title: Layers of defense responses to Leptosphaeria maculans below the RLM1- and camalexin-dependent resistances.
abstract: Plants have evolved different defense components to counteract pathogen attacks. The resistance locus resistance to Leptosphaeria maculans 1 (RLM1) is a key factor for Arabidopsis thaliana resistance to L. maculans. The present work aimed to reveal downstream defense responses regulated by RLM1. Quantitative assessment of fungal colonization in the host was carried out using quantitative polymerase chain reaction (qPCR) and GUS expression analyses, to further characterize RLM1 resistance and the role of salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) in disease development. Additional assessments of A. thaliana mutants were performed to expand our understanding of this pathosystem. Resistance responses such as lignification and the formation of vascular plugs were found to occur in an RLM1-dependent manner, in contrast to the RLM1-independent increase in reactive oxygen species at the stomata and hydathodes. Analyses of mutants defective in hormone signaling in the camalexin-free rlm1(Ler)pad3 background revealed a significant influence of JA and ET on symptom development and pathogen colonization. The overall results indicate that the defense responses of primary importance induced by RLM1 are all associated with physical barriers, and that responses of secondary importance involve complex cross-talk among SA, JA and ET. Our observations further suggest that ET positively affects fungal colonization.
authors.affiliation: Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, PO Box 7080, 750 07 Uppsala, Sweden.
authors.forename: Mattias
authors.initials: M
authors.lastname: Persson
authors.affiliation: Department of Molecular Biomedical Research, Unit for Molecular Signal Transduction in Inflammation, VIB, Technologiepark 927, B-9052 Ghent (Zwijnaarde), Belgium.|Department of Molecular Biology, Ghent University, Technologiepark 927, B-9052 Ghent (Zwijnaarde), Belgium.
authors.forename: Jens
authors.initials: J
authors.lastname: Staal
authors.affiliation: Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, PO Box 7080, 750 07 Uppsala, Sweden.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Oide
authors.affiliation: Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, PO Box 7080, 750 07 Uppsala, Sweden.
authors.forename: Christina
authors.initials: C
authors.lastname: Dixelius
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics; D003517:Cyclopentanes; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D005030:Ethylenes; D005658:Fungi / Q000472:pathogenicity*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D054884:Host-Pathogen Interactions / Q000235:genetics*; D007211:Indoles / Q000378:metabolism*; D008031:Lignin / Q000378:metabolism; D054883:Oxylipins; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D010937:Plant Growth Regulators / Q000235:genetics*; D020156:Salicylic Acid; D015398:Signal Transduction; D013844:Thiazoles / Q000378:metabolism*; D037521:Virulence Factors; D000094162:Phytoalexins
chemical_list: D029681:Arabidopsis Proteins; D003517:Cyclopentanes; D003577:Cytochrome P-450 Enzyme System; D005030:Ethylenes; D007211:Indoles; D008031:Lignin; D054883:Oxylipins; D010937:Plant Growth Regulators; D020156:Salicylic Acid; D013844:Thiazoles; D037521:Virulence Factors; C102405:camalexin; D000094162:Phytoalexins; C011006:jasmonic acid; C036216:ethylene; C417307:PAD3 protein, Arabidopsis