Submitted to: Plant Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/22/2000
Publication Date: 8/1/2000
Citation: KRISHNAN, H.B., JIANG, G., KRISHNAN, A.H., WIEBOLD, W.J. SEED STORAGE PROTEIN COMPOSITION OF NON-NODULATING SOYBEAN AND ITS INFLUENCE ON PROTEIN QUALITY. PLANT SCIENCE. 2000. v. 157(2). p. 191-199. Interpretive Summary: Soybean is a rich source of protein. Proteins are made up of amino acids. 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 effect of fnitrogen fertilizer application on the quantity and quality of soybean proteins. We found that nitrogen fertilization influenced the amount of some of the soybean seed proteins, leading to changes in the protein quality. This information will help agronomists and biotechnologist to design soybean protein with superior quality to meet the nutritional requirements of the multitudes of malnourished people around the world.
Technical Abstract: A 53 kD protein, which accumulates at low levels in non-nodulating 'Clark' rjirji soybeans, was purified from preparative SDS-PAGE and polyclonal antibodies were raised against the gel-purified 53 kD protein. The N- terminal sequence of the purified 53 kD protein was very similar to the beta-subunit of beta-conglycinin. Western blot analysis using the antibodies raised against the purified beta-subunit of beta-conglycinin revealed that the accumulation of this protein was enhanced in rjirji soybeans when the plants were supplemented with nitrogen. Northern blot analysis indicated that the rjirji soybeans in general had lower abundance of mRNA for the major soybean seed proteins. A one-time application of nitrogen to rjirji soybeans enhanced the accumulation of the 1.6 kB beta- conglycinin beta-subunit mRNA. The 2.1 kB beta-conglycinin alpha'-subunit mRNA levels in the rjirji soybeans were several-fold lower than in RjiRji soybeans, and nitrogen application had no effect on the abundance of this RNA transcript. The amount of RNA encoding an 8.5 kD sulfur-rich protein was two-fold higher in non-nodulating soybeans when compared with nodulated soybeans. Nitrogen application reduced this transcript abundance to levels comparable with that of the nodulated soybeans. Even though rjirji soybeans accumulated less of the beta-subunit of beta-conglycinin, the methionine content of the total seed protein was lower than the nodulated soybeans. However, the rjirji soybeans contained relatively more cysteine than the RjiRji soybeans.