Moving Gene In Plant Results In Increased Production Of Amino Acid.

2001 OCT 17 - (NewsRx.com & NewsRx.net) -- By placing a nuclear gene in another location - its original home in a plant - researchers have successfully enhanced the production of an essential amino acid.

The work suggests that alterations of biosynthetic pathways could guide plants to produce more of a desired dietary component. In this case, tobacco produced 10 times its usual amount of tryptophan - an amino acid often in short supply in the human diet and vital for the production of serotonin in the brain.

Scientists inserted the gene, known to produce the control enzyme involved in tryptophan production, into the chloroplast genome. Chloroplasts are the chlorophyll containing plastids where photosynthesis occurs. The approach essentially is a reversal of evolution.

"The biosynthesis of tryptophan and other essential amino acids occurs in these plastids," said Archie R. Portis Jr., a University of Illinois crop scientist and researcher in the USDA-Agricultural Research Service Photosynthesis Research Unit at the UI in the article published in the September 2001 issue of Plant Physiology. "However, the genes encoding these enzymes are located in the nucleus and the proteins are imported into the plastids."

Plastids in today's plants are believed to have evolved some two billion years ago from a unicellular, photosynthetic cyanobacteria containing its own set of genes that was engulfed by nonphotosynthetic cells.

"Most of the genes originally located in these early plastids moved to the nucleus," Portis said. "It is likely that those required for tryptophan biosynthesis were among these."

The gene the ...