Effect of UTRs from TMV-RNA on the expression of foreign gene in transgenic plants

Abstract

To investigate the effects of 5′ and 3′ untranslated region (UTR) from tobacco mosaic virus (TMV) on expression of foreign genes, four plant-expression vectors pBG437, pBG438, pBG440 and pBG440ANOS containing expression cassettes ofGUS-NOS; Ω-GUS-NOS, Ω-GUS- 3′ UTR-NOS and Ω-GUS- 3′ UTR downstream of CaMV 35S promoter with double enhancer sequences respectively have been constructed. Results from a large number of transgenic tobacco plants show that the GUS activity of pBG440 transformed plants is the highest, being 5-fold that of pBG437 and 1.6-fold that of pBG438. Similar results have been obtained in transient expression by injection ofAgrobacterium tumefaciens harbouring these constructs intoN. benthamiana leaves. These results obtained at the whole plant level confirm the conclusion drawn from the transient expression studies in protoplast system that TMV-Ω fragment can be a translation enhancer and the 3′ UTR has a coordinate effect with Ω fragment to enhance foreign gene expression, but unlike the situation in transient expression in protoplast system, the 3′ UTR of TMV cannot act as a poly(A) tail nor as a transcription terminator in transgenic plants. The coordinate effect of 3′ UTR with Ω fragment needs the presence of a normal plant transcriptional terminator.