Lesion mimic mutants of rice with alterations in early signaling events of defense
Article first published online: 9 OCT 2008
The Plant Journal
Volume 17, Issue 5, pages 535–545, March 1999
How to Cite
Takahashi, A., Kawasaki, T., Henmi, K., Shii, K., Kodama, O., Satoh, H. and Shimamoto, K. (1999), Lesion mimic mutants of rice with alterations in early signaling events of defense. The Plant Journal, 17: 535–545. doi: 10.1046/j.1365-313X.1999.00405.x
- Issue published online: 9 OCT 2008
- Article first published online: 9 OCT 2008
- Received 19 October 1998; revised 11 January 1999; accepted 11 January 1999.
We screened 93 lesion mimic mutants of rice for resistance to the blast fungus,Magnaporthe grisea, and found eight mutants that exhibited significant resistance to the fungus. We called these mutantscdr(cell death and resistance) and further analyzed three of them. Two mutations,cdr1andcdr2, were recessive and one,Cdr3, was dominant. Many small brownish lesions developed over the entire leaf of the mutants 20–50 days after sowing. TUNEL staining revealed that DNA fragmentation occurred in leaf blade cells of the homozygousCdr3mutants. Autofluorescence and callose deposition were visible in leaf cells of these three mutants. Activation of two defense-related genes,PBZ1andPR1, was observed in the leaves of the mutants; high expression ofPBZ1was correlated with the lesion formation in the three mutants, whereasPR1was constitutively expressed in thecdr2andCdr3mutants irrespective of the lesion formation. Levels of momilactone A, a major phytoalexin of rice, in these mutants were increased approximately 100–400-fold relative to the wild-type levels. Suspension-cultured cells of thecdr1andcdr2but notCdr3produced higher levels of H2O2 than the wild type when treated with calyculin A, an inhibitor of protein phosphatase 1. These results suggest that biochemical lesions ofcdr1andcdr2lie in the early signaling steps leading to activation of the NADPH oxidase and that type-1 protein phosphatase is operative in protein dephosphorylation involved in NADPH oxidase activation.