Isolation of peanut genes encoding arachins and conglutins by expressed sequence tags

Seed storage proteins commonly comprise various groups of multiple isoforms encoded by different gene families. Arachin (11S globulin), conarachin (7S globulin) and conglutin (albumin) are the three major storage proteins in peanut (Arachis hypogaea L.). In order to isolate peanut seed storage protein genes, we sequenced and analyzed more than 400 randomly selected clones from a cDNA library derived from mid-maturation stage cotyledons of peanut. Our analysis indicated that arachin isoform precursors were encoded by at least five genes, whereas conglutins were encoded by more than six genes. The full-length cDNAs that encode isoforms of five arachin and six conglutin precursors were obtained. Among these cDNA clones, the deduced polypeptide of Ara 1 has about 99% similarity to that of peanut allergen Ara h 3. In addition, the deduced amino acid sequences of three conglutins, AhCONG 1, AhCONG 2 and AhCONG 5, are identical to those of peanut allergens Ara h 2.02, Ara h 2 and Ara h 6, respectively. Our study identified four new members (Ara 2 to Ara 5) of arachin family and two new members (AhCONG 3 and AhCONG 6) of conglutin family in peanut.