title: Production of calcium oxalate crystals by the basidiomycete Moniliophthora perniciosa, the causal agent of witches' broom disease of Cacao.
abstract: Oxalic acid has been shown as a virulence factor for some phytopathogenic fungi, removing calcium from pectin and favoring plant cell wall degradation. Recently, it was published that calcium oxalate accumulates in infected cacao tissues during the progression of Witches' Broom disease (WBD). In the present work we report that the hemibiotrophic basidiomycete Moniliophthora perniciosa, the causal agent of WBD, produces calcium oxalate crystals. These crystals were initially observed by polarized light microscopy of hyphae growing on a glass slide, apparently being secreted from the cells. The analysis was refined by Scanning electron microscopy and the compositon of the crystals was confirmed by energy-dispersive x-ray spectrometry. The production of oxalate by M. perniciosa was reinforced by the identification of a putative gene coding for oxaloacetate acetylhydrolase, which catalyzes the hydrolysis of oxaloacetate to oxalate and acetate. This gene was shown to be expressed in the biotrophic-like mycelia, which in planta occupy the intercellular middle-lamella space, a region filled with pectin. Taken together, our results suggest that oxalate production by M. perniciosa may play a role in the WBD pathogenesis mechanism.
authors.affiliation: Departamento de Genética e Evolução, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, 13083-970, São Paulo, Brazil.
authors.forename: Maria Carolina S do
authors.initials: MC
authors.lastname: Rio
authors.forename: Bruno V
authors.initials: BV
authors.lastname: de Oliveira
authors.forename: Daniela P T
authors.initials: DP
authors.lastname: de Tomazella
authors.forename: José A Fracassi da
authors.initials: JA
authors.lastname: Silva
authors.forename: Gonçalo A G
authors.initials: GA
authors.lastname: Pereira
mesh_terms: D000363:Agaricales / Q000737:chemistry / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002099:Cacao / Q000382:microbiology*; D002129:Calcium Oxalate / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics; D006867:Hydrolases / Q000235:genetics; D025301:Hyphae / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D008859:Microscopy, Polarization; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000382:microbiology*; D016415:Sequence Alignment; D013052:Spectrometry, X-Ray Emission
chemical_list: D005656:Fungal Proteins; D002129:Calcium Oxalate; D006867:Hydrolases; C054172:oxaloacetase