Pseudogenization of the cntQ permease confers distinct yersinopine-metal uptake selectivity in Yersinia species

Yersinopine is a nicotianamine-like metallophore recently inferred from a biochemical study, however its production in vivo and functional role have not been evaluated. Intriguingly, the Yersinia pestis cnt operon (cntPQRLMI) encoding yersinopine biosynthesis and transport (with cntPQR encoding a predicted ABC transport system, cntLM the two biosynthetic enzymes and cntI the predicted yersinopine exporter) shows two frameshift mutations in the cntQ gene encoding the permease, whereas this gene appears intact in Yersinia pseudotuberculosis. This pseudogenization, which occurred during the emergence of Y. pestis from Y. pseudotuberculosis, questions the role of yersinopine (if any) in both species. Here we show that yersinopine is secreted by both Y. pestis and Y. pseudotuberculosis in metal scarce conditions, and expression of the operon is repressed by the zinc uptake regulator (Zur). Surprisingly, the cnt operon was found to be involved in iron uptake in Y. pseudotuberculosis whereas it played a role in zinc acquisition in Y. pestis. Furthermore, mutation of cntQ in Y. pseudotuberculosis triggered a switch from iron import to zinc import, therefore recapitulating the phenotype observed in Y. pestis. This work demonstrates the production of yersinopine in two closely related bacteria in zinc scarce conditions, and highlights the effect of a pseudogenization event triggering a global change in metal uptake specificity. IMPORTANCEYersinia pestis, the bacteria responsible for plague, emerged from Yersinia pseudotuberculosis less than 6.000 years ago. Genetically close, only a few acquisition and loss of genes played a crucial role in the emergence of flea-borne plague. In this context, the cnt operon encoding the yersinopine metallophore biosynthesis, export and recovery of the metal-yersinopine complexes appears complete in Y. pseudotuberculosis. In contrast, a frameshift mutation impairs the permease CntQ in Y. pestis. This questions whether these species can produce and use yersinopine and, if so, what would be the impact on their metal uptake. Here, we report the production of the metallophore yersinopine in both bacteria, though it is used for iron uptake in Y. pseudotuberculosis whereas it is important for zinc uptake in Y. pestis. By introducing a frameshift mutation in the cntQ gene of Y. pseudotuberculosis, we observed a shift toward zinc uptake, recapitulating an event that happened during the emergence of Y. pestis from its ancestor.