Transcriptional Regulation of thephoPROperon inBacillus subtilis

Abstract

When Bacillus subtilis is subjected to phosphate starvation, the Pho regulon is activated by the PhoP-PhoR two-component signal transduction system to elicit specific responses to this nutrient limitation. The response regulator, PhoP, and its cognate histidine sensor kinase, PhoR, are encoded by the phoPR operon that is transcribed as a 2.7-kb bicistronic mRNA. The phoPR operon is transcribed from two A -dependent promoters, P 1 and P 2 . Under conditions where the Pho regulon was not induced (i.e., phosphate-replete conditions or phoR-null mutant), a low level of phoPR transcription was detected only from promoter P 1 . During phosphate starvation-induced transition from exponential to stationary phase, the expression of the phoPR operon was up-regulated in a phosphorylated PhoP (PhoPϳP)-dependent manner; in addition to P 1 , the P 2 promoter becomes active. In vitro gel shift assays and DNase I footprinting experiments showed that both PhoP and PhoPϳP could bind to the control region of the phoPR operon. The data indicate that while low-level constitutive expression of phoPR is required under phosphate-replete conditions for signal perception and transduction, autoinduction is required to provide sufficient PhoPϳP to induce other members of the Pho regulon. The extent to which promoters P 1 and P 2 are activated appears to be influenced by the presence of other sigma factors, possibly the result of sigma factor competition. For example, phoPR is hyperinduced in a sigB mutant and, later in stationary phase, in sigH, sigF, and sigE mutants. The data point to a complex regulatory network in which other stress responses and post-exponential-phase processes influence the expression of phoPR and, thereby, the magnitude of the Pho regulon response.

Domain Structure of Virulence-associated Response Regulator PhoP of Mycobacterium tuberculosis

“…1B). Also, members like PhoP from Salmonella enterica and B. subtilis form dimers in solution and bind DNA regardless of its phosphorylation status (33,34). However, phosphorylation of PhoB from E. coli induces dimerization and increases its affinity for the target DNA (35).…”

Unraveling the Secret Lives of Bacteria: Use of In Vivo Expression Technology and Differential Fluorescence Induction Promoter Traps as Tools for Exploring Niche-Specific Gene Expression

“…For example, virulence factors of animal pathogens have been identified by analyzing bacterial responses to changes in temperature (166,178), iron concentration (146,182), pH (189), exposure to oxidative stress (282), and phosphate starvation (211). Similarly, the biology of rhizosphere-colonizing bacteria has been studied using simplified in vitro approaches.…”

New insights into the regulatory networks of paralogous genes in bacteria

“…In the first case, s F forms a feed-forward motif with the anti-anti-sigma factor SpoIIAA and the anti-sigma factor SpoIIAB, as s F regulates the expression of SpoIIAA and SpoIIAB, whereas SpoIIAA modulates the expression of SpoIIAB. In a similar manner, the second feed-forward loop is formed by s E , PhoP and PhoR, which are involved in phosphate uptake, postexponential growth phase and other stress responses (Pragai et al, 2004). Duplication events, or mutations in the duplicated regulatory genes or in the regulatory target sites, can generate new feed-forward motifs useful for the rewiring of the regulatory networks of the paralogous genes, which favours the adaptation process of the organism as it responds to niche adaptation (Gelfand, 2006).…”