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.

Response of the Major Allergen Fra a 1.01 in Strawberry to Cold

“…We revealed a seasonal variation in Fra a 1.01 accumulation, which was especially enhanced in the winter season (Ishibashi et al, 2019b). We hypothesized that Fra a 1.01 transcription and/or the Fra a 1.01 protein responds to cold stress.…”

“…The Fra a 1.01 protein is a major allergen encoded by Fra a 1 paralogs (Ishibashi et al, 2018;Musidlowska-Persson et al, 2007). It accumulates particularly in fruits grown during the winter season (Ishibashi et al, 2019b). Our hypothesis was that the cold might be a key trigger to induce Fra a 1.01 accumulation in the winter.…”

“…Five plantlets were cultivated per plastic container. The containers were filled with general culture soil according to Ishibashi et al (2019b). One of the containers, in which some plantlets bore red fruits after artificial pollination, was transferred to a low-temperature room with fluorescent lighting (from 4 to 10°C, 50 μmol•m −2 •s −1 , photoperiod of 16 h; Fig.…”

“…For protein extraction and fluorometric determination, we mainly followed the protocol of Ishibashi et al (2019b), with some modifications. For the detection of Fra a 1.01, 0.05 μg protein from calli, 0.5 μg protein from fruits, and 0.1 μg protein from leaf blades, crowns, and roots were each dissolved in SDS-PAGE sample buffer.…”

“…Several external stimuli induce Fra a 1 expression, including UV-C radiation, chitosan treatments, and achene removal (Ishibashi et al, 2017;Petriccione et al, 2017;Severo et al, 2015). Differences in Fra a 1 expression levels in varieties have been reported in some cultivation areas (Alm et al, 2007;Franz-Oberdorf et al, 2016); however, differences, as assessed by Fra a 1 protein accumulation levels, have not been documented in various production areas, including Japan (Franz-Oberdorf et al, 2017;Ishibashi et al, 2019b;Kurze et al, 2018).…”