title: Brassinosteroids suppress rice defense against root-knot nematodes through antagonism with the jasmonate pathway.
abstract: The importance of phytohormone balance is increasingly recognized as central to the outcome of plant-pathogen interactions. Next to their well-known developmental role, brassinosteroids (BR) were recently found to be involved in plant innate immunity. In this study, we examined the role of BR in rice (Oryza sativa) innate immunity during infection with the root-knot nematode Meloidogyne graminicola, and we studied the inter-relationship with the jasmonate (JA) pathway. Exogenous epibrassinolide (BL) supply at low concentrations induced susceptibility in the roots whereas high concentrations of BL enforced systemic defense against this nematode. Upon high exogenous BL supply on the shoot, quantitative reverse-transcription polymerase chain reaction (qRT-PCR) confirmed a strong feedback inhibitory effect, leading to reduced BR biosynthesis in the root. Moreover, we demonstrate that the immune suppressive effect of BR is at least partly due to negative cross-talk with the JA pathway. Mutants in the BR biosynthesis or signaling pathway accumulate slightly higher levels of the immediate JA-precursor 12-oxo-phytodienoic acid, and qRT-PCR data showed that the BR and JA pathway are mutually antagonistic in rice roots. Collectively, these results suggest that the balance between the BR and JA pathway is an effective regulator of the outcome of the rice-M. graminicola interaction.
authors.affiliation: Department of Molecular Biotechnology, Ghent University, Ghent, Belgium.
authors.forename: Kamrun
authors.initials: K
authors.lastname: Nahar
authors.forename: Tina
authors.initials: T
authors.lastname: Kyndt
authors.forename: Bettina
authors.initials: B
authors.lastname: Hause
authors.forename: Monica
authors.initials: M
authors.lastname: Höfte
authors.forename: Godelieve
authors.initials: G
authors.lastname: Gheysen
mesh_terms: D000818:Animals; D060406:Brassinosteroids / Q000378:metabolism / Q000494:pharmacology*; D003517:Cyclopentanes / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D025461:Feedback, Physiological; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D008954:Models, Biological; D009154:Mutation; D012275:Oryza / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism / Q000469:parasitology; D054883:Oxylipins / Q000378:metabolism*; D010935:Plant Diseases / Q000276:immunology* / Q000469:parasitology; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology*; D057865:Plant Immunity; D018517:Plant Roots / Q000187:drug effects / Q000276:immunology / Q000378:metabolism / Q000469:parasitology; D018749:RNA, Plant / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D014431:Tylenchoidea / Q000472:pathogenicity* / Q000502:physiology
chemical_list: D060406:Brassinosteroids; D003517:Cyclopentanes; D005231:Fatty Acids, Unsaturated; D054883:Oxylipins; D010937:Plant Growth Regulators; D018749:RNA, Plant; C025999:12-oxophytodienoic acid; C011006:jasmonic acid