Identification, characterization and epitope mapping of proteins encoded by putative allergenic napin genes from Brassica rapa.

Brassica rapeseed crops contain high concentrations of oil in the seed. The remaining meal, following oil extraction, has a high protein-content, but is of low value due to the presence of high amounts of napin seed storage proteins. These 2S albumin-like proteins are difficult to digest and have been identified as major allergens in humans.To comprehensively characterise the napin gene (NG) family in Brassica rapa and to gain an understanding of the structural basis of allergenicity of the expressed proteins.To identify candidate napin gene in B. rapa, 2S albumin like napin genes of Arabidopsis thaliana were used as query sequences to search for similarity against the B. rapa var. pekinesis Chiifu-401, v2 and the var. trilocularis R-o-18 v1.5 genomes. Multiple sequence alignment (MSA) and epitope modelling was carried out to determine structural and evolutionary relationships of NGs and their potential allergenicity.Ten candidate napin genes in R-o-18 and four in Chiifu-401 were identified with high sequence similarity to A. thaliana napin genes. Multiple sequence alignment revealed strong conservation among the candidate genes. An epitope survey indicated high conservation of allergenic epitope motifs with known 2S albumin like allergens.Napin is thought to be responsible for the high prevalence of rapeseed allergies. Characterisation of the napin gene family in B. rapa will give important insight into the protein structure and epitope-modelling will help to advance studies into allergenicity including the development of precise diagnostic screenings and therapies for rapeseed allergy as well as the possible manipulation of napin levels in the seed by gene editing technology.