Amyloplast Formation in Cultured-Tobacco Cells II: Effects of Transcription/Translation Inhibitors on Accumulation of Starch.

Abstract

Differentiation of leucoplast-like plastids to amyloplasts occurred when BY-2 cultured tobacco (Nicotiana tabacum L.) cells were grown for 2 days in auxin-depleted culture medium containing cytokinin (benzyladenine, 1 mg/l). Development of the amyloplasts was inhibited by addition of various inhibitors, such as actinomycin D, cycloheximide, and chloramphenicol, indicating that amyloplast formation in BY-2 cells requires de novo synthesis of RNA and proteins in nucleo-cytoplasm and in organelles (i.e., plastids and mitochondria). Actinomycin D and cycloheximide inhibited accumulation of starch effectively and promptly irrespective of the timing of addition, while the inhibitory effect of chloramphenicol decreased as the time until addition grew longer. This indicates that continuous expression of cell-nuclear genes is necessary for amyloplast formation in BY-2 cells, whereas organelle gene expression becomes less necessary in the late phase of amyloplast development.