Functional analysis of the Rubisco large subunit (ε)N-methyltransferase promoter from tobacco and its regulation by light in soybean hairy roots

The ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) large subunit (LS) (ε)N-methyltransferase (Rubisco LSMT) catalyzes post-translational methylation of the ε-amino group of lysine-14 in the LS of Rubisco. The entire nucleotide sequence for the tobacco (Nicotiana tabacum) Rubisco LSMT (rbcMT-T) gene including the putative promoter region was recently reported, and sequence analysis of the promoter region revealed seven GT-1 motifs. The ability of several truncated rbcMT-T promoter fragments to confer light responsiveness to reporter gene expression in transgenic soybean (Glycine max) hairy roots was examined. Chimeric constructs consisting of the rbcMT-T promoter fused to a bacterial β-glucuronidase (GUS) reporter gene and transferred to soybean via Agrobacterium rhizogenes were evaluated. The rbcMT-T promoter fragments conferred expression of the reporter gene in transgenic hairy roots, callus, and cell suspension cultures based on histochemical and fluorometric GUS analyses. The results suggest a quantitative role for the number of GT-1 motifs in determining differential expression between light and dark conditions.