R genes: Structure, recognition, signaling, & evolution – part 1 Major classes of R genes R gene structure Early signaling events R gene evolution

The zigzag model for plant pathogen interactions Dangl and Jones Nature 444:

Plant immune system Dangl Science. 341:746

R protein structure R proteins encompass multiple domains involved in different aspects of activation and signaling, and intramolecular interaction is involved. Domains TIR – Toll/Interleukin-1 receptor CC – Coiled coil NBS – Nucleotide binding site LRR – Leucine-rich repeat R protein classes TIR-NBS-LRR, TNL CC-NBS-LRR, CNL NB-LRR, NBS-LRR, NLR – Nucleotide-binding leucine-rich repeat

Liu et al J. Genet. Genom. 34: Cloned disease resistance genes NBS-LRR is largest class Major subclasses of NBS-LRR are: - CC-NBS-LRR - TIR-NBS-LRR R gene class and pathogen are not correlated TIR-NBS-LRR are not found in cereals

Liu et al J. Genet. Genom. 34: Major classes of R proteins

Tammeling et al. (2002) Plant Cell 14, 2929–2939 I-2 Mi-1 Nucleotide binding site (NBS) P loop sequences kinase 24 hydrophobic amino acids followed by D (e.g. LIVLD ) kinase 3aHighly conserved tyrosine or arginine (e.g. FGNGSR) GLPL MHDV

Inferred structure of R protein nucleotide binding sites McHale et al Genome Biology. 7:212

Inferred structure of LRR domain McHale et al Genome Biology. 7:212

Variation in numbers of LRRs

Structural models of domains in NLR proteins Takken Curr. Opin. Plant Biol. 15:

Model of LRR motif of lettuce downy mildew resistance protein, Dm3 Michelmore Annu. Rev. Phytopathol. 51:

Michelmore and Meyers Genome Res. 8: LRR is least conserved part of R genes

NLR proteins are involved in plant & animal innate immunity Bonardi et al. (2012) Curr. Opin. Immunol. 24:41-50

Evidence for intramolecular interaction between domains of a CNL protein Moffett et al. (2002) EMBO J. 21:4511 CP-independent HR when TEX’d Co-expression of full-length GPA2 with either LRR or ARC−LRR of Rx did not lead to a CP-dependent HR. However, co-expression of GPA2 with Rx NBS−LRR resulted in a CP-dependent HR (Figure 2B). This result demonstrates that a CC domain can be provided by full-length CC−NBS−LRR protein. Our observation that Rx NBS−LRR produced a CP-dependent HR when expressed in rx genotype potato leaves can be explained in the same way (Figure 2C). Presumably, a CC domain was provided to NBS−LRR by full-length homologues of Rx and GPA2 that are present in the rx potato genome (Bendahmane et al., 1999).

Intramolecular interactions - continued

Mestre Plant Cell. 18: N protein oligomerizes in response to elicitor

NLR proteins – Mechanisms for activation Bonardi et al. (2012) Curr. Opin. Immunol. 24:41-50

NLR folding and signaling Takken Curr. Opin. Plant Biol. 15:

Ting et al Nat. Rev. Immunol. 8: Signaling by animal NLR proteins