Promoters derived from banana bunchy top virus-associated components S1 and S2 drive transgene expression in both tobacco and banana

Potential promoter regions of the Banana bunchy top virus (BBTV)-associated DNA components S1 and S2 were fused to the beta -glucuronidase reporter ge ne and assessed for activity in both tobacco (Nicotiana tabacum cv. Xanthi) and banana (Musa spp. cv. Bluggoe). Transient assays indicated that all th e S1- and S2-derived promoters were active and had greater expression in to bacco than banana. In stably transformed tobacco and banana, the S1- and S2 -derived promoters directed expression in root meristems and trichomes. The S1 promoter was also expressed in the vascular tissue of leaves and roots, while both the S1 and S2 promoters were active in tobacco leaf trichomes a nd pollen. In banana, expression was significantly enhanced by the inclusio n of the maize polyubiquitin intron 3' to the promoter. Interestingly, ther e was some evidence to indicate that S1 promoter fragments containing part of the open reading frame at the 5' end of the promoter had enhanced activi ty, suggesting that promoter elements may not be confined to the non-coding region.