Agrobacterium tumefaciens ferritins play an important role in full virulence through regulating iron homeostasis and oxidative stress survival

Ferritins are a large family of iron storage proteins, which are used by bacteria and other organisms to avoid iron toxicity and as a safe iron source in the cytosol.Agrobacterium tumefaciens, a phytopathogen, has two ferritin-encoding genes:atu2771andatu2477.Atu2771is annotated as a Bfr-encoding gene (Bacterioferritin, Bfr) andatu2477as a Dps-encoding gene (DNA bindingprotein fromstarved cells, Dps). Three deletion mutants (Delta bfr, Delta dps, andbfr-dpsdouble-deletion mutant Delta bdF) of these two ferritin-encoding genes were constructed to investigate the effects of ferritin deficiency on the iron homeostasis, oxidative stress resistance, and pathogenicity ofA. tumefaciens. Deficiency of two ferritins affects the growth ofA. tumefaciensunder iron starvation and excess. When supplied with moderate iron, the growth ofA. tumefaciensis not affected by the deficiency of ferritin. Deficiency of ferritin significantly reduces iron accumulation in the cells ofA. tumefaciens, but the effect of Bfr deficiency on iron accumulation is severer than Dps deficiency and the double mutant Delta bdF has the least intracellular iron content. All three ferritin-deficient mutants showed a decreased tolerance to 3 mM H(2)O(2)in comparison with the wild type. The tumour induced by each of three ferritin-deficient mutants is less than that of the wild type. Complementation reversed the effects of ferritin deficiency on the growth, iron homeostasis, oxidative stress resistance, and tumorigenicity ofA. tumefaciens. Therefore, ferritin plays an important role in the pathogenesis ofA. tumefaciensthrough regulating iron homeostasis and oxidative stress survival.