IDENTIFICATION OF BIOTINYLATED PROTEINS IN SOYBEAN [GLYCINE-MAX (L.) MERRILL] SEEDS AND THEIR CHARACTERIZATION DURING GERMINATION AND SEEDLING GROWTH

Biotin is an important vitamin. It is biologically active as a protein prosthetic group, where it functions in enzymatically catalysed carbo xylation reactions. It has previously been shown that the ability to s ynthesize biotin is not necessary for germination of Arabidopsis thali ana seeds, but that this process is required for early seedling growth . This research was conducted to determine if changes in the detection of biotinylated proteins could be observed that reflect changes in th e need for biotin-mediated enzyme reactions observed during early soyb ean seedling growth. A seed specific 75-kDa biotinylated protein prese nt in the embryonic axes and the cotyledons was lost during the first 3 d of germination. Seed specificity, and pattern of expression during germination suggest that this protein is a homologue of the seed spec ific 65-kDa biotinylated protein previously identified in pea (Pisum s ativum). If samples were not treated with 2-mercaptoethanol, three equ ally spaced proteins at approx. 85 kDa were visible. In the presence o f 2-ME these proteins appeared as a single 85-kDa band. This triplet w as distinct only in the embryonic axes of dry seeds and not in imbibed seeds or in other plant parts. This demonstrates that imbibitional ch anges do occur in the pool of biotinylated proteins present in dry soy bean seeds, and that 2-ME treatment can inhibit complete identificatio n of the biotinylated proteins present in seed tissues.