TY - JOUR
T1 - Characterization of single and double inactivation strains reveals new physiological roles for group 2 sigma factors in the cyanobacterium Synechocystis sp. PCC 6803
AU - Pollari, Maija
AU - Gunnelius, Liisa
AU - Tuominen, Ilona
AU - Ruotsalainen, Virpi
AU - Tyystjärvi, Esa
AU - Salminen, Tiina
AU - Tyystjärvi, Taina
PY - 2008/8
Y1 - 2008/8
N2 - Cyanobacteria are eubacteria that perform oxygenic photosynthesis like plants. The initiation of transcription, mediated by the RNA polymerase holoenzyme, is the main determinant of gene regulation in eubacteria. The sigma factor of the RNA polymerase holoenzyme is responsible for the recognition of a promoter sequence. In the cyanobacterium Synechocystis sp. PCC 6803, the primary sigma factor, SigA, is essential for cell viability. The SigB, SigC, SigD, and SigE factors show significant sequence similarity with the SigA factor but are nonessential. In this study, we have used homology modeling to construct a three-dimensional model of Synechocystis RNA polymerase holoenzyme and all group 1 and 2 sigma factors. According to the models, the overall three-dimensional structures of group 1 and 2 sigma factors are similar, the SigB and SigD factors being the most similar ones. In addition, we have constructed a complete set of group 2 sigma factor double inactivation strains, DeltasigBC, DeltasigBD, DeltasigBE, DeltasigCD, DeltasigCE, and DeltasigDE. All double mutants grow well under standard conditions, but differences are observed in stress conditions. The transition from lag phase to exponential growth is slow in the DeltasigBD strain, and all strains lacking the SigD factor were found to be sensitive to bright light. Furthermore, all group 2 sigma factors were found to be involved in acclimation to salt- or sorbitol-induced osmotic stresses.
AB - Cyanobacteria are eubacteria that perform oxygenic photosynthesis like plants. The initiation of transcription, mediated by the RNA polymerase holoenzyme, is the main determinant of gene regulation in eubacteria. The sigma factor of the RNA polymerase holoenzyme is responsible for the recognition of a promoter sequence. In the cyanobacterium Synechocystis sp. PCC 6803, the primary sigma factor, SigA, is essential for cell viability. The SigB, SigC, SigD, and SigE factors show significant sequence similarity with the SigA factor but are nonessential. In this study, we have used homology modeling to construct a three-dimensional model of Synechocystis RNA polymerase holoenzyme and all group 1 and 2 sigma factors. According to the models, the overall three-dimensional structures of group 1 and 2 sigma factors are similar, the SigB and SigD factors being the most similar ones. In addition, we have constructed a complete set of group 2 sigma factor double inactivation strains, DeltasigBC, DeltasigBD, DeltasigBE, DeltasigCD, DeltasigCE, and DeltasigDE. All double mutants grow well under standard conditions, but differences are observed in stress conditions. The transition from lag phase to exponential growth is slow in the DeltasigBD strain, and all strains lacking the SigD factor were found to be sensitive to bright light. Furthermore, all group 2 sigma factors were found to be involved in acclimation to salt- or sorbitol-induced osmotic stresses.
KW - Acclimatization
KW - Amino Acid Sequence
KW - Bacterial Proteins/chemistry
KW - DNA-Directed RNA Polymerases/chemistry
KW - Light
KW - Models, Molecular
KW - Molecular Sequence Data
KW - Mutagenesis
KW - Osmotic Pressure
KW - Photosynthesis
KW - Protein Structure, Quaternary
KW - Sequence Alignment
KW - Sigma Factor/chemistry
KW - Sodium Chloride/pharmacology
KW - Synechocystis/genetics
UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000258184800047&KeyUID=WOS:000258184800047
U2 - 10.1104/pp.108.122713
DO - 10.1104/pp.108.122713
M3 - Article
C2 - 18539776
SN - 0032-0889
VL - 147
SP - 1994
EP - 2005
JO - Plant Physiology
JF - Plant Physiology
IS - 4
ER -