An RNA helicase, CrhR, regulates the low-temperature-inducible expression of heat-shock genes groES, groEL1 and groEL2 in Synechocystis sp. PCC 6803

Microbiology (Reading). 2010 Feb;156(Pt 2):442-451. doi: 10.1099/mic.0.031823-0. Epub 2009 Nov 19.


The crhR gene for RNA helicase, CrhR, was one of the most highly induced genes when the cyanobacterium Synechocystis sp. PCC 6803 was exposed to a downward shift in ambient temperature. Although CrhR may be involved in the acclimatization of cyanobacterial cells to low-temperature environments, its functional role during the acclimatization is not known. In the present study, we mutated the crhR gene by replacement with a spectinomycin-resistance gene cassette. The resultant DeltacrhR mutant exhibited a phenotype of slow growth at low temperatures. DNA microarray analysis of the genome-wide expression of genes, and Northern and Western blotting analyses indicated that mutation of the crhR gene repressed the low-temperature-inducible expression of heat-shock genes groEL1 and groEL2, at the transcript and protein levels. The kinetics of the groESL co-transcript and the groEL2 transcript after addition of rifampicin suggested that CrhR stabilized these transcripts at an early phase, namely 5-60 min, during acclimatization to low temperatures, and enhanced the transcription of these genes at a later time, namely 3-5 h. Our results suggest that CrhR regulates the low-temperature-inducible expression of these heat-shock proteins, which, in turn, may be essential for acclimatization of Synechocystis cells to low temperatures.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acclimatization / genetics
  • Bacterial Proteins / biosynthesis
  • Bacterial Proteins / genetics
  • Blotting, Northern
  • Chaperonin 10 / genetics
  • Chaperonin 60 / genetics
  • Cold Temperature
  • Gene Expression Regulation, Bacterial*
  • Genetic Complementation Test
  • Heat-Shock Proteins / biosynthesis
  • Heat-Shock Proteins / genetics*
  • Heat-Shock Response / genetics
  • Mutation
  • Oligonucleotide Array Sequence Analysis
  • RNA Helicases / genetics
  • RNA Helicases / metabolism*
  • Synechocystis / enzymology*
  • Synechocystis / physiology


  • Bacterial Proteins
  • Chaperonin 10
  • Chaperonin 60
  • Heat-Shock Proteins
  • RNA Helicases