Regulation of angR, a gene with regulatory and biosynthetic functions in the pJM1 plasmid-mediated iron uptake system of Vibrio anguillarum.

AngR and the product(s) encoded in the trans-acting factor (TAF) region are necessary for the full expression of the pJM1 plasmid-mediated anguibactin iron-uptake system in Vibrio anguillarum (Va). In this report, we analyzed the factors that affect the expression of the angR gene. Northern blot analysis showed that angR encodes a 3.1-kb transcript which is expressed only under iron-limiting conditions. Measurement of steady-state RNA levels show that, under iron-limiting conditions, angR is positively regulated at the transcriptional level by product(s) of the Va TAF region. However, this enhancement of angR expression by TAF does not occur at high levels of the AngR protein, as assessed by using an angR::lacZ fusion in the presence of a construct containing angR under the control of ptac. We also report that repression of angR by iron could possibly be mediated by an endogenous Va antisense RNA beta, which contains a stem-loop structure complementary to the stem-loop structure located at the 5' end of angR.