Effect of an enhanced CaMV 35S promoter and a fruit-specific promoter on UIDA gene expression in transgenic tomato plants

Two different promoters, a cauliflower mosaic virus (CaMV) 35S promoter wit h a 5'-untranslated leader sequence from alfalfa mosaic virus RNA4 (designa ted as CaMV 35S/AMV) and an E-8 fruit-ripening-specific. promoter, were com pared to evaluate their effects on expression of the uidA reporter gene in transgenic tomato plants. In order to generate sufficient numbers of transg enic tomato plants, both a reliable regeneration system and an efficient Ag robacterium transformation protocol were developed using 8-d-old cotyledons of tomato (Lycopersicon esculentum Mill. cv. Swifty Belle). Two sets of co nstructs, both derivatives of the binary vector pBI121, were used in transf ormation of tomato whereby the uidA gene was driven either by the CaMV 35S/ AMV or the E-8 fruit-ripening-specific promoter. Southern blot hybridizatio n confirmed the stable integration of the chimeric uidA gene into the tomat o genome. Fruit and leaf tissues were collected from TO and T-1 plants, and assayed for beta -glucuronidase (GUS) enzyme activity. As expected, both v egetative and fruit tissues of transgenic plants carrying the uidA gene und er the control of CaMV 35S/AMV showed varying levels of GUS activity, while no expression was observed in vegetative tissues of transgenic plants carr ying the uidA gene driven by the E-8 promoter. All fruits from transgenic p lants produced with both sets of constructs displayed expression of the uid A gene. However, when this reporter gene was driven by the CaMV 35S/AMV, GU S activity levels were significantly higher than when it was driven by the E-8 fruit-specific promoter. The presence/absence of the uidA gene in T-1 p lants segregated in a 3:1 Mendelian ratio.