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In vivo recruitment analysis and a mutant strain without any group 2 σ factor reveal roles of different σ factors in cyanobacteria
Author(s) -
Koskinen Satu,
Hakkila Kaisa,
Gunnelius Liisa,
Kurkela Juha,
Wada Hajime,
Tyystjärvi Taina
Publication year - 2016
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.13214
Subject(s) - biology , cyanobacteria , rna polymerase , photosynthesis , synechocystis , sigma factor , mutant , strain (injury) , transcription factor , gene , acclimatization , protein subunit , transcription (linguistics) , botany , genetics , biochemistry , rna , bacteria , anatomy , linguistics , philosophy
Summary In eubacteria, replacement of one σ factor in the RNA polymerase ( RNAP ) holoenzyme by another one changes the transcription pattern. Cyanobacteria are eubacteria characterized by oxygenic photosynthesis, and they typically encode numerous group 2 σ factors that closely resemble the essential primary σ factor. A mutant strain of the model cyanobacterium S ynechocystis sp. PCC 6803 without functional group 2 σ factors (named as Δsig BCDE ) could not acclimate to heat, high salt or bright light stress, but in standard conditions Δsig BCDE grew only 9% slower than the control strain. One‐fifth of the genes in Δsig BCDE was differently expressed compared with the control strain in standard growth conditions and several physiological changes in photosynthesis, and pigment and lipid compositions were detected. To directly analyze the σ factor content of RNAP holoenzyme in vivo , a H is‐tag was added to the γ subunit of RNAP in Synechocystis and RNAPs were collected. The results revealed that all group 2 σ factors were recruited by RNAP in standard conditions, but recruitment of SigB and SigC increased in heat stress, SigD in bright light, SigE in darkness and SigB , SigC and SigE in high salt, explaining the poor acclimation of Δsig BCDE to these stress conditions.