Yellow mutations alter chloroplast ribosomal proteins in Chlamydomonas reinhardii.

Ribosomes and ribosomal proteins from wild-type and three yellow mutants of Chlamydomonas reinhardii were analyzed and compared by two-dimensional gel-electrophoresis. Mixotrophycally grown mutants differ from wild-type cells in lowered chlorophyll content. Analytical ultracentrifugation analysis of cell extracts showed a reduced amount of 70S ribosomes and an increased level of 50S subunits in mutants y-27 and y-28. Two-dimensional gel electrophoresis indicated considerable alterations in the protein composition of 70S ribosomes of the mutants. Two proteins of 70S ribosomes were altered in the y-27 and y-28 mutants. Two proteins were absent from the electrophoretograms of the yellow-76 mutant and seven proteins were present in lowered concentrations. The mutations are inherited in a non-Mendelian manner. The protein alterations in 70S ribosome are most probably localized in the chloroplast DNA.