Studies on the structure and expression of chloroplast genes

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The genes which are encoded by chloroplast DNA was located on tobacco chloroplast DNA physical map, and cloned into the plasmids. Among them. the nucleotide sequences of genes for <alpha> . <beta> and <epsilon> subunits of ATPase were determined. The nucleotide sequences of transfer RNA genes for glycine, arginine, serine and glutamine were also determined. It is interesting that tRNA for glycine gene contains a 691-base-pair intron located in the D stem. Sequence of the junctions between a large inverted repeat and single-copy regions in the DNA was analyzed.Chloroplast DNA was also isolated from young rice leaves. The DNA was analyzed by several restriction endonuclease patterns and the size of the DNA was estimated to be 130 kbp. A physical map of the DNA for Sal 1, Pst 1 and Pvu 2 has been constructed based on double digestion data and Southern hybridization.The location of several genes responsible for photosynthesis was also determined on rice chloroplast DNA using tobacco DNA fragments containing those genes as probes. Since the yield of chloroplast DNA from rice leaves is very low. rice chloroplast DNA fragments generated by the digestion with Bam HI and Pst 1 were cloned into the plasmids.Gene expression of the large subunit of Rubisco and 32KD protein was studied. It was shown that a quarter of mRNAs for these proteins exists as the untranslatable form in chloroplasts. This evidence suggests the existence of regulatory mechanism at the level of translation.