1Department of Entomology, University of Arkansas, 320 Agriculture Building, Fayetteville 72701; 2DNA Plant Technologies, 6701 San Pablo Ave., Oakland, CA, 94608; 3Department of Nematology, University of California, 1 Shields Ave., Davis 95616; 4Department of Entomology, University of California, 1 Shields Ave., Davis 95616, U.S.A.
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Accepted 25 November 2003.
Mi-1.2, a member of the intracellular, nucleotide-binding site-leucine-rich repeat family of resistance genes, confers resistance in tomato (Lycopersicon esculentum) against both root-feeding nematodes and leaf-feeding aphids. Nematode resistance is effective in all life stages of the plant; in contrast, Mi-mediated aphid resistance is developmentally regulated, and protects mature plants but not seedlings against aphid infestation. To determine if the onset of aphid resistance is regulated by Mi-1.2 transcript abundance, we compared aphid resistance and Mi-1.2 transcript levels in seedlings and flowering plants. Paired bioassays and RNase protection assays revealed that Mi-1.2 is transcribed in the leaves prior to the onset of aphid resistance, and that transcript levels are comparable in seedlings and flowering life stages. Furthermore, constitutive overexpression of Mi-1.2 in transgenic plants did not hasten the onset of aphid resistance in seedlings, or boost the level of resistance observed in flowering plants. These data demonstrate that Mi-1.2 transcript levels do not modulate the degree of aphid resistance in tomato leaves, or control the differences in regulation between aphid and nematode resistance.
© 2004 The American Phytopathological Society