inducible Gene Expression in Arabidopsis thaliana

The potential use of a new chemical-inducibie gene expressionsystem in Arabidopsis thaliana has been examined. The systemis based on the maize In2-2 promoter which is activated by benzenesulfonamideherbicide safe-ners. Plants transformed with the ß-glucuronidase(gus) reporter gene under the control of the In2-2 promoterwere grown in the presence of different safeners and the inducedGUS activity pattern was studied histochemically. In the absenceof safeners, the In2-2 promoter was not active. Applicationof different safeners induced distinct gus expression patterns,including expression in the root, hy-dathodes, and the shootapical meristem. Plants maintained continuously on inducingconcentrations of the safeners were retarded in growth. Thegrowth inhibition effects of the Sa5 safener could be overcomein a sul-fonylurea-resistant background. In2-2 promoter activitycould also be induced by the sulfonylurea herbicide chlor-sulfuron.In the sulfonylurea-resistant background, which derives fromherbicide-resistant acetolactate synthase activity, inductionof the In2-2 promoter by chlorsulfuron was lower. Furthermore,branched-chain amino acids, known to inhibit acetolactate synthaseactivity, also induced In2-2 promoter activity. Our data suggesta strong correlation between In2-2 expression and inhibitionof the acetolactate synthase activity. (Received November 12, 1996; Accepted February 21, 1997)