LOV Histidine Kinase Modulates the General Stress Response System and Affects the virB Operon Expression in Brucella abortus.

Gabriela Sycz,Fernando A Goldbaum,Winslow R Briggs,Mariela Carmen Carrica,Roberto A Bogomolni,Tong-Seung Tseng,Gastón Paris

doi:10.1371/journal.pone.0124058

Abstract

Brucella is the causative agent of the zoonotic disease brucellosis, and its success as an intracellular pathogen relies on its ability to adapt to the harsh environmental conditions that it encounters inside the host. The Brucella genome encodes a sensor histidine kinase containing a LOV domain upstream from the kinase, LOVHK, which plays an important role in light-regulated Brucella virulence. In this report we study the intracellular signaling pathway initiated by the light sensor LOVHK using an integrated biochemical and genetic approach. From results of bacterial two-hybrid assays and phosphotransfer experiments we demonstrate that LOVHK functionally interacts with two response regulators: PhyR and LovR, constituting a functional two-component signal-transduction system. LOVHK contributes to the activation of the General Stress Response (GSR) system in Brucella via PhyR, while LovR is proposed to be a phosphate-sink for LOVHK, decreasing its phosphorylation state. We also show that in the absence of LOVHK the expression of the virB operon is down-regulated. In conclusion, our results suggest that LOVHK positively regulates the GSR system in vivo, and has an effect on the expression of the virB operon. The proposed regulatory network suggests a similar role for LOVHK in other microorganisms.

Highlights

Two-component systems usually consist of two proteins: a sensor domain linked to a histidine kinase (HK) domain and a RR containing the receiver and output domains [6]
In order to determine the identity of the RR functionally interacting with LOVHK, we carried out a bioinformatic analysis
Based on the fact that the REC domain determines the specificity of interaction with a HK, we cloned all REC domains from the containing genes from B. abortus into a bacterial two-hybrid vector, and screened this collection using full-length Brucella LOVHK as bait

Summary

Introduction

Brucella abortus 2308 wt, lovhk::km and ΔlovR mutant strains were grown in TSB medium at 37°C up to logarithmic phase (OD600 % 1). Wild type and the isogenic lovhk::km and ΔlovR mutant strains were grown in rich medium up to logarithmic phase and the amount of phyR expression was measured by qRT-PCR. 2013, identified a series of genes that are regulated by the GSR system in B. abortus, including rpoH1 (RNA polymerase factor sigma-32 RpoH1), dps (DNA starvation/stationary phase protection protein Dps) and lovR.

Results

Conclusion