Approximately 2% of the West-European population has an apple allergy. Bycombining genetic data with the results of skin prick tests in allergic patients,more insight has been gained into the involvement of specific allergen genesin this type of allergy. For his thesis at Wageningen University, ZhongshanGao identified and localised genes which are involved in the allergenicity.The results represent a step forward in the identification, breeding and developmentof low allergenic apple varieties.
Apple is the most cultivated fruit crop in temperate areas. Understandingof apple genetics has increased due to the development of genetic maps andtechniques. This provided molecular markers with which seedlings can be testedfor resistance to certain plant diseases. The use of markers for allergy researchis new.
It has previously been proven that apple allergy is caused by one or moreproteins in apple (the so-called Mal d1- till Mal d4-proteins). Mal d1 is themost important allergen in apple. People who are allergic to the Mal d1 proteinfeel itching, prickling and a swelling of the lips, tongue and throat aftereating a fresh apple.
Gao’s thesis explains that the exact identification of the genes involvedin allergenicity is a major challenge for two reasons. Firstly, more allergenscan play a role together. Secondly, patients differ from each other in theirsensitivity to these allergens and their varieties.
The aim of Gao’s study was to trace and characterise the genes whichare decisive for the amino acid compound of the four most important allergenicprotein types. Another goal of the project was to develop genetic markers foralready predicting at the seedling stage whether or not an apple contains allergenicproteins.
Gao found 26 genes, 18 of which coded for the Mal d1 protein. This allergenis especially relevant to patients in North West Europe, who also suffer fromhay fever in the spring as a reaction to birch pollen. Gao’s researchshowed that the Mal d 1 genes are lying on three chromosomes, with the geneson chromosome 16 playing a clear role in the allergenicity. In addition, itappeared that the amount of Mal d1 protein was less important than the aminoacid composition. Until now, medical studies have primarily focused on thequantity.
Partially because of the results of this study and the use of modern technologiessuch as marker assisted breeding and reduction in gene activity, the futuremay bring new less-allergenic apple varieties on the market. These will allowapple allergic patients to eat the fruit without experiencing any discomfort.The results can also be used for genetic research in other fruit crops suchas pear and peach, which contain similar allergens.
Zhongshan Gao collected his doctorate at Wageningen University and ResearchCentre on 30 June with his study “Localization of candidate allergengenes on the apple (Malus domestica) genome and their putative allergenicity”.
Gao’s thesis was part of the EU-SAFE project, a large European interdisciplinaryconsortium, and he is the first person to graduate from the Allergy ConsortiumWageningen. Subsequent studies will take place as part of the EU project ISAFRUIT,within which apple allergy and the making/selection of hypoallergenic cultivarswill form a significant part.
NOTE TO THE EDITOR
More detailed information is available from Luud Gilissen (luud.gilissen@wur.nl /+ 31 (0)317 477168 or +31 (0)371 483078) or Eric van de Weg (eric.vandeweg@wur.nl/+31 (0)371 477281).
Illustrative material can be obtained from Edwin Luijks (edwin.luijks@wur.nl/+31 (0)371 483915).