Cooperation of group 2 sigma factors, SigD and SigE for light-induced transcription in the cyanobacterium Synechocystis sp. PCC 6803.

A light-inducible sigma factor of RNA polymerase, SigD, can contributes to the light-induced transcription of psbA in the cyanobacterium Synechocystis sp. PCC 6803. Here, another light-induced sigma factor, SigE, was characterized together with SigD. Results indicated that SigE also contributes to light-induced transcription on the cpcBACD, psbA, petBD and psaAB promoters whose potential sequences are of the Escherichia coli sigma(70)-type. SigD and SigE interfere with each other's expression. A rhythmic expression, in which the periodic peak of SigE exhibits a 24-h interval according to the upcoming night, was observed at the protein level. The cooperation of group 2 sigma factors, SigD and SigE, for light-induced transcription was discussed.