Exploring the expression and functionality of the sRNAs in pv. tomato DC3000.

The Gac-rsm pathway is a global regulatory network that governs mayor lifestyle and metabolic changes in gamma-proteobacteria. In a previous study, we uncovered the role of CsrA proteins promoting growth and repressing motility, alginate production and virulence in the model phytopathogen pv. tomato (Pto) DC3000. Here, we focus on the expression and regulation of the regulatory sRNAs, since Pto DC3000 exceptionally has seven variants ( and ). The presented results offer further insights into the functioning of the complex Gac-rsm pathway and the interplay among its components. Overall, expressions reach maximum levels at high cell densities, are unaffected by surface detection, and require GacA for full expression. The levels of expression and GacA-dependence are determined by the sequences found in their -35/-10 promoter regions and GacA binding boxes, respectively. stands out for being the only in Pto DC3000 whose high expression does not require GacA, constituting the main component of the total pool in a mutant. The deletion of and had minor effects on Pto DC3000 motility and virulence phenotypes, indicating that can functionally replace them. On the other hand, or overexpression in a mutant did not revert its phenotype. Additionally, a negative feedback regulatory loop in which the CsrA3 protein promotes its own titration by increasing the levels of several RNAs in a GacA-dependent manner has been disclosed as part of this work.