Abstract
In cyanobacteria, small LuxR-type transcriptional regulators having three cysteines in their C-termini are highly conserved. We found that a small LuxR-type regulator, Ssl0564, in Synechocystis sp. PCC 6803 regulates the expression of a set of genes such as ndhD2 encoding a subunit of NAD(P)H dehydrogenase, rpe encoding pentose phosphate epimerase, and chlL, chlN, and chlB encoding subunit of light-independent protochlorophyllide reductase. Northern blot analysis showed that the expression of these target genes is regulated in response to changes of light intensity and this regulation is dependent on the redox state of acceptor side of photosystem I. When photosynthetic electron transport activity is lowered, cysteine residues in Ssl0564 are oxidized, leading to the up- or down-regulation of the target genes. We are going to identify cysteine residue(s) involved in redox sensing by the characterization of cysteine variants.
