Integration of wounding and osmotic stress signals determines the expression of the AtMYB102 transcription factor gene.

Transcript levels of the Arabidopsis R2R3-AtMYB102 transcription factor gene, previously named AtM4, are rapidly induced by osmotic stress or abscisic acid (ABA) treatment. Reporter gene expression studies revealed that in addition, wounding is required for full induction of the gene. Histochemical analysis showed a local beta-glucuronidase induction around the wounding site, especially in veins. In ABA-treated plants, wounding-induced beta-glucuronidase activity could be mimicked by the wound signaling compound methyl jasmonate. In silico studies of the AtMYB102 promoter sequence and its close homolog AtMYB74 demonstrated several conserved putative stress regulatory elements such as an ABA-responsive element, its coupling element 1 (CE1), and a W box. Interestingly, further studies showed that the 5'-untranslated region is essential for the osmotic stress and wounding induced expression of the AtMYB102 gene. This 5'-untranslated region contains putative conserved regulatory elements such as a second W box and an overlapping MYB-binding element. These studies suggest that AtMYB102 expression depends on and integrates signals derived from both wounding and osmotic stress.