Light inducible and tissue-specific expression of a chimeric mouse metallothionein cDNA gene in tobacco

A metallothionein cDNA was placed in sense or antisense orientation under the transcriptional control of a light-regulated promoter and the 3′ flanking region from a pea ribulose bisphosphate carboxylase small subunit gene and introduced into Nicotiana tabacum by Agrobacterium-mediated transformation. Regenerated plants with the sense construct showed expression of metallothionein (MT) in a light-regulated, tissue-specific manner. Genetic analysis of R1 and R2 progeny showed inheritance of the kanamycin resistance marker gene as a dominant Mendelian trait. Transgenic young seedlings with rbcS(ribulose bisphosphate carboxylase small subunit)-MT construct showed slightly more tolerance to cadmium stress than did untransformed control seedlings. In addition to these studies, a comparison was made of the relative strengths of the CaMV 35S, rbcS, and mouse metallothionein promoters in plants. The MT promoter was virtually inactive in plants, even those treated with Cd.