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Submitted to: Plant Cell Reports
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/11/2001 Publication Date: 2/1/2002 Citation: KRISHNAN, H.B. EVIDENCE FOR ACCUMULATION OF THE BETA SUBUNIT OF BETA CONGLYCININ IN SOYBEAN (GLYCINE MAX [L.] MERR.) EMBRYONIC AXES. PLANT CELL REPORTS. 2002. V. 20(9). P. 869-875. Interpretive Summary: Soybean is a rich source of protein. Unfortunately, soybean proteins contain low amounts of two important amino acids, methionine and cysteine, that are vital for optimal growth of humans and animals. Therefore, attempts are being made to increase the amount of these two amino acids in soybean proteins. This study reports the occurrence of proteins that are poor in methionine and cysteine in the embryonic axis of soybean seeds. This poor quality soy protein occurs in considerably lower amounts in the axes as compared to the cotyledons. Understanding how two different organs regulate the accumulation of sulfur-poor beta conglycinin will provide insights into improving the protein quality. The information obtained from this basic study will eventually help biotechnologists to design soybean proteins with superior quality to meet the nutritional requirements of the multitude of malnourished people around the world. Technical Abstract: Sodium dodecyl sulfate polyacrylamide gel electrophoresis of total proteins from soybean cotyledons and embryonic axes revealed similar storage proteins in both organs. Results from Western blot analysis using antibodies raised against the purified beta-subunit of beta-conglycinin demonstrated accumulation of the beta-subunit in embryonic axes. This accumulation followed a temporal pattern similar to that of cotyledons. Axis beta-conglycinin was broken down during the initial stage(s) of seed germination, and was completely mobilized within 3 days after imbibition. Subcellular fractions were isolated from developing embryonic axes using metrizamide density gradients and were analyzed by Western blots. Storage proteins were enriched in lighter fractions of the gradient, along with immunoglobulin heavy-chain binding protein. Electron microscopy of the storage-protein-enriched gradient fraction revealed small vesicles and protein aggregates. Protein A-gold immunocytochemistry was used to localize the occurrence of the beta-subunit of beta-conglycinin within the protein aggregates present in the metrizamide gradient, and in the protein bodies present in mature embryonic axes. |
