COORDINATED ACTIVATION OF AS-1-TYPE ELEMENTS AND A TOBACCO GLUTATHIONE-S-TRANSFERASE GENE BY AUXINS, SALICYLIC-ACID, METHYL-JASMONATE AND HYDROGEN-PEROXIDE

The molecular mechanism of signal transduction pathways which mediate the action of phytohormones are poorly understood. Recently, we and ot hers have shown that the as-1 type cis-acting elements can respond to auxin and salicylic acid, two well-characterized signaling molecules i n plants. In the present work, we have examined a comprehensive set of physiological and abiotic agents and found that auxin, salicylic acid and methyl-jasmonate are three effective inducers of the as-1-type el ements in transgenic tobacco. Using a cell suspension culture containi ng a synthetic promoter-GUS fusion, we demonstrated rapid and sensitiv e induction of the as-1-type element by these phytohormones. Furthermo re, a tobacco glutathione S-transferase gene, GNT35, that contains an as-1-type binding site in its promoter is also inducible by auxin, sal icylic acid and methyl-jasmonate with similar kinetics. As Ulmasov ef al. have recently reported, we found that the as-1-type elements can a lso respond to weak/inactive analogues of auxin and salicylic acid. In addition, we show that hydrogen peroxide can also effectively activat e the expression of GNT35 as well as the as-1-type element in a cell s uspension culture, but not with whole seedlings. These results are dis cussed with respect to the possible mechanism(s) through which a singl e cis element may respond to a diverse array of molecules.