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

Abstract

Fra a 1 is a strawberry allergen that causes oral allergic syndrome. Fra a 1.01 is a major isoform that accumulates abundantly in fruits during the winter season. Here, we tested the hypothesis that Fra a 1.01 responds to environmental factors, such as cold stress. We analyzed transcriptional and translational levels of Fra a 1.01 in strawberry calli and organs under various cold conditions. First, we incubated strawberry (Fragaria × ananassa 'Akihime') calli and post-harvested fruits at low temperatures from several hours to days. Fra a 1.01 did not show significant differences in either gene expression or protein accumulation levels, suggesting that short-term cold treatments did not affect Fra a 1.01 expression. Second, we exposed whole plants to low temperature conditions for ~28 days. Under conditions below 10°C, Fra a 1.01 transcripts were induced gradually throughout the cold treatment (crown and root), or from 2 days to the last day (leaf and fruit). The Fra a 1.01 protein remarkably accumulated in crowns and slightly in fruits after 28 days. Finally, the promoter region of Fra a 1.01e was analyzed to detect tissue-specific expression. The cloned and sequenced promoter included several cis-acting regulatory elements related to cold response. When the Fra a 1.01 promoter region was heterologously expressed in Arabidopsis, the promoter activities, as assessed by GUS staining, were observed mainly around the shoot apices and in roots. Thus, Fra a 1.01 was considered to be expressed in crowns and roots, and was additively induced by cold stress. These organ-specific expressions could be important in elucidating the mechanisms responsible for Fra a 1.01 protein's accumulation in fruits during the winter season.

Characteristics of major allergen Fra a 1 in cultivated strawberry

“…A similar trend is observed in Italy, where Fra a 1 content is high when the temperature rise at the ripening stage is slow [49]. In the whole plants, Fra a 1.01 transcript is first induced in the crown and root when the plants are exposed to low-temperature conditions during long-term cultivation [48].…”

“…Heat treatment of post-harvest strawberry extracts also slightly induces Fra a 1 content [31]. However, in low-temperature conditions, both Fra a 1.01 transcript and protein in harvested fruit are not affected when exposed to cold conditions after harvest [48].…”

“…At this time, infected plants accumulate antifungal secondary metabolites and phytohormones. [48,50] harvesting in lowtemperature season protein 1.01 and undefined up "Akihime", WH1, "Adria", "Svera" fruit (green, pink, red, ripe) [32,49] chilled storage protein 1.01 n.s. "Akihime" fruit (ripe) [48] * "n.s."…”

“…[48,50] harvesting in lowtemperature season protein 1.01 and undefined up "Akihime", WH1, "Adria", "Svera" fruit (green, pink, red, ripe) [32,49] chilled storage protein 1.01 n.s. "Akihime" fruit (ripe) [48] * "n.s." indicates "not significant differences".…”

Pre- and Post-Harvest Conditions Affect Polyphenol Content in Strawberry (Fragaria × ananassa)

“…First, we screened one to two samples from each experimental plot (Figure S1). Considering the variation within a treatment, we selected three for pre-harvest treatment, and four for post-harvest treatment (Table 1) [18,19]. Only one case showed significant differences in the total polyphenol content among the post-harvest experimental plots.…”