title: Increased resistance against citrus canker mediated by a citrus mitogen-activated protein kinase.
abstract: Mitogen-activated protein kinases (MAPK) play crucial roles in plant immunity. We previously identified a citrus MAPK (CsMAPK1) as a differentially expressed protein in response to infection by Xanthomonas aurantifolii, a bacterium that causes citrus canker in Mexican lime but a hypersensitive reaction in sweet oranges. Here, we confirm that, in sweet orange, CsMAPK1 is rapidly and preferentially induced by X. aurantifolii relative to Xanthomonas citri. To investigate the role of CsMAPK1 in citrus canker resistance, we expressed CsMAPK1 in citrus plants under the control of the PR5 gene promoter, which is induced by Xanthomonas infection and wounding. Increased expression of CsMAPK1 correlated with a reduction in canker symptoms and a decrease in bacterial growth. Canker lesions in plants with higher CsMAPK1 levels were smaller and showed fewer signs of epidermal rupture. Transgenic plants also revealed higher transcript levels of defense-related genes and a significant accumulation of hydrogen peroxide in response to wounding or X. citri infection. Accordingly, nontransgenic sweet orange leaves accumulate both CsMAPK1 and hydrogen peroxide in response to X. aurantifolii but not X. citri infection. These data, thus, indicate that CsMAPK1 functions in the citrus canker defense response by inducing defense gene expression and reactive oxygen species accumulation during infection.
authors.forename: Maria Luiza Peixoto
authors.initials: ML
authors.lastname: de Oliveira
authors.forename: Caio Cesar
authors.initials: CC
authors.lastname: de Lima Silva
authors.forename: Valéria Yukari
authors.initials: VY
authors.lastname: Abe
authors.forename: Marcio Gilberto Cardoso
authors.initials: MG
authors.lastname: Costa
authors.forename: Raúl Andrés
authors.initials: RA
authors.lastname: Cernadas
authors.forename: Celso Eduardo
authors.initials: CE
authors.lastname: Benedetti
mesh_terms: D032082:Citrus aurantiifolia / Q000235:genetics / Q000254:growth & development / Q000276:immunology* / Q000382:microbiology; D032084:Citrus sinensis / Q000235:genetics / Q000254:growth & development / Q000276:immunology* / Q000382:microbiology; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D006861:Hydrogen Peroxide / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D019441:Plant Epidermis; D057865:Plant Immunity; D018515:Plant Leaves; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D014974:Xanthomonas / Q000472:pathogenicity / Q000502:physiology*
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D020928:Mitogen-Activated Protein Kinases