Lignin, a major component of the plant cell wall, stands as a barrier to
efficient biofuel production from switchgrass (Panicum virgatum). While the
advent of genome editing technologies offers new opportunities for improving
switchgrass, its allotetraploidy (2n = 4x =36) may make it difficult to
engineer.

The team of Jong-Jin Park of Oak Ridge National Laboratory developed a
CRISPR-Cas9 genome editing system in switchgrass to target
4-Coumarate:coenzyme A ligase (4CL), a key enzyme involved in the early
steps of the synthesis of monolignol, a component of lignin. Among the three
4CL genes identified in switchgrass, the Pv4CL1 transcripts were the most
abundant.

Pv4CL1 was then selected as the target for CRISPR-Cas9 editing and a guide
RNA was constructed to target it. Among the 39 genome-edited plants were
generated, four plants were confirmed to have tetra-allelic mutations
simultaneously. The Pv4CL1 knock-out plants had reduced cell wall thickness,
a significant reduction in total lignin content, an increase in glucose
release as well as an increase in xylose release.

This study established a success of CRISPR-Cas9 system in switchgrass. The
system will be useful for decreasing the lignin content of lignocellulosic
feedstock.

[biotechnologyforbiofuels.biomedcentral.com]
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