Journal Article

Plastidic RNA polymerase σ factors in <i>Arabidopsis</i>

Kengo Kanamaru, Makoto Fujiwara, Motoaki Seki, Takeshi Katagiri, Masanobu Nakamura, Nobuyoshi Mochizuki, Akira Nagatani, Kazuo Shinozaki, Kan Tanaka and Hideo Takahashi

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 40, issue 8, pages 832-842
Published in print January 1999 | ISSN: 0032-0781
Published online January 1999 | e-ISSN: 1471-9053 | DOI:
Plastidic RNA polymerase σ factors in Arabidopsis

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry


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In plant cells, plastid DNA is transcribed by at least two types of RNA polymerase, plastid-encoded RNA polymerase (PEP) and nuclear-encoded RNA polymerase (NEP). PEP is homologous to eubacterial transcription machinery, but its regulatory subunit, sigma (σ) factor, is not encoded on the plastid DNA. We previously cloned the three nuclear-encoded sigma factor genes from Arabidopsis thaliana and designated them as sigA, sigB, and sigC. By means of RFLP mapping, sigA and sigB were mapped on chromosome I and sigC on the chromosome III. Based on comparison of the genomic structure of the three sig genes, intron sites in the 3′ half of the genes were shown to be identical between sigB and sigC but divergent in sigA, consistent with the phylogenetic relevance of the three gene products. A transient expression assay of GFP fusions in Arabidopsis protoplasts showed that the N-termini of all three sig gene products functioned as chloroplast-targeting signals. We also constructed transgenic Arabidopsis lines harboring the sigA-promoter or the sigB-promoter uidA fusion. Both the sigA- and sigB-promoters were similarly activated at cotyledons, hypocotyls, rosette leaves, cauline leaves, sepals, and siliques but not at roots, seeds, or other flower organs. In addition, the two promoters were repeatedly activated in young seedlings under continuous light, possibly in an oscillated fashion.

Keywords: Arabidopsis thaliana; Chloroplast; Plastid-encoded RNA polymerase (PEP); Sigma factor

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Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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