, 2003). Ftn and Bfr function similarly as iron-storage proteins, preserving iron in a nonreactive form that can be released and used

as a nutrient source during conditions of iron starvation (Abdul-Tehrani et al., 1999; Chen et al., 2010). Dps proteins are involved in iron detoxification. Dps proteins protect DNA from the harmful Fenton reaction by catalysing the oxidation of two ferrous iron molecules for every one hydrogen peroxide (H2O2) molecule and thus prevent the production of toxic hydroxyl radicals (Zhao et al., 2002; Ceci et al., 2003). The erythrin-vacuolar iron transport (Er-VIT1) GSK-3 cancer protein, a member of the Ferritin-like superfamily, has a distinct structure consisting of two major domains (Fig. 1) (Andrews, 2010). First, the N-terminal Er or Ferritin-like domain contains the four-helical bundle and conserved amino acid residues for a di-iron site. Second, the C-terminal domain is a membrane-embedded VIT1 domain that is homologous to Arabidopsis VIT1, which is involved in iron transport into vacuoles (Kim et al., 2006). Arabidopsis VIT1 has a 62% Volasertib in vitro amino acid similar to the yeast Ca2+-sensitive cross-complementer 1 (CCC1) protein. CCC1 is an iron/manganese transporter that transfers iron from the cytoplasm to vacuoles (Li et al., 2001). At present, the Er-VIT1 protein has not been characterized, and thus, the protein’s function

is still not known. The A. tumefaciens mbfA gene (Atu0251), a member of Er-VIT1 family, encodes a putative membrane-bound ferritin (MbfA) that is predicted

to be regulated by the iron response regulator (irr) (Rodionov et al., 2006). In closely related Rhizobium leguminosarum and Bradyrhizobium japonicum bacteria, it has been demonstrated that transcription of mbfA is regulated by Irr in response to iron (Rudolph et al., 2006; Todd et al., 2006). Agrobacterium tumefaciens Irr co-modulates iron homeostasis with the rhizobial iron regulator (RirA), in which Irr plays a contrasting role in positively controlling iron uptake and transport genes (Hibbing & Fuqua, 2011). However, the regulation and physiological function of A. tumefaciens mbfA have not been studied. Here, an A. tumefaciens mbfA mutant strain was generated to investigate the physiological functions of Sclareol mbfA in response to iron and H2O2 stresses. Agrobacterium tumefaciens strains used in this study include the wild-type strain (NTL4), a Ti plasmid-cured derivative of strain C58 (Luo et al., 2001), a catalase-deficient strain (KC05, katA and catE double mutation) (Prapagdee et al., 2004) and a rhizobial iron regulator mutant strain (PN094, previously named NTLrirA) (Ngok-ngam et al., 2009). Agrobacterium tumefaciens strains were grown aerobically at 28 °C in Luria–Bertani (LB) medium or on LB plates containing 1.5% agar (LA), supplemented with 100 μg mL−1 carbenicillin (Cb), 25 μg mL−1 chloramphenicol (Cm), 90 μg mL−1 gentamicin (Gm) or 30 μg mL−1 kanamycin (Km), as required. Escherichia coli strains BW20767 (Metcalf et al.