Expression of strictosidine β-D-glucosidase cDNA from Catharanthus roseus, involved in the monoterpene indole alkaloid pathway, in a transgenic suspension culture of Nicotiana tabacum

Different transgenic cell lines of Nicotiana tabacum expressing strictosidine β-D-glucosidase cDNA from Catharanthus roseus were established following Agrobacterium tumefaciens infection. The fresh weight and protein levels did not appear to be affected by the gene insertion performed, and in several instances these seemed to be boosted. Regarding strictosidine β-D-glucosidase activity (SGD, EC 3.2.1.105) in some of the cell lines, this seemed growth associated but in others it appeared steady during growth, suggesting a continuous activation of the inserted gene cassette triggered by the CaM35S promoter, showing maximum values of ca. 170 pkat·mg–1 protein following incubation of crude protein extracts. Liquid nutrient medium failed to show any enzyme activity and lacked proteins, indicating that the gene product was not released into the medium. Molecular data showed, as seen in C. roseus cells, that SGD activity was associated with a protein aggregate of a size of 650 kDa, and this was absent in control and samples of the transgenic lines which failed to show SGD activity.