Development of chloro-etioplasts containing prolamellar bodies and steroidal saponins in suspension cultures ofNicotiana tabacum

Summary Chloroplasts of mixotrophically grown suspension cultures ofNicotiana tabacum possess the capability to build up para-crystalline prolamellar bodies (PLBs), resembling those ofAvena etioplasts. After dark incubation of light-grown tissue the plastids show PLBs, whose crystalline character depends on the duration of the dark incubation and the moment of the growth cycle, the chloroplasts are induced to build up PLBs. These chloro-etioplasts contain steroidal saponins closely related to the PLB-appearance. The relations between the PLB- and saponin occurrence, reported here and in previous papers, lead to the conclusion, that steroidal saponins are the building units of PLBs in many different plant species. A model for saponin synthesis and degradation, depending on dark- or light-incubation is discussed.