Enhancement of the methionine content of seed proteins by the expression of a chimeric gene encoding a methionine-rich protein in transgenic plants.
We have constructed a chimeric gene encoding a Brazil nut methionine-rich seed protein which contains 18% methionine. This gene has been transferred to tobacco and expressed in the developing seeds. Tobacco seeds are able to process the methionine-rich protein efficiently from a larger precursor polypeptide of 17 kDa to the 9 kDa and 3 kDa subunits of the mature protein, a procedure which involves three proteolytic cleavage steps in the Brazil nut seed. The accumulation of the methionine-rich protein in the seeds of tobacco results in a significant increase (30%) in the levels of the methionine in the seed proteins of the transgenic plants. Our data indicate that the introduction of a chimeric gene encoding a methionine-rich seed protein into crop plants, particularly legumes whose seeds are deficient in the essential sulfur-containing amino acids, represents a feasible method for improving the nutritional quality of seed proteins.
Altenbach
S B
SB
Plant Cell Research Institute, Inc., Dublin, CA 94568.
Pearson
K W
KW
Meeker
G
G
Staraci
L C
LC
Sun
S M
SM
D000596:Amino Acids / Q000032:analysis; D015870:Gene Expression; D005822:Genetic Vectors; D008715:Methionine / Q000235:genetics* / Q000378:metabolism; D009753:Nutritive Value; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010944:Plants / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection
D000596:Amino Acids; D010940:Plant Proteins; D011994:Recombinant Proteins; D008715:Methionine