Abstract
When tobacco (Nicotiana tabacum L.) cultured cells (line BY-2) at the stationary phase were transferred to culture medium that contained cytokinin (benzyladenine) instead of auxin (2,4-dichlorophenoxyacetic acid), proplastids in the BY-2 cells were converted to amyloplasts within 48 h. The data obtained from in vitro transcription assays using isolated plastid-nucleoids (nuclei) strongly suggested that amyloplast formation in BY-2 cells was accompanied by changes in the transcriptional activities of plastid genes.