According to a group of Belgian researchers, today's fossil-based economy results in a net increase of CO2 in the Earth's atmosphere and is a major cause of global climate change. They seek to counter this.
Led by Professor Wout Boerjan at Belgium's Flanders Institute of Biotechnology, a research team has discovered a way to stably finetune the amount of lignin in poplar by applying CRISPR/Cas9 technology. CRISPR is a technology capable of isolating and editing specific genes inside a cell.
Lignin is one of the main structural substances in plants and it makes processing wood into, for example, paper difficult. Woody biomass can play a crucial role in such a bio-based economy by serving as a renewable and carbon-neutral resource for the production of many chemicals. Unfortunately, the presence of lignin hinders the processing of wood into bio-based products.
"A few years ago, we performed a field trial with poplars that were engineered to make wood containing less lignin," says Boerjan. "Most plants showed large improvements in processing efficiency for many possible applications. The downside, however, was that the reduction in lignin accomplished with the technology we used then - RNA interference - was unstable and the trees grew less tall."
Undeterred, the researchers went looking for a solution. They employed the recent CRISPR/Cas9 technology in poplar to lower the lignin amount in a stable way, without causing a biomass yield penalty. In other words, the trees grew just as well and as tall as those without genetic changes.
"Poplar is a diploid species, meaning every gene is present in two copies," said Barbara De Meester, another researcher. "Using CRISPR/Cas9, we introduced specific changes in both copies of a gene that is crucial for the biosynthesis of lignin. We inactivated one copy of the gene, and only partially inactivated the other. The resulting poplar line had a stable 10% reduction in lignin amount while it grew normally in the greenhouse. Wood from the engineered trees had an up to 41% increase in processing efficiency".
"The mutations that we have introduced through CRISPR/Cas9 are similar to those that spontaneously arise in nature," says Dr. Ruben Vanholme. "The advantage of the CRISPR/Cas9 method is that the beneficial mutations can be directly introduced into the DNA of highly productive tree varieties in only a fraction of the time it would take by a classical breeding strategy."
The applications of this method are not only restricted to lignin but might also be useful to engineer other traits in crops, providing a versatile new breeding tool to improve agricultural productivity, the team says.
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