Flagellin from an Incompatible Strain of Pseudomonas avenae Induces a Resistance Response in Cultured Rice Cells

Abstract

The host range of <i>Pseudomonas avenae</i>is wide among monocotyledonous plants, but individual strains can infect only one or a few host species. The resistance response of rice cells to pathogens has been previously shown to be induced by a rice-incompatible strain, N1141, but not by a rice-compatible strain, H8301. To clarify the molecular mechanism of the host specificity in<i>P. avenae</i>, a strain-specific antibody that was raised against N1141 cells and then absorbed with H8301 cells was prepared. When a cell extract of strain N1141 was separated by SDS-polyacrylamide gel electrophoresis and immunostained with the N1141 strain-specific antibody, only a flagellin protein was detected. Purified N1141 flagellin induced the hypersensitive cell death in cultured rice cells within 6 h of treatment, whereas the H8301 flagellin did not. The hypersensitive cell death could be blocked by pretreatment with anti-N1141 flagellin antibody. Furthermore, a flagellin-deficient N1141 strain lost not only the induction ability of hypersensitive cell death but also the expression ability of the <i>EL2</i> gene, which is thought to be one of the defense-related genes. These results demonstrated that the resistance response in cultured rice cells is induced by the flagellin existing in the incompatible strain of<i>P. avenae</i> but not in the flagellin of the compatible strain.