Abstract
In higher plants, plastids can differentiate depending on tissues and developmental stages. Using the suspension culture of Arabidopsis T87 cell line, we developed simple systems for differentiation of several types of plastids. In detail, proplastids in dark-grown T87 cells could be easily differentiated into amyloplasts or chloroplasts by change of light or phytohormone conditions. In the tobacco BY-2 system reported by Miyazawa et al. (1999), differentiation of amyloplasts was accompanied with the induction of nuclear-encoded genes related to starch synthesis. We have recently demonstrated in BY-2 cells that inhibition of plastid gene expression by specific inhibitors resulted in inhibition of amyloplast differentiation as well as repression of gene expression for nuclear starch-synthesis genes. This observation was partly reproduced in the T87 system established here. To assess the possibility that plastid differentiation could be regulated by plastid-derived signals, we started to analyze functions of some regulatory factors using transgenic approaches.
