2012 Dodds and Rathjen 2010 Hogenhout et al. In plants, NLR proteins recognize effectors: pathogen-secreted molecules that normally modulate host cell processes to the benefit of the pathogen ( Bozkurt et al. The largest family of intracellular immune receptors is the nucleotide-binding (NB) leucine-rich repeat (LRR) (or NLR) protein family, an important element of defense against pathogens in both plants and animals ( Jacob et al. Plants resist pathogenic invasion through cell surface and intracellular immune receptors that recognize pathogen-secreted molecules and activate immune responses ( Dodds and Rathjen 2010 Win et al. Engineering synthetic wide-spectrum immune receptors that target more than one pathogen is one approach to rapidly deliver agronomically useful resistance genes. The challenge for plant breeders and biotechnologists is to generate new resistance gene specificities rapidly enough to keep up with pathogen evolution. However, pathogens continuously evolve new races that overcome immunoreceptor-specific mediated disease resistance. Moreover, in Arabidopsis, RPS4 and RRS1 mediate resistance to the bacteria Pseudomonas syringae and Ralstonia solanacearum but also to the fungus Colletotrichum higginsianum ( Birker et al. Cf-2, an extracellular tomato immune receptor, also mediates resistance to both the fungus Cladosporium fulvum and the root-parasitic nematode Globodera rostochiensis ( Lozano-Torres et al. One example is the tomato gene Mi-1.2, which confers resistance to pathogens from different phyla: arthropods (aphids and whiteflies) and a nematode ( Atamian et al. Although this can be achieved by pyramiding multiple immune receptors with different pathogen resistance spectra, single R genes that function against multiple pathogens do occur. One challenge is to engineer plants with broad-spectrum disease resistance (i.e., that can defend against a wide spectrum of pathogens). Sustainable crop improvement based on these mechanisms often involve resistance ( R) genes: plant loci that encode immune receptors ( Cook 2000 Jones et al. Plants have evolved various disease resistance mechanisms to defend against pathogens. Plant diseases are one of the main threats to modern human life, and the need for sustainable crop disease resistance is becoming increasingly urgent ( Fisher et al. Our results suggest that synthetic immune receptors can be engineered to confer resistance to phylogenetically divergent pathogens and indicate that knowledge gathered for one NLR could be exploited to improve NLR from other plant species. lycopersici effectors compared with the wild-type I2 protein. Further, I2 I141N has an expanded response spectrum to F. Remarkably, I2 I141N conferred partial resistance to P. One mutant in the N-terminal coiled-coil domain, I2 I141N, appeared sensitized and displayed markedly increased response to AVR3a. We discovered that wild-type I2 protein responds weakly to AVR3a. We transferred previously identified R3a mutations to I2 to assess the degree to which the resulting I2 mutants have an altered response. lycopersici, is the tomato ortholog of R3a. I2, another NLR that mediates resistance to the wilt-causing fungus Fusarium oxysporum f. We previously reported single-residue mutations that expand the response of the potato immune receptor R3a to AVR3a EM, a stealthy effector from the late blight oomycete pathogen Phytophthora infestans. How NLR receptors respond to pathogens is inadequately understood.

Plants and animals rely on immune receptors, known as nucleotide-binding domain and leucine-rich repeat (NLR)-containing proteins, to defend against invading pathogens and activate immune responses.

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