Ferritin Bfr of Xanthomonas oryzae pv. oryzicola : A ferric‑specific iron storage protein essential for pathogenicity and a promising candidate target for disease control

Iron is essential but toxic in excess, forcing bacterial pathogens to balance iron acquisition against oxidative damage. Here, we show that the bacterioferritin (Bfr) in Xanthomonas oryzae pv. oryzicola (Xoc) contributes to iron homeostasis, metabolic adaptation, and redox balance, thereby influencing virulence. The Δbfr mutant accumulated intracellular Fe2⁺, displayed altered cell morphology, and showed reduced biofilm formation, whereas swimming motility remained unchanged. Activities of the antioxidant enzymes SOD and CAT increased, yet levels of malondialdehyde (MDA) did not change. The mutant displayed altered protein acetylation and lost the ability to adjust its growth when iron levels changed. On rice plants, the Δbfr mutant caused greatly reduced disease symptoms, and it also showed a weaker hypersensitive response on tobacco. Collectively, these results identify Bfr as a ferric-specific iron storage protein that functions as an iron-homeostasis regulator and is essential for Xoc pathogenicity. Given its crucial role in virulence, Bfr represents a promising candidate target for the development of antibacterial agents to control bacterial leaf streak of rice.