The complete nucleotide sequence (134,525 bp) of the chloroplast genome from rice (Oryza sativa L.) contains four rRNA genes, 30 tRNA genes, and over 100 genes that encode proteins. However, expression of only a few of these genes, namely psbA, rbcL, and atpB/E, has been detected. We constructed the complete transcription map of rice chloroplast DNA by Northern hybridization of total RNA from rice seedlings, using subclones from a clone bank of rice chloroplast DNA as probes. Approximately 90% of the chloroplast genome was transcribed, as detected by a non-radioactive hybridization system. Most of the genes on the chloroplast DNA are organized as clusters and are co-transcribed as long primary transcripts. We identified 16 polycistronic transcripts from the rice chloroplast genome. Furthermore, the genes for components of photosystems I and II, the gene for the large subunit of RuBisCO, the genes for ATPase, the genes for components of the cytochrome complex, and the rRNA genes were expressed at the highest levels.
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