The histidine kinase Hik34 is involved in thermotolerance by regulating the expression of heat shock genes in synechocystis.
Histidine kinases (Hiks) in Synechocystis sp. PCC 6803 are involved in the transduction of signals associated with various kinds of environmental stress. To examine the potential role in thermotolerance of Hiks, we used genome microarray analysis to screen a Hik knockout library for mutations that affected the expression of genes for heat shock proteins. Mutation of the hik34 gene enhanced the levels of transcripts of a number of heat shock genes, including htpG and groESL1. Overexpression of the hik34 gene repressed the expression of these heat shock genes. In addition, the cells with a mutant gene for Hik34 (DeltaHik34 cells) survived incubation at 48 degrees C for 3 h, while wild-type cells and cells with mutations in other Hiks were killed. However, mutation of the hik34 gene had only an insignificant effect on the global expression of genes upon incubation of the mutant cells at 44 degrees C for 20 min. Quantitative two-dimensional gel electrophoresis revealed that levels of GroES and HspA were elevated in DeltaHik34 cells after incubation of cells at 42 degrees C for 60 min. We overexpressed recombinant Hik34 protein in Escherichia coli and purified it. We found that the protein was autophosphorylated in vitro at physiological temperatures, but not at elevated temperatures, such as 44 degrees C. These results suggest that Hik34 might negatively regulate the expression of certain heat shock genes that might be related to thermotolerance in Synechocystis.
Suzuki
Iwane
I
Division of Cellular Regulation, National Institute for Basic Biology, Myodaiji, Okazaki 444-8585, Japan. iwanes6803@biol.tsukuba.ac.jp
Kanesaki
Yu
Y
Hayashi
Hidenori
H
Hall
John J
JJ
Simon
William J
WJ
Slabas
Antoni R
AR
Murata
Norio
N
D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D000458:Cyanobacteria / Q000201:enzymology; D017931:DNA Primers; D015180:Electrophoresis, Gel, Two-Dimensional; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D015723:Gene Library; D005822:Genetic Vectors; D006360:Heat-Shock Proteins / Q000235:genetics*; D000071677:Histidine Kinase; D006706:Homeostasis; D016296:Mutagenesis; D020411:Oligonucleotide Array Sequence Analysis; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D013045:Species Specificity; D046939:Synechocystis / Q000201:enzymology* / Q000235:genetics; D013696:Temperature
D001426:Bacterial Proteins; D017931:DNA Primers; D006360:Heat-Shock Proteins; D011494:Protein Kinases; D000071677:Histidine Kinase