THE OCS ELEMENT IN THE SOYBEAN GH2 4 PROMOTER IS ACTIVATED BY BOTH ACTIVE AND INACTIVE AUXIN AND SALICYLIC-ACID ANALOGS/

The octopine synthase (ocs or ocs-like) element has been previously re ported to be responsive to the plant hormones, auxin, salicylic acid, and methyl jasmonate. Using transient assays with carrot protoplasts, we have demonstrated that an ocs element from the soybean auxin-induci ble GH2/4 promoter is not only activated by strong auxins (i.e., 2,4-d ichlorophenoxyacetic acid, 2,4, 5-trichlorophenoxyacetic acid, alpha-n aphthalene acetic acid) and salicylic acid, but also by weak auxin ana logues (beta-naphthalene acetic acid), inactive auxin analogs (i.e., 2 ,3-dichlorophenoxyacetic acid, 2,4,6-trichlorophenoxyacetic acid), and inactive salicylic acid analogs (3-hydroxybenzoic acid and 4-hydroxyb enzoic acid). Our results indicate that the ocs element in the GH2/4 p romoter is not selectively induced by plant hormones and might functio n similarly to tandem AP-1 sites in some animal glutathione S-transfer ase (GST) genes. The ocs element, like the AP-1 sites in animal GST pr omoters, may be induced not only by certain hormones but also by some non-hormonal stress-inducing or electrophilic agents.