Light Regulation of Plastid Gene Expression during Chloroplast Biogenesis in Barley; Evidence for Regulation of Translation and Post-Transcriptional Determination of mRNA Levels

Plastid Development in Pisum sativum Leaves during Greening

“…Our understanding of the regulation of the two most prominent nuclear encoded chloroplast polypeptides, the SSU3 and LHCP, has increased during the last years due to the work of several research groups. As with all nuclear encoded plastid proteins whose amino acid sequences have been described, SSU and LHCP are synthesized as precursor molecules on cytoplasmic ribosomnes and their primary translation products possess aminoterminal extensions (7) In this line of consecutive events, well established for these two polypeptides, several different points of regulatory control can be easily imagined: regulation at the level of transcription; RNA stability; regulation of translation; precursor stability in the cytosol; rate and specificity ofuptake; processing ofthe imported precursors; assembly in the presence ofthe corresponding factors; and rate of degradation inside the plastid (5,12,22).In …”

“…When a stoichiometric surplus of SSU or LHCP is synthesized in the cytosol and imported into the chloroplast, unassembled polypeptides are rapidly degraded (1,2,28). In this line of consecutive events, well established for these two polypeptides, several different points of regulatory control can be easily imagined: regulation at the level of transcription; RNA stability; regulation of translation; precursor stability in the cytosol; rate and specificity ofuptake; processing ofthe imported precursors; assembly in the presence ofthe corresponding factors; and rate of degradation inside the plastid (5,12,22).…”