Promoters derived from banana bunchy top virus DNA-1 to-5 direct vascular-associated expression in transgenic banana (Musa spp.)

The intergenic regions of banana bunchy top virus (BBTV) DNA-1 to -5 were fused to the green fluorescent protein (GFP) and uidA reporter genes and assessed for promoter activity in transgenic banana (Musa spp. cv. Bluggoe). Promoter activity associated with the BBTV-derived promoters was transgene dependent with greatest activity observed using the GFP reporter. The BBTV promoters (BT1 to BT5) directed expression primarily in vascular-associated cells, although levels of activity varied between individual promoters. Promoters BT4 and BT5 directed the highest levels of GFP expression, while activity from BT1, BT2 and BT3 promoters was considerably weaker. Intron-mediated enhancement, using the maize polyubiquitin 1 (ubi1) intron, generated a significant increase in GUS expression directed by the BBTV promoters in transgenic plants.