Analysis of the TIR-NB-LRR-5xPIJ Ma gene for resistance to root-knot nematodes in Prunus

Abstract:

The root-knot nematodes (RKNs) Meloidogyne spp. are persistent soil-borne plant parasites with an extremely large host range. While identifying plant susceptibility factors is an attractive strategy to develop less susceptible crops, natural resistance (R) conferred by nucleotide binding and leucine-rich repeat (NB-LRR) encoding genes are a potent control method against RKNs. The Toll Interleukin-1 Receptor (TIR) NB-LRR (TNL) encoding Ma R gene has been identified and cloned in Prunus cerasifera by the group of Daniel Esmenjaud at ISA. In plum, almond and peach, several Ma alleles/orthologs with different RKN resistance spectra have been characterized. One allele (Ma R) has been isolated from the plum accession P.2175 which provides complete and durable resistance to all RKN species tested. In addition to the strong potential of resistance that Ma confers, it presents a unique architecture with five post-LRR immunoglobulin and jelly roll-like (PIJ) domains. We undertook several approaches in order to understand better how Ma functions to activate immunity. We chose a Golden Gate cloning method together with a hairy-root in vitro RKN inoculation assay in order to establish Ma alleles functionality. In addition, we used two other genes, the model TNLs RPS4 and N, to establish the role of the PIJ domain in TNL-mediated immunity.

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