title: Characterisation of a flavonoid ligand of the fungal protein Alt a 1.
abstract: Spores of pathogenic fungi are virtually ubiquitous and cause human disease and severe losses in crops. The endophytic fungi Alternaria species produce host-selective phytotoxins. Alt a 1 is a strongly allergenic protein found in A. alternata that causes severe asthma. Despite the well-established pathogenicity of Alt a 1, the molecular mechanisms underlying its action and physiological function remain largely unknown. To gain insight into the role played by this protein in the pathogenicity of the fungus, we studied production of Alt a 1 and its activity in spores. We found that Alt a 1 accumulates inside spores and that its release with a ligand is pH-dependent, with optimum production in the 5.0-6.5 interval. The Alt a 1 ligand was identified as a methylated flavonoid that inhibits plant root growth and detoxifies reactive oxygen species. We also found that Alt a 1 changes its oligomerization state depending on the pH of the surrounding medium and that these changes facilitate the release of the ligand. Based on these results, we propose that release of Alt a 1 should be a pathogenic target in approaches used to block plant defenses and consequently to favor fungal entry into the plant.
authors.affiliation: Centre for Plant Biotechnology and Genomics (UPM-INIA), Pozuelo de Alarcón, Madrid, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Garrido-Arandia
authors.affiliation: Centre for Plant Biotechnology and Genomics (UPM-INIA), Pozuelo de Alarcón, Madrid, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Silva-Navas
authors.affiliation: Centre for Plant Biotechnology and Genomics (UPM-INIA), Pozuelo de Alarcón, Madrid, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Ramírez-Castillejo
authors.affiliation: Centre for Plant Biotechnology and Genomics (UPM-INIA), Pozuelo de Alarcón, Madrid, Spain.
authors.forename: Nuria
authors.initials: N
authors.lastname: Cubells-Baeza
authors.affiliation: Lund University, Department of Experimental Medical Sciences, Lund, Sweden.
authors.forename: Cristina
authors.initials: C
authors.lastname: Gómez-Casado
authors.affiliation: Institute of Applied Molecular Medicine (IMMA), CEU San Pablo University, Spain.
authors.forename: Domingo
authors.initials: D
authors.lastname: Barber
authors.affiliation: Centre for Plant Biotechnology and Genomics (UPM-INIA), Pozuelo de Alarcón, Madrid, Spain.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Pozo
authors.affiliation: Centre for Plant Biotechnology and Genomics (UPM-INIA), Pozuelo de Alarcón, Madrid, Spain.
authors.forename: Pablo G
authors.initials: PG
authors.lastname: Melendi
authors.affiliation: Centre for Plant Biotechnology and Genomics (UPM-INIA), Pozuelo de Alarcón, Madrid, Spain.|Department of Natural Systems and Resources, ETSI Montes, Technical University of Madrid, Madrid, Spain.
authors.forename: Luis F
authors.initials: LF
authors.lastname: Pacios
authors.affiliation: Centre for Plant Biotechnology and Genomics (UPM-INIA), Pozuelo de Alarcón, Madrid, Spain.
authors.forename: Araceli
authors.initials: A
authors.lastname: Díaz-Perales
mesh_terms: D000485:Allergens / Q000737:chemistry / Q000378:metabolism*; D017360:Arabidopsis / Q000382:microbiology; D002396:Catechols / Q000378:metabolism; D005419:Flavonoids / Q000737:chemistry / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D008745:Methylation; D062105:Molecular Docking Simulation; D018517:Plant Roots / Q000382:microbiology; D011794:Quercetin / Q000494:pharmacology; D013172:Spores, Fungal / Q000378:metabolism
chemical_list: C096258:ALTA1 protein, Alternaria alternata; D000485:Allergens; D002396:Catechols; D005419:Flavonoids; D005656:Fungal Proteins; D008024:Ligands; D011794:Quercetin