Genetic control of plastid differentiation. 3 ultrastructure of plastids in different green revertant spots of the plastom mutant Pl-alb1 of Lycopersicon esculentum.

Reverse mutations in plastid DNA give rise to phenotypically different green spots on the white tissues of the homoplastic plastom mutant Pl-alb1. The structure of the plastids in one yellow-green, one green and one dark-green spot, each arising by independent reverse mutation, was studied by means of electron microscopy. Although the same revertant plastid types (type 1 with a weakly developed lamellar system; type 2 with vacuolized grana, and type 3 with a wild type-like structure were found in all three spots, variations in separation of Pl-alb1 and revertant plastids, and in the predominant revertant plastid type, were observed among the spots investigated. The revertant plastids of different phenotype occurred not only within one spot, but also within one cell. An hypothesis explaining this phenomenon is suggested.

Protein deficient chloroplast ribosomes in a yellow mutant of Chlamydomonas reinhardii.

Ribosomes and ribosomal proteins from wild-type and a yellow mutant of Chlamydomonas reinhardii were analyzed and compared by two-dimensional gel electrophoresis. The mixothrophically grown yellow-76 mutant differs from wild-type cells in lowered chlorophyll content and photosynthetic activity per chlorophyll unit. The latter is connected with the decreased activity of the ribulose-I,5-diphosphate-carboxylase enzyme. Analytical ultracentrifugation of cell extracts shows a normal amount of free 70S ribosomes and 50S subunit in the mutant cells. Two-dimensional gel electrophoresis shows considerable alterations in the protein composition of the 70S ribosomes of the mutant. Two proteins are absent from the electrophoretograms of the yellow-76 mutant, and seven proteins are present in reduced amounts. The genetical analysis shows a Mendelian pattern of inheritance, indicating that protein alterations presumably are localized in nuclear DNA.

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.