LAUSR

The plant bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight of rice, which is one of the most destructive diseases prevalent in Asia and parts of Africa. Despite many years of research, how Xoo causes bacterial blight of rice is still not completely understood. Here, we show that the loss of the rocF gene caused significant decrease in the virulence of Xoo in the susceptible rice cultivar IR24. Bioinformatics analysis demonstrated that the rocF gene encodes an arginase. Quantitative real-time PCR (qRT-PCR) and Western blot assays revealed that expression of the rocF gene was significantly induced by rice and arginine. The rocF gene deletion mutant strain showed elevated sensitivity to hydrogen peroxide (H2O2), reduced production of extracellular polysaccharide (EPS) and reduced biofilm formation, all of which are important determinants for the full virulence of Xoo, compared to those of the wild-type strain. Taken together, the results of this study revealed a mechanism by which a bacterial arginase is required for the full virulence of Xoo on rice because of its contribution to tolerance to reactive oxygen species, production of EPS, and biofilm formation.