DNA-binding and transcription characteristics of three cloned sigma factors from mustard (Sinapis alba L.) suggest overlapping and distinct roles in plastid gene expression.
We have isolated and studied the cloned sigma factors SASIG1-3 from mustard (Sinapis alba). In functional analyses using both promoter and factor mutants, the three recombinant proteins all had similar basic properties but also revealed differences in promoter preference and requirements for single nucleotide positions. Directed muta- genesis of SASIG1 identified critical residues within the conserved regions 2.4 and 4.2 necessary for binding of the -10 and -35 promoter elements, respectively. SASIG1 and 2, but not SASIG3, each have a typical region 2.5 for binding of the extended -10 promoter element. SASIG3 has a pro-sequence reminiscent of sigma K from Bacillus subtilis, suggesting that proteolytic cleavage from an inactive precursor is involved in the regulation of plastid transcription. In addition, SASIG2 was found to be more abundant in light-grown as compared to dark-grown mustard seedlings, while the converse was true for SASIG3.
Homann
Anke
A
Plant Cell Physiology and Molecular Biology, University of Bochum, Germany.
Link
Gerhard
G
D000595:Amino Acid Sequence; D001665:Binding Sites; D018744:DNA, Plant; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D009149:Mustard Plant / Q000737:chemistry*; D016297:Mutagenesis, Site-Directed; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018087:Plastids / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D018744:DNA, Plant; D010940:Plant Proteins; D011994:Recombinant Proteins; D012808:Sigma Factor