Using exogenous genes to reduce the set of essential amino acids? Various organisms have sets of essential amino acids that they cannot synthesize themselves, but rather that they must obtain from food. Humans have 9 of these amino acids. However, obviously certain organisms like plants contain the necessary genes to synthesize all of their amino acids. Also, the set of amino acids for various organisms differs. For example, arginine is essential in dogs but not in humans. Have there been any attempts at taking cells from an animal or other organism with essential amino acids and providing them with the necessary genes to synthesize that amino acid, thereby reducing the cell's set of essential amino acids? I am not asking this specifically referring to human cells, nor do I have any particular motivation for asking this other than curiosity.

Decreasing the number of essential amino acids is frequently used as a selection marker during molecular biology experiments: An organism (usually yeast) that cannot synthesize a certain amino acid is first grown in the presence of said amino acid in the media. Then it is transfected with a gene of interest together with the gene that enables it to synthesize the amino acid. Now being grown in a culture medium that does not contain the amino acid, only individuals that were successfully transfected can grow, the others will starve.

A similar approach was also used in Beadle and Tatum's Nobel prize-winning work on the one gene-one enzyme hypothesis.