Constitutive Promoters Available for Transgene Expression Instead of CaMV 35S RNA Promoter : Arabidopsis Promoters of Tryptophan Synthase Protein β Subunit and Phytochrome B

To search for strong promoters that confer constitutive expression of transgenes, we evaluated the promoters of an Arabidopsis tryptophan synthase protein β subunit gene (PTSB1) and a phytochrome B gene (PPHYB) as alternatives to the 35S RNA promoter (P35S) of Cauliflower mosaic virus. Characteristics of the Soybean chrolotic mottle virus promoter (PNCR) were also studied for comparison. In transgenic calli, GUS gene fused with PTSB1, PPHYB and PNCR showed 50% or more of the activity of P35S. To drive the NPTII marker gene, the four promoters were similarly useful. In generated transgenic tobacco plants, both PTSB1 and PPHYB were active in all tissues tested, and superior to P35S in the leaves. The four promoters differed slightly in their tissue-specific expression, but were expressed constitutively, indicating that PTSB1 and PPHYB as well as PNCR are useful as strong and constitutive promoters as alternatives to P35S for genetic manipulation of plants.