Mutation in clpxoo4158Reduces Virulence and Resistance to Oxidative Stress in Xanthomonas oryzae pv. oryzae KACC10859

Abstract

Cyclic AMP receptor-like protein (Clp), is known to be a global transcriptional regulator for the expression of virulence factors in Xanthomonas campestris pv. campestris (Xcc). Sequence analysis showed that Xanthomonas oryzae pv. oryzae (Xoo) contains a gene that is strongly homologous to the Xcc clp. In order to determine the role of the Clp homolog in Xoo, a marker exchange mutant of <TEX>$clp_{xoo4158}$</TEX> was generated. Virulence and virulence factors, such as the production of cellulase, xylanase, and extracellular polysaccharides (EPS) and swarming motility were significantly decreased in the <TEX>$clp_{xoo4158}$</TEX> mutant. Moreover, the mutation caused the strain to be more sensitive to hydrogen peroxide and to over-produce siderophores. Complementation of the mutant restored the mutation-related phenotypes. Expression of <TEX>$clp_{xoo4158}$</TEX>, assessed by reverse-transcription realtime PCR and clp promoter activity, was significantly reduced in the rpfB, rpfF, rpfC, and rpfG mutants. These results suggest that the clp homolog, <TEX>$clp_{xoo4158}$</TEX>, is involved in the control of virulence and resistance against oxidative stress, and that expression of the gene is controlled by RpfC and RpfG through a diffusible signal factor (DSF) signal in Xanthomonas oryzae pv. oryzae KACC10859.