CRISPR (clustered regularly interspaced short palindromic repeats)-Cas9 in the forest

It seems lignin is a bit of a problem. Its presence in a tree makes processing the wood into various products more difficult. (Of course, some people appreciate trees for other reasons both practical [carbon sequestration?] and/or aesthetic.)

In any event, scientists have been working on ways to reduce the amount of lignin in poplar trees since at least 2014 (see my April 7, 2014 posting titled ‘Good lignin, bad lignin: Florida researchers use plant waste to create lignin nanotubes while researchers in British Columbia develop trees with less lignin’; scroll down about 40% of the way for the ‘less lignin’ story).

(I don’t believe the 2014 research was accomplished with the CRISPR (clustered regularly interspaced short palindromic repeats)-Cas9 technique as it had only been developed in 2012.)

The latest in the quest to reduce the amount of lignin of poplar trees comes from a Belgian/US team, from an Oct. 6, 2020 news item on ScienceDaily,

Researchers led by prof. Wout Boerjan (VIB-UGent [Ghent University] Center for Plant Systems Biology) have discovered a way to stably finetune the amount of lignin in poplar by applying CRISPR/Cas9 technology. Lignin is one of the main structural substances in plants and it makes processing wood into, for example, paper difficult. This study is an important breakthrough in the development of wood resources for the production of paper with a lower carbon footprint, biofuels, and other bio-based materials. Their work, in collaboration with VIVES University College (Roeselare, Belgium) and University of Wisconsin (USA) appears in Nature Communications.

Picture Tailoring lignin and growth by creating CCR2 allelic variants (From left to right: wild type, CCR2(-/-), CCR2(-/*) line 206, CCR2(-/*) line 12) Courtesy: VIB (Flanders Institute of Biotechnology)

An Oct. 6, 2020 VIB (Vlaams Instituut voor Biotechnologie; Flanders Institute of Biotechnology) press release (also on EurekAlert), which originated the news item, explains the reason for this research and how CRISPR (clustered regularly interspaced short palindromic repeats) technology could help realize it,

Towards a bio-based economy

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. To counter this, a shift towards a circular and bio-based economy is essential. 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.

Prof. Wout Boerjan (VIB-UGent): “A few years ago, we performed a field trial with poplars that were engineered to make wood containing less lignin. 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.”

New tools

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.

Dr. Barbara De Meester (VIB-UGent): “Poplar is a diploid species, meaning every gene is present in two copies. 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”.

Dr. Ruben Vanholme (VIB-UGent): “The mutations that we have introduced through CRISPR/Cas9 are similar to those that spontaneously arise in nature. 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.

Here’s a link to and a citation for the paper,

Tailoring poplar lignin without yield penalty by combining a null and haploinsufficient CINNAMOYL-CoA REDUCTASE2 allele by Barbara De Meester, Barbara Madariaga Calderón, Lisanne de Vries, Jacob Pollier, Geert Goeminne, Jan Van Doorsselaere, Mingjie Chen, John Ralph, Ruben Vanholme & Wout Boerjan. Nature Communications volume 11, Article number: 5020 (2020) DOI: Published 06 October 2020

This paper is open access.

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