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.