title: ABA is an essential signal for plant resistance to pathogens affecting JA biosynthesis and the activation of defenses in Arabidopsis.
abstract: Analyses of Arabidopsis thaliana defense response to the damping-off oomycete pathogen Pythium irregulare show that resistance to P. irregulare requires a multicomponent defense strategy. Penetration represents a first layer, as indicated by the susceptibility of pen2 mutants, followed by recognition, likely mediated by ERECTA receptor-like kinases. Subsequent signaling of inducible defenses is predominantly mediated by jasmonic acid (JA), with insensitive coi1 mutants showing extreme susceptibility. In contrast with the generally accepted roles of ethylene and salicylic acid cooperating with or antagonizing, respectively, JA in the activation of defenses against necrotrophs, both are required to prevent disease progression, although much less so than JA. Meta-analysis of transcriptome profiles confirmed the predominant role of JA in activation of P. irregulare-induced defenses and uncovered abscisic acid (ABA) as an important regulator of defense gene expression. Analysis of cis-regulatory sequences also revealed an unexpected overrepresentation of ABA response elements in promoters of P. irregulare-responsive genes. Subsequent infections of ABA-related and callose-deficient mutants confirmed the importance of ABA in defense, acting partly through an undescribed mechanism. The results support a model for ABA affecting JA biosynthesis in the activation of defenses against this oomycete.
authors.affiliation: Departamento de Genética Molecular de Plantas, Centro Nacional de Biotecnología-Consejo Superior de Investigaciones Científicas, Campus Universidad Autónoma, 28049 Madrid, Spain.
authors.forename: Bruce A T
authors.initials: BA
authors.lastname: Adie
authors.forename: Julián
authors.initials: J
authors.lastname: Pérez-Pérez
authors.forename: Manuel M
authors.initials: MM
authors.lastname: Pérez-Pérez
authors.forename: Marta
authors.initials: M
authors.lastname: Godoy
authors.forename: José-J
authors.initials: JJ
authors.lastname: Sánchez-Serrano
authors.forename: Eric A
authors.initials: EA
authors.lastname: Schmelz
authors.forename: Roberto
authors.initials: R
authors.lastname: Solano
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000382:microbiology*; D003517:Cyclopentanes / Q000378:metabolism*; D005030:Ethylenes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D007113:Immunity, Innate; D015201:Meta-Analysis as Topic; D009868:Oomycetes / Q000502:physiology*; D054883:Oxylipins; D010802:Phylogeny; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology*; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D020156:Salicylic Acid / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic
chemical_list: D003517:Cyclopentanes; D005030:Ethylenes; D054883:Oxylipins; C011006:jasmonic acid; D000040:Abscisic Acid; C036216:ethylene; D020156:Salicylic Acid