title: The rice (Oryza sativa) blast lesion mimic mutant, blm, may confer resistance to blast pathogens by triggering multiple defense-associated signaling pathways.
abstract: Here we characterized a rice (Oryza sativa L.) blast lesion mimic (blm) mutant, identified previously in an N-methyl-N-nitrosourea-mutagenized population of the cultivar Hwacheong (wild type). The rice blm displayed spontaneous necrotic lesion formation on the leaves during development under long-day condition and temperature shift from 28 to 24 degrees C in the absence of obvious stress/disease, and provided us with a highly reproducible and convenient experimental system in the growth chamber to study blm. The blm phenotype resembled to the cell death of hypersensitive reaction (HR), and subsequent, two-dimensional gel electrophoresis (2-DGE) revealed induction of many leaf proteins; prominent among them were the three pathogenesis-related (PR) marker proteins of class 5 (one spot) and 10 (two spots). Interestingly, the rice blm manifested HR against all races tested of the rice blast fungus (Magnaporthe grisea), providing high resistance in a non-race specific manner. It was also observed that blm was highly resistant to hydrogen peroxide treatment. Using 2-DGE immunoblotting, we identified the presence of 4 new spots cross-reacting with a superoxide dismutase (SOD) antibody, only in blm, suggesting the expression of potentially new SOD protein (isoforms) during lesion formation. In the leaves of blm, autofluorescent compounds accumulated in and around the site of lesion progression. Moreover, enhanced levels of two major rice phytoalexins, sakuranetin and momilactone A were also observed in the leaves of blm. These results indicate that blm confers broad-spectrum resistance to multiple pathogens, and so, it could be hypothesized that the BLM gene product may control the HR-like cell death and its associated multiple defense signaling pathways, as evidenced by induction of known hallmark features (proteins/metabolites) linked with the defense responses, in rice.
authors.affiliation: Department of Molecular Biology, College of Natural Science, Sejong University, Seoul 143-747, South Korea.
authors.forename: Young-Ho
authors.initials: YH
authors.lastname: Jung
authors.forename: Joo-Hee
authors.initials: JH
authors.lastname: Lee
authors.forename: Ganesh Kumar
authors.initials: GK
authors.lastname: Agrawal
authors.forename: Randeep
authors.initials: R
authors.lastname: Rakwal
authors.forename: Jung-A
authors.initials: JA
authors.lastname: Kim
authors.forename: Jae-Kyung
authors.initials: JK
authors.lastname: Shim
authors.forename: Sang-Kyu
authors.initials: SK
authors.lastname: Lee
authors.forename: Jong-Seong
authors.initials: JS
authors.lastname: Jeon
authors.forename: Hee-Jong
authors.initials: HJ
authors.lastname: Koh
authors.forename: Yong-Hwan
authors.initials: YH
authors.lastname: Lee
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Iwahashi
authors.forename: Nam-Soo
authors.initials: NS
authors.lastname: Jwa
mesh_terms: D000935:Antifungal Agents / Q000378:metabolism; D004224:Diterpenes / Q000378:metabolism; D005419:Flavonoids / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D020082:Magnaporthe / Q000472:pathogenicity*; D009154:Mutation; D012275:Oryza / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology*; D018384:Oxidative Stress; D010636:Phenols / Q000378:metabolism; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D010936:Plant Extracts / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D012717:Sesquiterpenes; D015398:Signal Transduction; D013482:Superoxide Dismutase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D013729:Terpenes; D000094162:Phytoalexins
chemical_list: D000935:Antifungal Agents; D004224:Diterpenes; D005419:Flavonoids; D010636:Phenols; D010936:Plant Extracts; D010940:Plant Proteins; D012717:Sesquiterpenes; D013729:Terpenes; C099724:sakuranetin; C116023:momilactone A; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase; D000094162:Phytoalexins