title: Genetic dissection of basal defence responsiveness in accessions of Arabidopsis thaliana.
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.
authors.affiliation: Rothamsted Research, Centre of Sustainable Pest and Disease Management, West Common, Harpenden, Herts, UK.
authors.forename: Shakoor
authors.initials: S
authors.lastname: Ahmad
authors.forename: Marieke
authors.initials: M
authors.lastname: Van Hulten
authors.forename: Janet
authors.initials: J
authors.lastname: Martin
authors.forename: Corné M J
authors.initials: CM
authors.lastname: Pieterse
authors.forename: Saskia C M
authors.initials: SC
authors.lastname: Van Wees
authors.forename: Jurriaan
authors.initials: J
authors.lastname: Ton
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000235:genetics* / Q000276:immunology / Q000382:microbiology / Q000469:parasitology; D029681:Arabidopsis Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D001203:Ascomycota / Q000472:pathogenicity; D032461:Chromosomes, Plant / Q000235:genetics; D003517:Cyclopentanes / Q000494:pharmacology; D023082:Defensins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D005247:Feeding Behavior; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D005936:Glucans / Q000378:metabolism; D007113:Immunity, Innate; D007814:Larva / Q000254:growth & development / Q000472:pathogenicity; D054883:Oxylipins / Q000494:pharmacology; D010454:Peptide Termination Factors / Q000235:genetics / Q000378:metabolism; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology / Q000469:parasitology; D018515:Plant Leaves / Q000187:drug effects / Q000382:microbiology / Q000469:parasitology; D011110:Polymorphism, Genetic; D011549:Pseudomonas / Q000472:pathogenicity; D040641:Quantitative Trait Loci; D020156:Salicylic Acid / Q000494:pharmacology; D018411:Spodoptera / Q000472:pathogenicity; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D003517:Cyclopentanes; D023082:Defensins; D005936:Glucans; D054883:Oxylipins; D010454:Peptide Termination Factors; D020156:Salicylic Acid; D014157:Transcription Factors; C531343:ORA59 protein, Arabidopsis; C487542:At5g44420 protein, Arabidopsis; C463539:VSP2 protein, Arabidopsis; C494978:eukaryotic release factor 1, Arabidopsis; C077262:PR-1 protein, Arabidopsis; C011006:jasmonic acid; C048306:callose