Evaluation of glycine germplasm for nulls of the immunodominant allergen P34/Gly m Bd 30k

Soybean [Glycine max (L.) Merr.] seed contains an immunodominant human allergen P34 or Gly m Bd 30k (mentioned as P34) of the cysteine protease family. Of approximately 16266 accessions from USDA soybean germplasm screened, 12 P34 null lines were identified among soybean (G. max), wild annual (Glycine soja Sieb, and Zucc.), and wild perennial Glycine spp. Glycine soja were low P34 expressers, while G. max and wild perennial species had nondetectable levels of the allergenk protein. Further investigation of G. max nulls by 2D-IEF/SDS PAGE snowed all primary seed proteins present indicating that the loss of P34 was not due to large scale restructuring of protein content. Southern and northern analysis showed no large insertions or deletions to render the gene nonfunctional. The cDNA of both G. max nulls each showed the same six point mutations indicating the two nulls have a single origin. Of these six single nucleotide changes, four are predicted to result in an amino acid alteration. One such alteration results in a serine being replaced by a cysteine residue. The introduction of a cysteine residue might produce a mismatched disulfide bond formation producing an unstable P34 protein in the null soybean accessions. The isolation and introgression of soybean lines with low allergen levels will provide the basis for developing a low allergen line incorporated with other agronomically desirable traits in a breeding program.