Plant phenylalanine yield increase encounters bottleneck

Scientists Natalia Dudareva and Joseph Lynch of Purdue University in the United States are devoted to studying methods to increase plant phenylalanine production. Phenylalanine is essential for the survival of plants and is used in flavors, fragrances, biofuels, pesticides and medicines.

 
They discovered a new plant metabolic pathway last year. They thought it could be genetically modified to allow plants to produce more phenylalanine.

 
Genetic modification should have increased the production of phenylalanine, but as a result, the compound unexpectedly decreased. However, this shows that there is a link between the biosynthesis of phenylalanine and the phytohormone auxin, which not only affects the metabolism of amino acids, but also affects our understanding of growth and development.

 
Plants use phenylalanine to produce compounds to attract pollinators for defense, reproduction, growth and development. Although sufficient for these purposes, it is too small for human use.

 
Plants mainly produce phenylalanine in plastids, such as chloroplasts and other small organelles. But Purdue University research scientist Du Dareva and graduate student Yichun Qian found that plants can also produce phenylalanine in the cytoplasm and may produce more.

 
Scientists first let petunia grow to maturity and then induce an enzyme that can increase the production of phenylalanine in the cytosol.

 
"The effect is very good, the synthesis of phenylalanine has tripled." Lynch said.

 
Then they integrated a gene into the petunia genome, which would increase the production of the same enzyme and should produce similar results.

 
In contrast, the production of phenylalanine increased slightly in the cytosol, but decreased significantly in the plastid. This resulted in an overall reduction in phenylalanine production.

 
This is because both phenylalanine and auxin use a substrate called phenylpyruvate for biosynthesis. By producing more phenylalanine in the cytosol, phenylpyruvate in this area is increased, resulting in more auxin production.

 
Slight changes in plant hormones can cause serious developmental problems. In the above situation, auxin increased, resulting in a decrease in plastids, and phenylalanine production decreased accordingly. "Increasing phenylalanine will not work, because it will interfere with auxin, and we have entered a dead end." Lynch said.

 
"We will continue to try to increase the production of phenylalanine, but we will try to overcome the bottleneck of limited production in this region by adjusting the plastid.

 
Dudareva said that the above findings not only show how phenylalanine and auxin are related, but also suggest why plants have a less-used cytosol channel.


Plants can produce enough phenylalanine through tight plastid channels through the regulation mechanism, but will not produce more to prevent breaking the balance with auxin. But when a plant is injured or needs more phenylalanine for defense or healing, it will open the cytosol channel and produce the required amount.