Expression of a Brassica napus extensin gene in the vascular system of transgenic tobacco and rape plants.

The organs and tissues where the Brassica napus extA extensin gene is expressed have been identified. The extA gene with 3.75 kb of 5' flanking sequence was transferred to tobacco via disarmed Agrobacterium tumefaciens vectors and transgenic plants regenerated. The gene was found to be inactive in transgenic tobacco leaf, but was active as measured by RNA transcript assays in both stem and root tissues. To determine the cell-specific expression pattern of the extA gene, a promoter-reporter gene fusion construct was made consisting of 1.0 kb of 5' extA sequence fused to the coding region of the glucuronidase (GUS) gene. This fusion construct was introduced into B. napus via Agrobacterium rhizogenes, and expression of GUS in transgenic rape hairy roots was examined. GUS activity was only seen in the vascular tissues of the rape root, and was found to be specifically localised in the phloem.