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Rme1 is Necessary for Mi-1-Mediated Resistance and Acts Early in the Resistance Pathway

January 2004 , Volume 17 , Number  1
Pages  55 - 61

Oscar Martinez de Ilarduya , 1 Gloria Nombela , 2 Chin-Feng Hwang , 3 Valerie M. Williamson , 3 Mariano Muñiz , 2 and Isgouhi Kaloshian 1

1Department of Nematology, University of California, Riverside, CA 92521, U.S.A.; 2Departamento de Protección Vegetal, Centro de Ciencias Medioambientales, CSIC, Serrano 115 Dpdo. 28006 Madrid, Spain; 3Department of Nematology, University of California, Davis, CA 92506, U.S.A.

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Accepted 9 September 2003.

The tomato gene Mi-1 confers resistance to root-knot nematodes (Meloidogyne spp.), potato aphid, and whitefly. Using genetic screens, we have isolated a mutant, rme1 (resistance to Meloidogyne spp.), compromised in resistance to M. javanica and potato aphid. Here, we show that the rme1 mutant is also compromised in resistance to M. incognita, M. arenaria, and whitefly. In addition, using an Agrobacterium-mediated transient assay in leaves to express constitutive gain-of-function mutant Pto L205D, we demonstrated that the rme1 mutation is not compromised in Pto-mediated hypersensitive response. Moreover, the mutation in rme1 does not result in increased virulence of pathogenic Pseudomonas syringae or Mi-1-virulent M. incognita. Using a chimeric Mi-1 construct, Mi-DS4, which confers constitutive cell death phenotype and A. rhizogenes root transformation, we showed that the Mi-1-mediated cell death pathway is intact in this mutant. Our results indicate that Rme1 is required for Mi-1-mediated resistance and acts either at the same step in the signal transduction pathway as Mi-1 or upstream of Mi-1.

© 2004 The American Phytopathological Society