Difference in accumulation pattern of the allergens within the same PR10 family in transgenic rice

Apple food allergen Mal d 1 and birch pollen allergen Bet v 1 belong to the same pathogen related protein 10 (PR10) family. When each of these allergens was expressed as a secretory protein by fusion with the GFP reporter in transgenic rice by ligating an N terminal signal peptide and a C terminal KDEL ER retention signal under the control of the maize ubiquitin constitutive promoter, the GFP:Mald1 highly accumulated in various tissues, whereas the accumulation level of GFP:Betv1 was remarkably reduced in vegetative tissues except for seed. Analysis by RT-PCR exhibited that there was little difference in transcript levels between them, indicating the involvement of post-transcriptional regulation. To investigate the cause of such difference in accumulation levels, deletion analysis of the Mal d 1 and domain swapping between them were carried out in transgenic rice. These results showed that the region between positions 41-90 in the Mal d 1 is predominantly implicated in higher level accumulation in vegetative tissues as well as seed compared with the Bet v 1. It is notable that GFP:Mald1 directed by the ubiquitin promoter is deposited in huge PBs in aleurone layer rather than starchy endosperm.