Activity of elements from the tobacco cryptic promoter, tCUP , in conifer tissues

Summary Cryptic gene regulatory elements are inactive at their native locations in the genome but are fully functional when positioned adjacent to genes in transgenic plants. Although they are widespread among diverse organisms, they have not yet been described in gymnosperms. tCUP is a strong constitutive cryptic promoter from tobacco that harbors transcriptional enhancers, à TATA-less core promoter, and a translational enhancer, tCUP is active in all conifer species tested including white spruce, white pine, Loblolly pine, larch, and Douglas fir. The tCUP enhancers are fully active in white spruce in combination with the tCUP or 35S core promoters. The core promoter is proportionally stronger in white spruce than in angiosperms. It is dependent on an Inr sequence at the transcription start site; however, a cryptic core promoter was found in the tCUP leader sequence that harbors another potential Inr site. The leader sequence is essential for full tCUP activity in white spruce and it can be combined with other promoters, such as the 35S promoter, to elevate activity further. Stable and constitutive expression of tCUP is demonstrated in transgenic trees of white spruce. tCUP provides an alternative system for the expression of cloned genes in conifer species.