Noriko Tanaka

Flagellin from an incompatible strain of Pseudomonas avenae induces a resistance response in cultured rice cells.

The host range of Pseudomonas avenaeis 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 inP. avenae, 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 EL2 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 ofP. avenae but not in the flagellin of the compatible strain.

Flagellin from an Incompatible Strain of Acidovorax avenae Mediates H2O2 Generation Accompanying Hypersensitive Cell Death and Expression of PAL, Cht-1, and PBZ1, but Not of LOX in Rice

Acidovorax avenae causes a brown stripe disease in monocot plants. We recently reported that a rice-incompatible strain of A. avenae caused hypersensitive cell death in rice and that the flagellin of the incompatible strain was involved in this response. The incompatible strain induced the rapid generation of H2O2 accompanying hypersensitive cell death and the expression of defense genes such as PAL, Cht-1, PBZ1, and LOX, whereas the compatible strain did not. The purified incompatible flagellin also induced the expression of PAL, Cht-1, and PBZ1, but LOX expression was not induced by the incompatible flagellin. PAL and LOX enzymatic activities were increased by inoculation with the incompatible strain, whereas only PAL activity was increased by the incompatible flagellin. Interestingly, the flagellin-deficient incompatible strain lost the ability to generate H2O2 and induce hypersensitive cell death, but PAL, Cht-1, and PBZ1 expression still were induced by inoculation with the deficient strain, suggesting that induction of these genes is regulated not only by flagellin but also by some other signal. Thus, the incompatible flagellin of A. avenae is a specific elicitor in rice, but it is not the only factor capable of inducing the rice defense system.

Rice cDNA Microarray-Based Gene Expression Profiling of the Response to Flagellin Perception in Cultured Rice Cells

Incompatible strains of Acidovorax avenae elicit an immune response in cultured rice cells, with immunity specifically induced by the flagellin of the incompatible strain. To identify genes regulated by flagellin perception signaling in cultured rice cells, gene expression patterns were analyzed with rice cDNA microarrays, including 3,353 independent rice cDNA clones. In all, 131 genes were differentially expressed between incompatible and compatible interactions. K-means clustering showed that 94 genes were upregulated and 32 genes were downregulated during incompatible interactions, whereas only 5 genes were upregulated during compatible interactions. Among the 126 genes that were up- or downregulated during incompatible interactions, expression of 46 genes was decreased when cultured rice cells were inoculated with a flagellin-deficient incompatible strain (delta fla1141-2), indicating that approximately 37% of the 126 genes were directly controlled by flagellin perception. Real-time reverse-transcription polymerase chain reaction analysis using flagellins purified from incompatible or compatible strains was performed to confirm flagellin-regulated expression of candidate genes selected by microarray analysis. Results showed that induction of some genes involved in the immune response is regulated not only by the flagellin perception pathway, but also by another recognition molecule-perception pathway.

The kinematic characteristics of a big toe and a new input device -Toe Mouse-

A new hands free mouse cursor position control device “Toe Mouse” was developed. The mouse is controlled by a toe with three dimensional pressure sensor unit and the user could handle keyboard and other devices with both hands during a PC operation.