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pubmed:abstractText |
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.
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