Stress response of genes encoding putative stress signaling molecules of Mycobacterium tuberculosis.

Mycobacterium tuberculosis possesses six genes (Rv0516c, Rv1364c, Rv1365c, Rv1904, Rv2638 and Rv3687c) encoding putative anti-sigma factor antagonists or stress signaling molecules (SSMs). We have previously shown that the products of these genes physically interact between themselves and with sigma factor SigF (encoded by Rv3286c) and anti-sigma factor RsbW (encoded by Rv3287c) in the yeast two-hybrid system. In order to understand whether ssms respond to stress, we analyzed the expression of these genes in M. tuberculosis exposed to stress at message level using real time RT-PCR. The results revealed that most ssms of M. tuberculosis responded to stress and Rv0516c was the most prominent one. Rv0516c showed elevated expression for NaCl, oxidative and starvation stresses and this was followed by Rv2638 which exhibited upregulation towards stationary phase, heat and oxidative stresses. While Rv1904 and Rv3687c responded significantly to cold and oxidative stresses, Rv1364c responded only to heat stress. Further, studies on the response of sigF and rsbW to stress revealed that only rsbW significantly responded to heat, cold, oxidative, starvation and anaerobic stresses. The response of ssms and rsbW to different stresses may be an indication for the stress activation and regulation of SigF by these molecules.