Fig 1. Pos19 is induced by singlet oxygen and peroxides.
(A) Graphical representation of the Pos19 locus in R. sphaeroides wild-type strain 2.4.1. The pos19 gene is located on chromosome 2 between cxp and fadB. The conserved RpoE-dependent promoter (PRpoE) and the Rho-independent terminator (lollipop structure) are indicated. (B) Northern blot for stress-dependent Pos19 induction. R. sphaeroides wild-type 2.4.1 cultures were treated with stress-generating chemicals and samples collected at time points 0 and 7 min. Singlet oxygen (1O2) was generated by the addition of 0.2 μM methylene blue in the presence of high light intensities (800 W m-2). Hydrogen peroxide (H2O2) and tert-butyl hydroperoxide (tBOOH) were added in final concentrations of 1 mM and 300 μM, respectively. 250 μM of paraquat (PQ) were used for the generation of superoxide radicals (O2‒). 5S rRNA was probed as loading control. (C) Northern blot for RpoE-dependent Pos19 expression. The R. sphaeroides wild-type (wt), the Pos19 over-expression (pPos19), RpoHI and RpoHII mutant strains, as well as a strain lacking the rpoE-chrR locus (TF18), were treated with the indicated stress-generating chemicals as described above. Samples were collected at the indicated time points. 5S rRNA was probed as loading control.