Phytochrome control of plastid mRNA in mustard (Sinapis alba L.).

The steady-state levels of plastid RNA sequences in dark-grown and light-grown mustard (Sinapis alba L.) seedlings have been compared. Total cellular RNAs were labeled in vitro with (32)P and hybridized to separated restriction fragments of plastid DNA. Cloned DNA fragments which encode the large subunit (LS) of ribulose-1,5-bisphosphate carboxylase [3-phospho-D-glycerate carboxylase (dimerizing), EC 4.1.1.39] and a 35,000 plastid polypeptide were used as probes to assess the levels of these two plastid mRNAs. The 1.22-kilobase-pair mRNA for the 35,000 polypeptide is almost undetectable in dark-grown seedlings, but is a major plastid mRNA in light-grown seedlings. The hybridization analysis of RNA from seedlings which were irradiated with red and far-red light indicates that the level of this mRNA, but not of LS mRNA, is controlled by phytochrome.