PROMOTER REGIONS OF THE EXTA EXTENSIN GENE FROM BRASSICA-NAPUS CONTROL ACTIVATION IN RESPONSE TO WOUNDING AND TENSILE-STRESS

To identify controlling cis acting promoter regions in the B. napus ex tA extensin gene, expression in transgenic tobacco of 5' -159, -433, - 664, -789 and -940 bp promoter truncations linked to the uidA (B-glucu ronidase) reporter coding sequence were analysed. The -159 and -433 bp truncations directed non specific expression in all cell types within the plant. An activator region which increased expression levels 10 f old in all cell types was located between -159 to -433 bp. A repressor region was found between -664 to -789 bp; removal of this region resu lted in a 15 fold increase in expression. Histochemical analysis showe d that transgenics containing the -664, -789 and -940 bp truncations d irected expression of the fusion gene only in the phloem. A negative r egulatory region located between -433 to -664 bp repressed expression in non-phloem cell types. In areas of the plant subject to tensile str ess, the repression exerted by the negative regulatory region was over come, allowing expression in all cell types. The quantitative represso r and activator regions which controlled absolute expression levels in all cell types were seperate from the negative regulatory region whic h controlled cell type specific expression in response to tensile stre ss. A wound responsive region was found to be located between -940 to -3500 bp. Thus, the extA gene is under complex control, being regulate d by 4 sets of positively and negatively acting cis regions, which con trol wound inducibility, activation in response to tensile stress, and quantitative expression levels.