TISSUE-SPECIFIC AND LIGHT REGULATION OF A LARCH RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE PROMOTER IN TRANSGENIC TOBACCO

A chimeric gene composed of an eastern larch (Larix laricina (Du Roi) K. Koch) ribulose-1,5-bisphosphate carboxylase (RbcS) promoter linked to the beta-glucuronidase (GUS) coding sequence was transferred to tobacco (Nicotiana tabacum (L.)) via Agrobacterium tumefaciens transformation. Based on GUS activity the larch RbcS promoter functioned in an organ-specific and light-regulated manner. Histochemical analysis revealed high levels of GUS activity in photosynthetically active tissues and low or undetectable activity in xylem and root tissues. Fluorometric analysis of GUS activity demonstrated that the larch RbcS promoter was expressed at a 10-fold higher level in leaf blades than in root tissue. Light-grown transgenic plants expressed GUS at a two-fold higher level than dark grown individuals. These results suggest evolutionary conservation of tissue-specific RbcS promoter activity between gymnosperms and angiosperms but only weak conservation of the transduction mechanism for light regulation.