A STUDY OF DIFFERENT (CAMV 35S AND MAS) PROMOTER ACTIVITIES AND RISK ASSESSMENT OF FIELD USE IN TRANSGENIC RAPESEED PLANTS

Gene fusions between the beta-glucuronidase (GUS) reporter gene and th e promoters of the cauliflower mosaic virus 35S RNA transcript (CaMV 3 5S) and the mannopine synthase (mas) genes were introduced into rapese ed varieties via Agrobacterium-mediated transformation. Fluorometric a ssay of beta-glucuronidase activity indicated different expression pat terns for the two promoters. In seedlings, the CaMV 35S promoter had m aximum activity in the primary roots, while the mas promoter was most active in the cotyledons. Etiolated seedlings cultured in the dark sho wed reduced activity of the mas promoter. Before vernalization at the rosette stage, both promoters were more active in older plant parts th an in younger ones. At this stage the highest activity was recorded in cotyledons. After the plants had bolted reduced promoter function was detected in the upper parts of the transformed plants. Both promoters were found to be functional in the majority of the studied organs of transgenic rapeseed plants, but the promoter activity varied considera bly between the organs at different developmental stages. The ability of pollen to transfer the introduced genes to other varieties and rela ted species (e.g. Brassica napus and Diplotaxus muralis) by cross-poll ination was studied in greenhouse experiments, and field trials were c arried out to estimate the distance for biologically - relevant gene d ispersal. In artificial crossing, the introduced marker gene was trans ferable into other varieties of Brassica napus. In field trials, at a distance of I metre from the source of transgenic plants, the frequenc y of an outcrossing event was relatively high (10(-3)). Resistant indi viduals were found at 16 and 32 metres from the transgenic pollen dono rs, but the frequency of an outcrossing event dropped to 10(-5).