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Molecular determinants of resistance activation and suppression by Phytophthora infestans effector IPI-O - PubMed

Molecular determinants of resistance activation and suppression by Phytophthora infestans effector IPI-O

Yu Chen et al. PLoS Pathog. 2012.

Erratum in

  • PLoS Pathog. 2012 Sep;8(9). doi:10.1371/annotation/75775518-f06e-4148-a639-31cfc6972b2e

Abstract

Despite intensive breeding efforts, potato late blight, caused by the oomycete pathogen Phytophthora infestans, remains a threat to potato production worldwide because newly evolved pathogen strains have consistently overcome major resistance genes. The potato RB gene, derived from the wild species Solanum bulbocastanum, confers resistance to most P. infestans strains through recognition of members of the pathogen effector family IPI-O. While the majority of IPI-O proteins are recognized by RB to elicit resistance (e.g. IPI-O1, IPI-O2), some family members are able to elude detection (e.g. IPI-O4). In addition, IPI-O4 blocks recognition of IPI-O1, leading to inactivation of RB-mediated programmed cell death. Here, we report results that elucidate molecular mechanisms governing resistance elicitation or suppression of RB by IPI-O. Our data indicate self-association of the RB coiled coil (CC) domain as well as a physical interaction between this domain and the effectors IPI-O4 and IPI-O1. We identified four amino acids within IPI-O that are critical for interaction with the RB CC domain and one of these amino acids, at position 129, determines hypersensitive response (HR) elicitation in planta. IPI-O1 mutant L129P fails to induce HR in presence of RB while IPI-O4 P129L gains the ability to induce an HR. Like IPI-O4, IPI-O1 L129P is also able to suppress the HR mediated by RB, indicating a critical step in the evolution of this gene family. Our results point to a model in which IPI-O effectors can affect RB function through interaction with the RB CC domain.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Inter- and intramolecular interactions between RB protein domains and IPI-O effectors.

A) Yeast two-hybrid interactions between domains of RB or domain self-association; B) Interactions between domains of RB and IPI-O1 or IPI-O4; C) Results of co-immunoprecipitation of RB CC domain with IPI-O fusion proteins. The indicated protein combinations were expressed in N. benthamiana leaves and total proteins were incubated with green fluorescent protein (GFP) antibody and agarose beads. Precipitated proteins were detected using Myc-tag antibody. Proteins with no fusion or with a hemagglutinin (HA) tag were used as negative controls.

Figure 2
Figure 2. Interactions between RB-like CC domains from potato species with either IPI-O1 or IPI-O4.

The three-letter abbreviation for each species is shown. Numbers after the species name represents the PCR clone number. + and − signs to the right of the yeast colonies indicate positive or negative interaction, respectively. Photos were taken after 8 days of growth on selective media. Photos represent the results of three independent yeast transformations.

Figure 3
Figure 3. Yeast two-hybrid interactions between the CC domain of RB and IPI-O1/4 single and double amino acid mutants.

+ and − signs to the right of the yeast colonies indicate positive or negative interaction, respectively. Pictures were taken after 8 days of growth on selective media. All the experiments were performed three times.

Figure 4
Figure 4. Induction of hypersensitive cell death by IPI-O1 and IPI-O4 mutants in planta.

A. tumefaciens strains expressing IPI-O, IPI-O mutants, or the indicated controls were infiltrated into leaves of RB transgenic N. benthamiana plants. Leaves were photographed at 6 days after infiltration.

Figure 5
Figure 5. Suppression of hypersensitive cell death of IPI-O1 by IPI-O1 L129P and IPI-O4 P129L/G135S (double mutant) by IPI-O4.

A. tumefaciens strains expressing the indicated IPI-O variants or a GFP control were infiltrated or co-infiltrated into leaves of RB transgenic N. benthamiana plants. Leaves were photographed at 6 days after infiltration.

Figure 6
Figure 6. Model for RB/IPI-O interactions.

The top panel represents a resistance response. In the absence of IPI-O1, RB remains in a resting state. The presence of IPI-O1 elicits a conformational change that enables RB oligomerization through the CC domain and leads to an activated protein state. As shown in the bottom panel, when IPI-O4 is present, this effector interacts with the CC domain and prevents CC oligomerization, thus suppressing RB activation.

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References

    1. Dangl JL, Jones JD. Plant pathogens and integrated defence responses to infection. Nature. 2001;411:826–833. - PubMed
    1. Bent AF, Mackey D. Elicitors, effectors, and R genes: The new paradigm and a lifetime supply of questions. Ann Rev Phytopathol. 2007;45:399–436. - PubMed
    1. Chisholm ST, Coaker G, Day B, Staskawicz BJ. Host-microbe interactions: shaping the evolution of the plant immune response. Cell. 2006;124:803–814. - PubMed
    1. He P, Shan L, Lin N-C, Martin GB, Kemmerling B, et al. Specific bacterial suppressors of MAMP signaling upstream of MAPKKK in Arabidopsis innate immunity. Cell. 2006;125:563–575. - PubMed
    1. Nomura K, DebRoy S, Lee YH, Pumplin N, Jones J, et al. A bacterial virulence protein suppresses host innate immunity to cause plant disease. Science. 2006;313:220–223. - PubMed

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