DNA microarray analysis of Synechocystis sp. PCC 6803 cells under PSII and PSI light conditions

In the cyanobacterium Synechocystis sp. PCC 6803, expression of several genes such as psbA, psbD, psaAB, rbcLS and trxA is known to be largely affected by the redox state of photosynthetic electron transport. Redox regulation of mRNA levels is well-established, however, information is limited to photosynthetic genes so far. In this study, by using DNA microarray technology, we identified the whole set of genes regulated by photosynthetic electron transport in the genome of Synechocystis. Glucose-tolerant wild type strain was incubated with or without 10 m M 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) for 1 h. Total RNA was isolated from both cultures, labeled with fluorescent dye Cy3 or Cy5, mixed and hybridized with CyanoCHIP version 0.8 (TaKaRa). Triplicate experiments were performed under each of low light (20 m Em-2s-1) and high light (300 m Em-2s-1) conditions. About 400 ORFs were identified as redox responsive genes. By addition of DCMU, genes involved in photosynthetic electron transport (psb, psa, apc, cpc, pet) and some motility related genes were up-regulated. On the other hand, genes related to CO2 concentration (ccm, ndhF3D3, etc), translation (rps, rpl, etc), biosynthesis of amino acids, ATP synthesis (atp) and some heat shock genes (groESL, htpG, etc) were down-regulated. Furthermore, we examined changes in mRNA levels upon addition of 2,5-dibromo-3-methyl-6-isopropyl-benzoquinone (DBMIB) and by exposure to different light qualities (PSII and PSI light) using DNA microarray. Redox sensing mechanism of Synechocystis will be discussed based on these results.