Transcript expression levels of apple allergens in Granny Smith and Golden Delicious fruits across European retail stores

The complex interplay between genetics and environmental factors shapes the allergenic potential of apples. All 4 described allergens of apples vary in their protein content, but the variability at the transcriptomic level is not well known. In this study, the natural variability of the transcriptomic levels of apple genes for allergen isoforms was analysed for fruits from retail chains in various European countries. Real-time quantitative polymerase chain reaction (RT-qPCR) was utilised to quantify the expression of PR-10 (Bet v 1 family), thaumatin-like proteins, nsLTP1 and profilins. The expression levels exhibited variability among apples originating from different countries, to varying degrees. Only minor variation was observed in Golden Delicious, with a change of 0.11-fold to 6.82-fold relative to the calibrator that was the fruit from the Slovak Republic. Among the Mal d 1 isoforms, Mal d 1.02 showed the highest fold change and the greatest variability. However, in Granny Smith, the Mal d 4.01 exhibited substantial up-regulation, reaching approximately 280-fold. Furthermore, the fold changes demonstrated greater variability compared to those observed in Golden Delicious. Insights into the molecular variability and regulation of Mal d 1 isoforms can inform both public health guidance and precision agriculture strategies. As food allergies continue to rise globally, region-specific allergen profiling and cultivar selection may contribute to safer, more transparent and more inclusive food systems.