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Leaf-specifically expressed genes for polypeptides destined for chloroplasts with domains of sigma 70 factors of bacterial RNA polymerases in Arabidopsis thaliana

Isono, K., Shimizu, M., Yoshimoto, K., Niwa, Y., Satoh, K., Yokota, A., Kobayashi, H.
Proceedings of the National Academy of Sciences of the United States of America 1997 v.94 no.26 pp. 14948-14953
Arabidopsis thaliana, complementary DNA, binding proteins, DNA-directed RNA polymerase, nucleotide sequences, amino acid sequences, structural genes, chromosome mapping, gene expression, leaves, messenger RNA, recombinant DNA, animal proteins, cytochemistry, chloroplasts, fluorescence, transgenic plants, Nicotiana tabacum
Genes for sigma-like factors of bacterial-type RNA polymerase have not been characterized from any multicellular eukaryotes, although they probably play a crucial role in the expression of plastic photosynthesis genes. We have cloned three distinct cDNAs, designated SIG1, SIG2, and SIG3, for polypeptides possessing amino acid sequences for domains conserved in sigma 70 factors of bacterial RNA polymerases from the higher plant Arabidopsis thaliana. Each gene is present as one copy per haploid genome without any additional sequences hybridized in the genome. Transient expression assays using green fluorescent protein demonstrated that N-terminal regions of the SIG2 and SIG3 ORFs could function as transit peptides for import into chloroplasts. Transcripts for all three SIG genes were detected in leaves but not in roots, and were induced in leaves of dark-adapted plants in rapid response to light illumination. Together with results of our previous analysis of tissue-specific regulation of transcription of plastic photosynthesis genes, these results indicate that expressed levels of the genes may influence transcription by regulating RNA polymerase activity in a green tissue-specific manner.