Identification of quorum sensing-regulated virulence genes in plant pathogen Pantoea ananatis.
R. SATO (1), T. Ikeda (1), T. Morohoshi (1) (1) Utsunomiya University, Japan

Pantoea ananatis is reported as a common colonist of wheat heads at ripening and causes disease symptoms in a wide range of economically important agricultural crops. Many gram-negative bacteria have a quorum-sensing system and produce N-acylhomoserine lactone (AHL) as a quorum-sensing signal molecule. Some gram-negative plant pathogens regulate their virulence by AHL-mediated quorum sensing. In previous study, we have found that plant pathogen P. ananatis SK-1 produced AHLs and cloned the AHL synthase gene eanI in the SK-1 genome. We have also demonstrated that inactivation of the chromosomal eanI gene in SK-1 caused disruption of infection of onion leaves. However, the major virulence factors regulated by quorum sensing in SK-1 are unknown. To identify the virulence genes under control of AHL-mediated quorum sensing, differential gene expression patterns among SK-1, eanI mutant, and eanI mutant with exogenous AHL, were revealed by DNA microarray. Based on the results, we selected 14 genes, which were activated by AHL-mediated quorum sensing. These selected genes were then disrupted in the chromosome of SK-1 conducted pathogenicity tests on onion leaves. As the results, leuA2 disruption mutant of SK-1 did not displayed necrotic symptoms on the onion leaf. These results demonstrated that the expression of leuA2 gene via quorum sensing involved infection of onion leaves in SK-1.

Abstract Number: P7-206
Session Type: Poster