title: Hydrogen peroxide formation in cacao tissues infected by the hemibiotrophic fungus Moniliophthora perniciosa.
abstract: In plant-pathogen interaction, the hydrogen peroxide (H₂O₂) may play a dual role: its accumulation inhibits the growth of biotrophic pathogens, while it could help the infection/colonization process of plant by necrotrophic pathogens. One of the possible pathways of H₂O production involves oxalic acid (Oxa) degradation by apoplastic oxalate oxidase. Here, we analyzed the production of H₂O₂, the presence of calcium oxalate (CaOx) crystals and the content of Oxa and ascorbic acid (Asa)--the main precursor of Oxa in plants--in susceptible and resistant cacao (Theobroma cacao L.) infected by the hemibiotrophic fungus Moniliophthora perniciosa. We also quantified the transcript level of ascorbate peroxidase (Apx), germin-like oxalate oxidase (Glp) and dehydroascorbate reductase (Dhar) by RT-qPCR. We report that the CaOx crystal amount and the H₂O₂ levels in the two varieties present distinct temporal and genotype-dependent patterns. Susceptible variety accumulated more CaOx crystals than the resistant one, and the dissolution of these crystals occurred in the early infection steps and in the final stage of the disease in the resistant and the susceptible variety, respectively. High expression of the Glp and accumulation of Oxa were observed in the resistant variety. The content of Asa increased in the inoculated susceptible variety, but remained constant in the resistant one. The susceptible variety presented reduced Dhar expression. The role of H₂O₂ and its formation from Oxa via Apx and Glp in resistant and susceptible variety infected by M. perniciosa were discussed.
authors.affiliation: UESC, DCB, Centro de Biotecnologia e Genética, Rodovia Ilhéus-Itabuna Km 16, 45662-900 Ilhéus-BA, Brazil.
authors.forename: Cristiano Villela
authors.initials: CV
authors.lastname: Dias
authors.forename: Juliano Sales
authors.initials: JS
authors.lastname: Mendes
authors.forename: Anderson Carvalho
authors.initials: AC
authors.lastname: dos Santos
authors.forename: Carlos Priminho
authors.initials: CP
authors.lastname: Pirovani
authors.forename: Abelmon
authors.initials: A
authors.lastname: da Silva Gesteira
authors.forename: Fabienne
authors.initials: F
authors.lastname: Micheli
authors.forename: Karina Peres
authors.initials: KP
authors.lastname: Gramacho
authors.forename: John
authors.initials: J
authors.lastname: Hammerstone
authors.forename: Paulo
authors.initials: P
authors.lastname: Mazzafera
authors.forename: Júlio Cézar
authors.initials: JC
authors.lastname: de Mattos Cascardo
mesh_terms: D000363:Agaricales / Q000472:pathogenicity*; D060387:Ascorbate Peroxidases / Q000235:genetics / Q000378:metabolism; D001205:Ascorbic Acid / Q000378:metabolism; D002099:Cacao / Q000378:metabolism / Q000382:microbiology*; D002129:Calcium Oxalate / Q000378:metabolism; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006861:Hydrogen Peroxide / Q000378:metabolism*; D019815:Oxalic Acid / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010935:Plant Diseases / Q000382:microbiology; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D002129:Calcium Oxalate; D019815:Oxalic Acid; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; D060387:Ascorbate Peroxidases; C020598:oxalate oxidase; C020666:glutathione dehydrogenase (ascorbate); D001205:Ascorbic Acid