CRISPRing trees for a climate-friendly economy

A field trial with poplars that were engineered to make wood containing less lignin. Most plants showed large improvements in processing efficiency. However, was that the reduction in lignin accomplished with the technology we used then—RNA interference—was unstable and the trees grew less tall. Then they employed the recent CRISPR/Cas9 technology in poplar to lower the lignin amount in a stable way, without causing a biomass yield penalty.

Poplar is a diploid species - 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 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 were introduced by CRISPR/Cas9 are similar to those that arise naturally. The advantage of the CRISPR/Cas9 method is that the beneficial mutations can be directly introduced into the DNA in only a fraction of the time it used to take.

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.