Regulation of Light-Harvesting Chlorophyll Protein Biosynthesis in Greening Seedlings

The biosynthesis of the chlorophyll a/b binding protein associated with photosystem II (LHC-II) was characterized during light-induced greening of etiolated barley (Hordeum vulgare [L.] cv Boone), maize (Zea mays [L.] Pioneer 3148), pea (Pisum sativum [L.] cv Progress 9), and soybean (Glycine max [L.] Merr. cv Ransom 2). Northern blot analysis revealed that pea LHC-II mRNA was present in dark-grown seedlings and accumulated rapidly within 1 hour following illumination with white light. In contrast, the accumulation of LHC-II mRNA was delayed in barley and soybean until 2 to 4 hours after illumination began. Single radial immunodiffusion analysis revealed that LHC-II polypeptides began to accumulate in all species between 4 and 8 hours although the protein was present in detectable levels at earlier times in certain species. In a pattern similar to the LHC-II protein accumulation, chlorophyll accumulated at increased rates between 4 and 8 hours of greening in all species following an initial delay. The absence of coordination between LHC-II mRNA and LHC-II protein accumulation that was clearly observed in pea suggested that transcription is not the factor that limits LHC-II complex formation during chloroplast development. The accumulation of chlorophyll and LHC-II protein appeared to coincide suggesting that chlorophyll biosynthesis may be a factor that limits LHC-II complex formation.