Genomic organisation of the Mal d 1 gene cluster on linkage group 16 in apple

European populations exhibit progressive sensitisation to food allergens, and apples are one of the foods for which sensitisation is observed most frequently. Apple cultivars vary greatly in their allergenic characteristics, and a better understanding of the genetic basis of low allergenicity may therefore allow allergic individuals to increase their fruit intake. Mal d 1 is considered to be a major apple allergen, and this protein is encoded by the most complex allergen gene family. Not all Mal d 1 members are likely to be involved in allergenicity. Therefore, additional knowledge about the existence and characteristics of the different Mal d 1 genes is required. In the present study, we investigated the genomic organisation of the Mal d 1 gene cluster in linkage group 16 of apple through the sequencing of two bacterial artificial chromosome clones. The results provided new information on the composition of this family with respect to the number and orientation of functional and pseudogenes and their physical distances. The results were compared with the apple and peach genome sequences that have recently been made available. A broad analysis of the whole apple genome revealed the presence of new genes in this family, and a complete list of the observed Mal d 1 genes is supplied. Thus, this study provides an important contribution towards a better understanding of the genetics of the Mal d 1 family and establishes the basis for further research on allelic diversity among cultivars in relation to variation in allergenicit