Quantification of mRNA in Chloroplasts of Chlamydomonas reinhardii: Equal Distribution of mRNA for a Soluble and a Membrane Polypeptide in Stroma and Thylakoids

摘要

The relative contents of the mRNAs were analyzed for the 32 kDa herbicide-binding protein and for the large subunit of ribulose-l,5-bisphosphate carboxylase in the membrane fraction and in the soluble fraction of chloroplasts from Chlamydomonas reinhardii. The presence of mRNA for the two proteins in both subchloroplast fractions was demonstrated by in vitro translation of isolated RNA in the reticulocyte lysate. The relative amounts of the two mRNAs were measured by hybridizations with cloned chloroplast DNA probes at two stages of the cell cycle. Both mRNAs were distributed in the same ratio between membrane and soluble fractions, about 75% of both mRNAs being in the membrane and 25% in the soluble fraction. Therefore, in chloroplasts the accumulation of mRNAs on thylakoid membranes does not reflect the final localization of soluble and membrane proteins