Ankyrin-Like Protein AnkB Interacts with CatB, Affects Catalase Activity, and Enhances Resistance of Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae pv. oryzicola to Phenazine-1-Carboxylic Acid

Xanthomonas oryzae pv. oryzae, which causes rice bacterial leaf blight, andXanthomonas oryzae pv. oryzicola, which causes rice bacterial leaf streak, are important plant-pathogenic bacteria. A member of the adaptor protein family, ankyrin protein, has been investigated largely in humans but rarely in plant-pathogenic bacteria. In this study, a novel ankyrin-like protein, AnkB, was identified inX. oryzae pv. oryzae andX. oryzae pv. oryzicola. The expression ofankB was significantly upregulated when these bacteria were treated with phenazine-1-carboxylic acid (PCA).ankB is located 58 bp downstream of the genecatB (which encodes a catalase) in both bacteria, and the gene expression ofcatB and catalase activity were reduced followingankB deletion inX. oryzae pv. oryzae andX. oryzae pv. oryzicola. Furthermore, we demonstrated that AnkB directly interacts with CatB by glutathioneS -transferase (GST) pulldown assays. Deletion ofankB increased the sensitivity ofX. oryzae pv. oryzae andX. oryzae pv. oryzicola to H2 O2 and PCA, decreased bacterial biofilm formation, swimming ability, and exopolysaccharide (EPS) production, and also reduced virulence on rice. Together our results indicate that the ankyrin-like protein AnkB has important and conserved roles in antioxidant systems and pathogenicity inX. oryzae pv. oryzae andX. oryzae pv. oryzicola.IMPORTANCE This study demonstrates that the ankyrin protein AnkB directly interacts with catalase CatB inXanthomonas oryzae pv. oryzae andXanthomonas oryzae pv. oryzicola. Ankyrin protein AnkB can affect the gene expression ofcatB , catalase activity, and sensitivity to H2 O2 . InXanthomonas spp., the locations of genesankB andcatB and the amino acid sequence of AnkB are highly conserved. It is suggested that in prokaryotes, AnkB plays a conserved role in the defense against oxidative stress.