EXPRESSION OF AN AUXIN-INDUCIBLE PROMOTER OF TOBACCO IN ARABIDOPSIS-THALIANA

The expression of the auxin-inducible Nt103-1 gene of tobacco was stud ied in Arabidopsis thaliana. For this purpose we introduced a gene fus ion between the promoter of the gene and the beta-glucuronidase report er gene (GUS) into Arabidopsis thaliana. The expression and location o f GUS activity were studied histochemically in time and after incubati on of seedlings on medium containing auxins or other compounds. The au xins 2,4-dichlorophenoxyacetic acid (2,4-D), indole-3-acetic acid (IAA ), and 1-naphthylacetic acid (1-NAA) were able to induce GUS activity in the root tips of transgenic seedlings. The auxin transport inhibito r 2,3,5-triiodobenzoic acid was able to induce GUS activity not only i n the root tip, but also in other parts of the root. Induction by the inactive auxin analog 3,5-dichlorophenoxyacetic acid was much weaker. Compounds like glutathione and the heavy metal CuSO4 were weak inducer s. GUS activity observed after induction by glutathione was located in the transition zone. Salicylic acid and compounds increasing the conc entration of hydrogen peroxide in the cell were also very well able to induce GUS activity in the roots. The possible involvement of hydroge n peroxide as a second messenger in the pathway leading to the inducti on of the Nt103-1 promoter is discussed.