title: Cloning of a gene encoding an Alt a 1 isoallergen differentially expressed by the necrotrophic fungus Alternaria brassicicola during Arabidopsis infection.
abstract: Alternaria species are considered some of the most important fungi responsible for allergenic morbidity in humans. The Alternaria protein that elicits the most intense allergic reaction in humans is Alt a 1, yet no biological function has been identified for this protein. In this study, suppression subtractive hybridization and virtual Northern blots were used to identify and characterize an Alt a 1 homolog in the phytopathogenic fungus Alternaria brassicicola. RNA was extracted from A. brassicicola spores germinated in water and on leaf surfaces of the Arabidopsis ecotype Landsberg for 24 h and used to create cDNA by PCR. Double-stranded cDNA was then used in suppression subtractive hybridization to identify differentially expressed genes. mRNA transcript levels were assessed by virtual Northern blotting. A sequence with significant homology (90% amino acid, 92% cDNA) to the Alt a 1 subunit from Alternaria alternata was identified. Virtual Northern blots demonstrated that this homolog, designated Alt b 1 precursor, was highly up-regulated during the infection process of A. brassicicola on Arabidopsis: The full-length cDNA sequence of Alt b 1 was 815 bp, with an open reading frame of 477 bp. In this preliminary study, we identified a homolog of the major Alternaria allergen precursor, Alt a 1, in A. brassicicola, designated Alt b 1. This isoallergen is differentially expressed during fungal pathogenesis on Arabidopsis, suggesting a possible biological role in pathogenesis.
authors.affiliation: Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins 80523-1177, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Cramer
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Lawrence
mesh_terms: D000485:Allergens / Q000235:genetics / Q000378:metabolism*; D000528:Alternaria / Q000235:genetics / Q000254:growth & development / Q000276:immunology / Q000472:pathogenicity*; D000595:Amino Acid Sequence; D000946:Antigens, Fungal; D052179:Antigens, Plant; D017360:Arabidopsis / Q000382:microbiology*; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000382:microbiology; D018515:Plant Leaves / Q000382:microbiology; D017422:Sequence Analysis, DNA; D013172:Spores, Fungal
chemical_list: C096258:ALTA1 protein, Alternaria alternata; C474845:ALTB1 protein, Alternaria brassicicola; D000485:Allergens; D000946:Antigens, Fungal; D052179:Antigens, Plant; D018076:DNA, Complementary; D005656:Fungal Proteins