Seasonal Variation of the Major Allergen Fra a 1 in Strawberry Fruit

Abstract

Strawberry (Fragaria × ananassa) contains a major allergen, Fra a 1, which causes oral allergic syndrome. Fra a 1 is a PR-10 homolog that is regulated by environmental conditions. The allergenicity of fruit caused by Fra a 1 may depend on the genotype or growing conditions. We analyzed the Fra a 1.01 transcript levels and Fra a 1.01 protein levels in strawberry fruits of several genotypes across all seasons. In the preliminary rough screening, we selected the line WH1 bearing white fruit and the red-fruited cultivar ‘Akihime’. Under the same environmental conditions, there was no significant difference in Fra a 1.01 levels between the two cultivars over several months, suggesting that receptacle color was not indicative of allergenicity caused by Fra a 1.01. Fruits cultivated under the same environmental conditions should be used for comparisons of the allergenicity among genotypes. Both ‘Akihime’ and WH1 accumulated significantly higher levels of Fra a 1.01 protein in winter than in spring. We investigated the effects of irradiation and low temperature as environmental factors controlling the accumulation of Fra a 1.01 in winter. A shading treatment on fruit did not significantly affect Fra a 1.01 protein accumulation in strawberry fruits. Regarding variations over time, the Fra a 1.01 protein content was higher in fruits harvested at midnight in January than in those harvested at other times and in other months. These findings suggested that the Fra a 1.01 protein accumulates in response to environmental factors such as cold stress.