Variable patterns of expression of luciferase in transgenic tobacco leaves

A carboxyl-terminally modified firefly luciferase, encoded as a gene fusion to the neomycin phosphotransferase gene (which confers kanamycin resistance), was found to be enzymatically active for both enzymes when expressed in bacteria and in transgenic plants. A military-type starlight vision system was used to conveniently analyze the pattern of gene expression in transgenic tobacco plant leaves. Transgenic tobacco plants which expressed luciferase uniformly in all areas of the leaf, and assays for luciferin, demonstrated that luciferin rapidly penetrates all regions of a tobacco leaf in at least two dimensions. Depending on the test gene structure or, presumably, on the transferred DNA (T-DNA) insertional context, other transgenic plants were obtained that expressed luciferase with a wide range of nonuniform patterns from nominally the same cauliflower mosaic virus 35S promoter. For instance, the veins can be dark, while only the interveinal regions of the leaf lamina glow, or only the small capillary veins glow, or only the major veins glow. Local and/or systemic induction in response to wounding was also demonstrated.