Submitted to: International Association for Plant Tissue Culture & Biotechnology Congress
Publication Type: Abstract Only
Publication Acceptance Date: 6/23/2002
Publication Date: N/A
Technical Abstract: Soybean (Glycine max [L.] Merr.) is a rich source of protein for livestock and humans. However, the nutritional quality of soybean proteins is not optimal due to a deficiency in sulfur-containing amino acids. One-way to overcome this problem is by expressing heterologous proteins in soybean that are extremely rich in sulfur-containing amino acids. Brazil nut 2S albumin, maize delta-zeins, and synthetic proteins rich in methionine and lysine have been expressed in transgenic crops with varying amounts of success. We are interested in expressing high-methionine delta-zeins in soybeans to elevate the methionine content of soybean seeds. As a first step in this direction, we have isolated genes encoding the delta-zeins. In addition to the previously identified 10 and 18 kD delta-zeins, we identified a novel 11 kD methionine-rich delta-zein from developing endosperm of the W23a1 maize inbred line. The nucleotide sequence of this new delta-zein is identical to the published 10 kD delta-zein except for an insertion of 18 nucleotides between +316 and +333 bp from the translation start site. The 11 kD zein contains 21% methionine. Northern blot analysis revealed temporal differences in the RNA transcript levels of the 11 kD and 18 kD delta-zeins between B73 and W23a1 maize inbred lines. Western blot analysis using antibodies raised against the purified 11 kD zein showed gradual accumulation of this protein throughout the seed development. Electron microscopic immunocytochemistry indicated that the 11 kD delta-zein was primarily localized on the outer regions of the protein bodies. Experiments are in progress to express this novel methionine-rich protein in transgenic crops.