Genetics and molecular biology of plastids of higher plants : plastids in male gametes, mutation induction, nitroso - urea, plastid mutants, thylakoid proteins, plastid ribosome deficiency, pollen, chloroplast, photosynthesis, mitochondria
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In the majority of angiospermous species the plastids are excluded from the generative or sperm cells during the first pollen mitosis or during pollen development; this is the basis of the maternal inheritance of plastid genes. In a smaller group of species there is, however, an equal distribution of plastids during the first pollen mitosis. Consequently generative and sperm cells of these species contain numerous plastids, and there is biparental plastid inheritance. N-nitroso-N-methyl-urea and N-nitroso-N-ethyl-urea are chemicals potent for the induction of plastome mutations in higher plants (Antirrhinum, Lycopersicon, Helianthus, Saintpaulia). Our research group analyzed three mutants of Antirrhinum and Pelargonium: they proved to have specific defects in photosystem I or photosystem II and an associated loss (or marked decrease) in specific thylakoid proteins which are connected with the photosystems. In Pelargonium and Hordeum we found several plastome mutants which have no (or almost no) plastid ribosomes, but normal amounts of cytoplasmicribosomes. These mutants are very suitable tools for the study of the synthetic capacity of the plastidal protein synthesizing system. Using these mutants a number of plastid components have been characterized which are synthesized on cytoplasmic ribosomes and then transported into the plastids. On the other hand, four protein complexes have been proved to be missing in the mutant deficient plastid ribosomes, because some of their polypeptides are normally synthesized on plastid ribosomes and are consequently not formed in these mutants. These are ribulose-1, 5-biphosphate carboxylase/oxygenase, plastidal coupling factor CF1, and the protein complexes for photosystem I and II.