The expression of foreign gene under the control of cauliflower mosaic virus 35s RNA promoter

Abstract

The promoter region of cauliflower mosaic virus (CaMV) 35s RNA was employed to construct an intermediate expression vector which can be used in Ti plasmid system of Agrobacterium tumefaciens. The original plasmid, which contains a polylinker between CaMV 35s RNA and its 3′ termination signal in pUC18 was modified to have another antibiotic resistance marker (kanamycin resistance gene Kmr) to facilitate the selection of recombinant with Ti plasmid. Octopine synthase (ocs) structural gene was inserted into this vector downstream of CaMV 35s RNA promoter. This chimaeric gene was introduced into integrative Ti plasmid vector pGV3850, and then transformed into Nicotiana tobaccum cells. A binary plasmid vector was also used to introduce the chimaeric gene into tobacco cells. In both cases, the expression of ocs gene was demonstrated. The amount of octopine was much more than the nopaline synthesized by nopaline synthase (nos) gene transferred at the same time with Ti plasmid vector. This demonstrated that CaMV 35s RNA promoter is stronger in transcriptional function than the promoter of nos in tobacco cells.