Does SwrA affect DegU-mediated transcriptional activation of aprE?

Bacillus subtilis subtilisin E (AprE) is one of main industrial proteases. Expression of aprE is regulated by a complex network of activators and repressors that comprises AbrB, SinR, ScoC, CodY and DegU. The latter is a global regulator activated via phosphorylation mediated by its cognate sensor kinase DegS. It has been shown that DegU~P can physically interact with SwrA, a small protein essential for swarming motility. The cooperative effect of DegU~P and SwrA has been demonstrated on two promoters: PA(fla/che), which codes for the major structural components of the flagellum; and Ppgs, that encodes the genes for γ-PGA biosynthesis. On those promoters, SwrA appears to act as a modulator of DegU activity, promoting transcriptional activation. To date, no studies addressed the role of SwrA on the regulation exerted by DegU~P on PaprE. The aim of this work is to investigate whether SwrA is involved in modifying DegU activity also at the subtilisin promoter. To this end, the construct containing a GFP reporter gene under the control of PaprE, kindly provided by Jan-Willem Veening, was used to carry out quantitative and qualitative analyses of aprE expression. The construct was inserted in isogenic Bacillus strains, differing for the status of both the swrA allele (swrA+, swrA- and ΔswrA) and the degUS TCS (degUSwt, degU32Hy, degS200Hy). The PaprE transcriptional profile will be presented together with fluorescent microscopy data.