Intron-mediated enhancement of the banana bunchy top virus DNA-6 promoter in banana (Musa spp.) embryogenic cells and plants

Intron-containing fragments derived from the 5' untranslated regions of the maize ubi1, maize adh1, rice act1 and sugarcane rbcS genes were tested for their enhancing effects on the banana bunchy top virus DNA-6 promoter (BT6 .1) in banana (Musa spp. cv. Bluggoe) embryogenic cells. The rice act1 and maize ubi1 introns provided the highest levels of intron-mediated enhanceme nt of GUS expression, increasing native BT6.1 promoter activity by about 30 0-fold and 100-fold, respectively. The sugarcane rbcS intron increased expr ession about tenfold, whereas the adh1 intron had no significant effect. In regenerated transgenic banana plants, the ubi1 intron significantly enhanc ed BT6.1 promoter activity to levels similar to that of the CaMV 35 S promo ter and did not appear to affect the tissue specificity of the promoter.