Genetic Transformation of Solanum aculeatissimum

Abstract

Steroid saponins, aculeatiside A and aculeatiside B (Fig. 1), were isolated from the root of Solanum aculeatissimum Jacq. (Solanaceae) (Saijo et al. 1983). Natural steroid sapogenin (diosgenin), from tubers of Dioscorea species is used in the commercial production of steroid hormones, female steroid hormones, and steroidal pharmaceuticals (Ikegami 1981; Imada et al. 1981; Tal et al. 1984; Rokem et al. 1985). Since nuatigenin and isonuatigenin obtained by hydrolysis of aculeatiside A and aculeatiside B (Fig. 1) can be transformed into pregdienolone (Tschesche et al. 1964; Imada et al. 1981; Saijo et al. 1983), it is conceivable that S. aculeatissimum may be a more useful source of pregnane derivatives than the Dioscorea species (Imada et al. 1981). This plant also contains these steroid saponins at a high level; however, it had never been cultivated, and the properties and seasonal variations of growth and steroid saponin production, etc. were also not known. Results of an earlier experiment (Ikenaga et al. 1988a) showed that the content of steroid saponins per dry weight, aculeatiside A and B, increased as the plant grew, reached a peak in November, and decreased slightly in December when the aerial parts of the plant died. The yield of steroid saponins per plant increased in accordance with the rise in root dry weight until November, and then decreased by slow degrees (Table 1).