Location: Market Quality and Handling Research
Title: Comparative Proteomic Analysis of Peanut Seed and Seed Coat Authors
Submitted to: American Peanut Research and Education Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: March 29, 2013
Publication Date: N/A
Technical Abstract: Peanut (Arachis hypogaea L.) is grown extensively worldwide for its edible seed and oil. In a peanut, within the hull and encasing the cotyledon is the seed coat, which is commonly referred to within the peanut industry as the skin. The seed coat is a distinct plant structure critical for seed development, regulation of nutrient uptake, and defense against various environmental stresses such as fungal invasion. Recently, proteomics has become a powerful tool in plant research; however, studies involving legumes, and especially peanuts, are in their infancy. Furthermore, protein expression in the peanut seed coat has never been explored. Accordingly, a comparative proteomic study of blanched peanut seed and corresponding seed coats was performed using nanoLC-MS/MS sequencing. A phenol-based extraction procedure was necessary to extract seed coat proteins, as seed coats are naturally high in polyphenolic compounds that readily bind and precipitate proteins. Seed coats contained many known peanut allergens (Ara h 1-11) in addition to 38 proteins not identified in the seed, which included several defense proteins with antifungal activity. Western blotting using sera of peanut allergic patients revealed that seed coat proteins bound peanut-specific IgE when isolated from polyphenolic compounds, but not when these compounds were present. These findings have important implications for the potential allergenicity and food uses of peanut skins (processing by-product) and provide a first step towards understanding their biochemical function. Related, research is ongoing to identify proteins in the seed and seed coat that are differentially expressed in response to drought, as this information will aid efforts at developing drought/aflatoxin resistant cultivars. Additionally, proteomics can be used to understand roasting induced protein modifications, information with important implications for allergenicity. To this end, proteins from raw and variably roasted peanuts were compared. Roasted samples contained several proteins with modified lysine residues (carboxyethyllysine, carboxymethyllysine, and pyralline), indicative of Maillard browning. This research demonstrates the utility of proteomics to evaluate protein expression and modifications in peanuts and peanut by-products with important implications for both agronomics and food science.