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Genetic architecture and pleiotropy shape costs of Rps2-mediated resistance in Arabidopsis thaliana.

ABSTRACT: The mounting evidence that R genes incur large fitness costs raises a question: how can there be a 5-10% fitness reduction for all 149 R genes in the Arabidopsis thaliana genome? The R genes tested to date segregate for insertion-deletion (indel) polymorphisms where susceptible alleles are complete deletions. Since costs of resistance are measured as the differential fitness of isolines carrying resistant and susceptible alleles, indels reveal costs that may be masked when susceptible alleles are expressed. Rps2 segregates for two expressed clades of alleles, one resistant and one susceptible. Plants with resistant Rps2 are not less fit than those with a susceptible Rps2 allele in the absence of disease. Instead, all alleles provide a fitness benefit relative to an artificial deletion because of the role of RPS2 as a negative regulator of defence. Our results highlight the interplay between genomic architecture and the magnitude of costs of resistance.

SUBMITTER: MacQueen A

PROVIDER: S-EPMC4968571 | biostudies-literature | 2016 Jul

REPOSITORIES: biostudies-literature

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Genetic architecture and pleiotropy shape costs of Rps2-mediated resistance in Arabidopsis thaliana.

MacQueen Alice A Sun Xiaoqin X Bergelson Joy J

Nature plants 20160718

The mounting evidence that R genes incur large fitness costs raises a question: how can there be a 5-10% fitness reduction for all 149 R genes in the Arabidopsis thaliana genome? The R genes tested to date segregate for insertion-deletion (indel) polymorphisms where susceptible alleles are complete deletions. Since costs of resistance are measured as the differential fitness of isolines carrying resistant and susceptible alleles, indels reveal costs that may be masked when susceptible alleles ar ...[more]

PMID: 27428524

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Project description:Plants recognize microbes via specific pattern recognition receptors that are activated by microbe-associated molecular patterns (MAMPs), resulting in MAMP-triggered immunity (MTI). Successful pathogens bypass MTI in genetically diverse hosts via deployment of effectors (virulence factors) that inhibit MTI responses, leading to pathogen proliferation. Plant pathogenic bacteria like Pseudomonas syringae utilize a type III secretion system to deliver effectors into cells. These effectors can contribute to pathogen virulence or elicit disease resistance, depending upon the host plant genotype. In disease resistant genotypes, intracellular immune receptors, typically belonging to the nucleotide binding leucine-rich repeat family of proteins, perceive bacterial effector(s) and initiate downstream defense responses (effector triggered immunity) that include the hypersensitive response, and transcriptional re-programming leading to various cellular outputs that collectively halt pathogen growth. Nucleotide binding leucine-rich repeat sensors can be indirectly activated via perturbation of a host protein acting as an effector target. AvrRpm1 is a P. syringae type III effector. Upon secretion into the host cell, AvrRpm1 is acylated by host enzymes and directed to the plasma membrane, where it contributes to virulence. This is correlated with phosphorylation of Arabidopsis RIN4 in vivo. RIN4 is a negative regulator of MAMP-triggered immunity, and its modification in the presence of four diverse type III effectors, including AvrRpm1, likely enhances this RIN4 regulatory function. The RPM1 nucleotide binding leucine-rich repeat sensor perceives RIN4 perturbation in disease resistant plants, leading to a successful immune response. Here, demonstrate that AvrRpm1 has a fold homologous to the catalytic domain of poly(ADP-ribosyl) polymerase. Site-directed mutagenesis of each residue in the putative catalytic triad, His63-Tyr122-Asp185 of AvrRpm1, results in loss of both AvrRpm1-dependent virulence and AvrRpm1-mediated activation of RPM1, but, surprisingly, causes a gain of function: the ability to activate the RPS2 nucleotide binding leucine-rich repeat sensor.

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Dataset Information

Genetic architecture and pleiotropy shape costs of Rps2-mediated resistance in Arabidopsis thaliana.

Publications

Genetic architecture and pleiotropy shape costs of Rps2-mediated resistance in Arabidopsis thaliana.

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