Genetic dissection of basal defence responsiveness in accessions of Arabidopsis thaliana

Authors

  • SHAKOOR AHMAD,

    1. Rothamsted Research, Centre of Sustainable Pest and Disease Management, West Common, Harpenden, Herts, AL5 2JQ, UK
    2. Plant–Microbe Interactions, Institute of Environmental Biology, Faculty of Science, Utrecht University, 3508 TB Utrecht
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    • Authors who contributed equally to the work.

  • MARIEKE VAN HULTEN,

    1. Plant–Microbe Interactions, Institute of Environmental Biology, Faculty of Science, Utrecht University, 3508 TB Utrecht
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    • Authors who contributed equally to the work.

  • JANET MARTIN,

    1. Rothamsted Research, Centre of Sustainable Pest and Disease Management, West Common, Harpenden, Herts, AL5 2JQ, UK
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  • CORNÉ M. J. PIETERSE,

    1. Plant–Microbe Interactions, Institute of Environmental Biology, Faculty of Science, Utrecht University, 3508 TB Utrecht
    2. Centre for BioSystems Genomics, 6700 AB Wageningen, the Netherlands
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  • SASKIA C. M. VAN WEES,

    1. Plant–Microbe Interactions, Institute of Environmental Biology, Faculty of Science, Utrecht University, 3508 TB Utrecht
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  • JURRIAAN TON

    Corresponding author
    1. Rothamsted Research, Centre of Sustainable Pest and Disease Management, West Common, Harpenden, Herts, AL5 2JQ, UK
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J. Ton. E-mail: jurriaan.ton@bbsrc.ac.uk

ABSTRACT

Basal resistance involves a multitude of pathogen- and herbivore-inducible defence mechanisms, ranging from localized callose deposition to systemic defence gene induction by salicylic acid (SA) and jasmonic acid (JA). In this study, we have explored and dissected genetic variation in the responsiveness of basal defence mechanisms within a selection of Arabidopsis accessions. Responsiveness of JA-induced PDF1.2 gene expression was associated with enhanced basal resistance against the necrotrophic fungus Plectosphaerella cucumerina and the herbivore Spodoptera littoralis. Conversely, accessions showing augmented PR-1 induction upon SA treatment were more resistant to the hemi-biotrophic pathogen Pseudomonas syringae, and constitutively expressed defence-related transcription factor (TF) genes. Unexpectedly, accessions with primed responsiveness to SA deposited comparatively little callose after treatment with microbe-associated molecular patterns. A quantitative trait locus (QTL) analysis identified two loci regulating flagellin-induced callose and one locus regulating SA-induced PR-1 expression. The latter QTL was found to contribute to basal resistance against P. syringae. None of the defence regulatory QTLs influenced plant growth, suggesting that the constitutive defence priming conferred by these loci is not associated with major costs on plant growth. Our study demonstrates that natural variation in basal resistance can be exploited to identify genetic loci that prime the plant's basal defence arsenal.

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