[Characteristics of steroid metabolism in transgenic Nicotiana tabacum plants bearing the CYP11A1 cDNA of cytochrome P450(SCC) from the bovine adrenal cortex].

In the mitochondria of animal steroidogenic tissues, cytochrome P450(SCC), encoded by the CYP11A1 gene, catalyzes the conversion of cholesterol into pregnenolone - the general precursor of all steroid hormones. In this work, we study the steroid metabolism in transgenic tobacco plants carrying the CYP11A1 cDNA cytochrome P450(SCC)from the bovine adrenal cortex. The transgenic plants under investigation markedly surpass the control wild-type plants by size and are characterized by a shortened period of vegetative growth (by rapid flowering); their leaves contain pregnenolone - the product of a reaction catalyzed by cytochrome P450(SCC). The level of progesterone in transgenic tobacco leaves is higher than in the control plants of the wild type. The seeds of the transgenic plants contain less (24R)-brassinosteroids than the wild-type tobacco plants. The results obtained indicate that the synthesis of an active P450(SCC) cytochrome in transgenic Nicotiana tabacum plants has a profound effect on steroid metabolism and is responsible for the specific phenotypic features of transgenic plants bearing CYP11A1 cDNA.

[Construction and characteristics of transgenic tobacco Nicotiana tabacum L. plants expressing CYP11A1 cDNA encoding cytochrome P450scc].

In steroidogenic animal tissues cytochrome P450scc catalizes the conversion of cholesterol into pregnenolone, a common metabolic precursor of all steroid hormones. To study the possibility of functioning of mammalian cytochrome P450scc in plants and the mechanism of its integration in the plant steroidogenic system, transgenic plants of tobacco Nicotiana tabacum L. were developed carrying cDNA of CYP11A1 encoding cytochrome P450scc of bovine adrenal cortex. Pregnenolone, a product of the reaction catalyzed by cytochrome P450scc, was discovered in the steroid-containing fraction of transgenic plants. Transgenic plants are characterized by a reduced period of vegetative development (early flowering and maturation of bolls) and increased productivity. The contents of soluble protein and carbohydrates in leaves and seeds of transgenic plants are essentially higher than the contents of these components in leaves and seeds of control plants.