REGULATION OF AN ARABIDOPSIS OLEOSIN GENE PROMOTER IN TRANSGENIC BRASSICA-NAPUS

Progressive deletions of the 5'-flanking sequences of an Arabidopsis o leosin gene were fused to beta-glucuronidase (GUS) and introduced into Brassica napus plants using Agrobacterium-mediated transformation. Th e effect of these deletions on the quantitative level of gene expressi on, organ specificity and developmental regulation was assessed. In ad dition, the influence of abscisic acid (ABA), jasmonic acid (JA), sorb itol and a combined ABA/sorbitol treatment on gene expression was inve stigated. Sequences that positively regulate quantitative levels of ge ne expression are present between -1100 to -600 and -400 to -200 of th e promoter. In addition, sequences present between -600 and -400 down- regulate quantitative levels of expression. In transgenic B. napus pla nts, the oleosin promoter directs seed-specific expression of GUS whic h is present at early stages of seed development and increases through out seed maturation. Sequences present between -2500 and -1100 of the promoter are involved in modulating the levels of expression at early stages of embryo development. Histochemical staining of embryos demons trated that expression is uniform throughout the tissues of the embryo . Sequences involved in the response to ABA and sorbitol are present b etween -400 and -200. The induction of GUS activity by a combined ABA/ sorbitol treatment is additive suggesting that ABA is not the sole med iator of osmotically induced oleosin gene expression. A response to JA was only observed when the oleosin promoter was truncated to -600 sug gesting that the reported effect of JA on oleosin gene expression may be at a post-transcriptional level.