Evaluation of Constitutive Promoters for Gene Expression in Dendrobium Protocorms and Flowers

Abstract

Actively dividing protocorms of Dendrobium Jaquelyn Thomas orchid were produced on VW medium and transferred to 1/2 MS medium before subjecting to particle bombardment to evaluate the promoter efficiency. Three different constitutive promoters, rice Act-1, CaMV35S, and maize Ubi-1, were determined for the efficiency to control spatial transgene expression in protocorms and sepal tissues of Dendrobium orchid. Each promoter was fused to β-glucuronidase (uid A) gene and nos terminator in the plant expression vectors including pActin1-D, pAHC27, and p2K7. The plasmid vectors were individually bombarded into protocorms and fresh sepals of Dendrobium. Transient gus gene expression was assayed after 3 days of bombardment. The results demonstrated that all tested promoters could drive gus gene expression in the orchid protocorms at different levels. Ubi-1 promoter conferred the most efficient promoter in protocorms giving the highest level of gus gene expression, whereas GUS activity was distinctly observed under the control of Act-1 and CaMV35S in the Dendrobium sepal tissues. Both Act-1 and CaMV35S promoters performed well in the vascular tissue of flower as opposed to the Ubi-1 promoter that did not perform in flower.