The Root Knot Nematode Resistance Gene Mi from Tomato Is a Member of the Leucine Zipper, Nucleotide Binding, Leucine-Rich Repeat Family of Plant Genes

Abstract

The Mi locus of tomato confers resistance to root knot nematodes. Tomato DNA spanning the locus was isolated as bacterial artificial chromosome clones, and 52 kb of contiguous DNA was sequenced. Three open reading frames were identified with similarity to cloned plant disease resistance genes. Two of them, Mi-1.1 and Mi-1.2, appear to be intact genes; the third is a pseudogene. A 4-kb mRNA hybridizing with these genes is present in tomato roots. Complementation studies using cloned copies of Mi-1.1 and Mi-1.2 indicated that Mi-1.2, but not Mi-1.1, is sufficient to confer resistance to a susceptible tomato line with the progeny of transformants segregating for resistance. The cloned gene most similar to Mi-1.2 is Prf, a tomato gene required for resistance to Pseudomonas syringae. Prf and Mi-1.2 share several structural motifs, including a nucleotide binding site and a leucine-rich repeat region, that are characteristic of a family of plant proteins, including several that are required for resistance against viruses, bacteria, fungi, and now, nematodes.

Transcriptomics of induced defense responses to greenbug aphid feeding in near isogenic wheat lines

“…Since most phloem-feeders cause minimal physical damage to the plant tissue, the resulting defense responses are similar to those associated with PAMP or MAMP and are recognized by pattern recognition receptors (PRRs) present on the surface of plant cells [3,8]. Perception of phloem-feeding herbivores by R genes similar to disease resistance R proteins encodes a coiled coil nucleotide-binding leucine rich repeat (CC-NBS-LRR) protein [11][12][13][14]. Perception of feeding behavior by plants with R gene was shown to activate phytohormone, salicylic acid (SA)-dependent signaling cascade and callose deposition [14].…”

Allele mining in Solanum: conserved homologues of Rpi-blb1 are identified in Solanum stoloniferum

“…Rpi-blb2 resides in a locus harbouring at least 15 Mi gene homologues on chromosome VI, and the Rpi-blb2 protein shows 82% sequence identity to the Mi-1 protein . Mi-1 is a gene of tomato that confers resistance to the root knot nematode Meloidogyne incognita (Milligan et al 1998).…”

Genetic mapping and transcription analyses of resistance gene loci in potato using NBS profiling

“…The fact that a single R gene can interfere with pathogens that aVect diVerent tissues, as is demonstrated for the Mi resistance gene, which in tomato confers resistance to three species of root knot nematodes (Meloidogyne spp.) as well as to the potato aphid Macrosiphum euphorbiae (Vos et al 1998;Rossi et al 1998;Milligan et al 1998) and to both B-and Q-biotypes of whiteXy Bemisia tabaci (Nombela et al 2003), suggests that R genes are transcribed in multiple tissues.…”