title: A mutation in the expansin-like A2 gene enhances resistance to necrotrophic fungi and hypersensitivity to abiotic stress in Arabidopsis thaliana.
abstract: Expansins are cell wall loosening agents, known for their endogenous function in cell wall extensibility. The Arabidopsis expansin-like A2 (EXLA2) gene was identified by its down-regulation in response to infection by the necrotrophic pathogen Botrytis cinerea, and by the reduced susceptibility of an exla2 mutant to the same pathogen. The exla2 mutant was equally susceptible to Pseudomonas syringae pv. tomato, but was more resistant to the necrotrophic fungus Alternaria brassicicola, when compared with the wild-type or with transgenic, ectopic EXLA2-overexpressing lines. The exla2 mutants also enhanced tolerance to the phytoprostane-A1 . This suggests that the absence or down-regulation of EXLA2 leads to increased resistance to B. cinerea in a CORONATINE INSENSITIVE 1 (COI1)-dependent manner, and this down-regulation can be achieved by phytoprostane-A1 treatment. EXLA2 is induced significantly by salinity and cold, and by the exogenous application of abscisic acid. The exla2 mutant also showed hypersensitivity towards increased salt and cold, and this hypersensitivity required a functional abscisic acid pathway. The differential temporal expression of EXLA2 and the phenotypes in transgenic plants with altered expression of EXLA2 indicate that plant cell wall structure is an important player during Arabidopsis developmental stages. Our results indicate that EXLA2 appears to be important in response to various biotic and abiotic stresses, particularly in the pathogenesis of necrotrophic pathogens and in the tolerance to abiotic stress.
authors.affiliation: Department of Biology, College of Science, United Arab Emirates University, PO Box 15551, Al-Ain, United Arab Emirates. sabuqamar@uaeu.ac.ae
authors.forename: Synan
authors.initials: S
authors.lastname: Abuqamar
authors.forename: Suad
authors.initials: S
authors.lastname: Ajeb
authors.forename: Arjun
authors.initials: A
authors.lastname: Sham
authors.forename: Mohamed Rizq
authors.initials: MR
authors.lastname: Enan
authors.forename: Rabah
authors.initials: R
authors.lastname: Iratni
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D000222:Adaptation, Physiological / Q000187:drug effects / Q000235:genetics; D000528:Alternaria / Q000187:drug effects / Q000502:physiology*; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000276:immunology / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D020171:Botrytis / Q000187:drug effects / Q000502:physiology; D003080:Cold Temperature; D003517:Cyclopentanes / Q000494:pharmacology; D060467:Disease Resistance / Q000235:genetics* / Q000276:immunology; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D035264:Flowers / Q000187:drug effects / Q000502:physiology; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D009154:Mutation / Q000235:genetics*; D018384:Oxidative Stress / Q000187:drug effects; D010641:Phenotype; D010935:Plant Diseases / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D003517:Cyclopentanes; C000588566:EXLA2 protein, Arabidopsis; D012333:RNA, Messenger; D012965:Sodium Chloride; D000040:Abscisic Acid