METHOXYLATION MODIFIES THE ACTIVITY OF 1,2-BENZISOXAZOLE-3-ACETIC ACID - 6,7-DIMETHOXY-1,2-BENZISOXAZOLE-3-ACETIC ACID IS AN AUXIN ANTAGONIST IN CYTOKININ MEDIATED PROCESSES

The insertion of a methoxy group in different positions of the aromati c ring modifies the activity of 1,2-benzisoxazole-3-acetic acid (BOAA) , a specific morphogenetic compound with no activity on cell elongatio n or root growth. Monomethoxylation in the 4- and 7-position is critic al in determining the kind of activity: 4-OMeBOAA induces stem elongat ion, inhibits root growth and does not improve shoot production; 7-OMe BOAA inhibits stem elongation and shoot production and is unable to in duce root growth. 6,7-OMeBOAA, inactive on stem elongation and root gr owth, is unable to induce the expression of Pg5-GUS gene in the presen ce of BAP and inhibits the expression of this gene when induced by BAP plus IAA. Furthermore, 6,7-OMeBOAA inhibits completely shoot producti on and can therefore be regarded as an auxin antagonist in these cytok inin-mediated processes.