Genetic evidence for the temperature-sensing ability of the membrane domain of the Bacillus subtilis histidine kinase DesK.

A decrease in environmental temperature leads to the synthesis of Delta5-unsaturated fatty acids in Bacillus subtilis by the fatty acid desaturase Des. Des is regulated by the two-component system DesKR. To understand the mechanism of cold signal perception and transduction by the membrane domain and the cytosolic domain of DesK, we expressed the cytosolic domain of DesK in trans under the control of a xylose-inducible promoter without the membrane domain. We performed growth experiments and a Northern blot analysis. Our results show that the kinase function of the cytosolic domain of DesK is temperature-independent, leading to a constitutive expression of the des gene. These findings support the conclusion that the membrane domain of DesK is the temperature-sensing element of the two-component system.