Critical Plant Gene Takes Unexpected Detour That Could Boost Biofuel Yields

by Sara Shoemaker (Oak Ridge National Laboratory/Phys.org) For decades, biologists have believed a key enzyme in plants had one function—produce amino acids, which are vital to plant survival and also essential to human diets.

But for Wellington Muchero, Meng Xie and their colleagues, this enzyme does more than advertised. They had run a series of experiments on poplar plants that consistently revealed mutations in a structure of the life-sustaining enzyme that was not previously known to exist.

Their discovery could alter the course of gene functional studies in plants and, if applied, it could squeeze more potential out of poplar as a renewable resource for making biofuels and bioproducts.

"At first, we thought it was a mistake, because the enzyme does not need to bind DNA to perform its known function," said Muchero, a biologist at the Department of Energy's Oak Ridge National Laboratory. "We repeated the experiment multiple times and kept seeing evidence in the data that the same gene involved in making amino acids also regulates the function of genes involved in producing lignin."

"This regulation is happening at a higher level in the plant's overall biological system," he added.

They found that poplar plants with certain mutations created unexpectedly low levels of lignin across different environments and tree ages.

Less lignin makes plants easier to breakdown during the industrial poplar-to-biofuels process.

"This enzyme's unique behavior contrasts with conventional wisdom in the plant community," Muchero said. "While we do not know how this new function came about in poplar, we now know that this enzyme exhibits the same behavior in other plant species."

The new insights will help support ORNL industry partners GreenWood Resources and Forage Genetics International who have licensed the poplar gene technology for separate applications, but each with the common goal of breeding plants with modified lignin content.