The Roles of Two Genes in the Virulence and Stress Resistance of .

The Hfq protein is a global small RNA chaperone that interacts with regulatory bacterial small RNAs (sRNA) and plays a role in the post-transcriptional regulation of gene expression. The roles of Hfq in the virulence and pathogenicity of several infectious bacteria have been reported. This study was conducted to elucidate the functions of two genes in , a causal agent of rice grain rot. Therefore, mutant strains of the rice-pathogenic BGR1, targeting each of the two genes, as well as the double defective mutant were constructed and tested for several phenotypic characteristics. Bacterial swarming motility, toxoflavin production, virulence in rice, siderophore production, sensitivity to HO, and lipase production assays were conducted to compare the mutant strains with the wild-type BGR1 and complementation strains. The 1 gene showed more influence on bacterial motility and toxoflavin production than the 2 gene. Both genes were involved in the full virulence of in rice plants. Other biochemical characteristics such as siderophore production and sensitivity to HO induced oxidative stress were also found to be regulated by the 1 gene. However, lipase activity was shown to be unassociated with both tested genes. To the best of our knowledge, this is the first study to elucidate the functions of two genes in . Identification of virulence-related factors in will facilitate the development of efficient control measures.