Expression Of HrmA Gene Enhance Disease Resistance Rice Plants

HrmA, an avirulence-like gene was isolated from Pseudomonas syringae pv. syrongae, conferring broad-spectrum avirulence on P. s.syringae in all examined suspectible host tobacco. Futhermore, induced disease resistance is observed on rice by treatment with P. s.syringae. In this study, I investigated the disease resistance on the hrmA transgenic rice plants.There were 35 transgenic lines generated from the hrmA gene transformation. However, these transgenic plants could be divided into three groups:(l) plants without tassels or die in the field (nine lines), (2) plants with few tassels but no seeds (eight lines), (3) plants with normal seeds (eighteen lines). 11 lines from group(3) were used in this study. PCR analysis indicated that there were 8 positive lines of the 11 lines. The expression level of hrmA gene in the transgenic plants must be low to some degree. hrmA mRNA could not be detected in the eight lines plants by Northern blot analysis and could only be detected by RT-PCR analysis.Then, Resistance of the transgenic plants to Magnaporthe grisea was tested by inoculated the plants with M.grisea 97-220E3 and 1528. The hrmA transgenic plants exhibited more resistance to M.grisea comparing with the non-transgenic plants. The expression level of pathogen-related PAL, pBZl and Glue genes were enhanced in the transgenic plants by Northern blot and RT-PCR analysis . These results suggest that the enhanced resistance against M.grisea in the hrmA gene transgenic plants might correlate with the enhanced expression of pathogen-related genes.Last, a simple array containing 89 DNA fragments of OsWRKY genes and 43 DNA fragments of pathogen-related genes(PRs) prepared by Dr. Wu Kun-lu in our lab was used to analyze whether the genes of the WRKY transcript factor superfamily participate the enhance disease resistance of the transgenic plants by hrmA gene. The results showed that 21 WRKY genes and 15 PRs changed remarkably in the line s49 transgenic plants. Results by Northern blot and RT-PCR analysis of some genes also indicated that some WRKY genes participate in the enhance disease resistance, and the resistance are related to the expression level of hrmA gene in the transgenic plants.