Breeding for Specific Amino Acids
The demonstration that single-gene substitutions can result in marked increases in the content of the limiting essential amino acids for nutrition of humans or monogastric animals has been made for maize (6,12) and barley (9). It is then naturally a question of the extent of our ability to manipulate the amino acid content of economically important plants. Could one enhance the content of any desired amino acid in any plant tissue? The answer to this question clearly is negative, and the reasons for so concluding are the subject of this chapter. They constitute an essential background for any investigator interested in the improvement of plant protein quality. Understanding the severe restrictions on the system allows a reasonable estimation of the probability of success. The restrictions to which I refer take this form: The primary sequence (the order of amino acids) of a polypeptide chain is specified by the structural gene for that polypeptide in the DNA codescript. Decoding takes place through transcription into an RNA intermediate and translation into a polypeptide chain via ribosome-based protein synthesis. Because the sequence is specified, polypeptide chains synthesized on the same RNA message are identical, barring the occurrence of relatively infrequent mistakes in translation.
KeywordsAmino Acid Composition Lysine Content Monogastric Animal High Lysine Endosperm Protein
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