Researchers Demonstrate First Precision Gene Editing in Miscanthus

The Science

Adaptable and easy to grow, miscanthus (or silvergrass) shows great potential as a sustainable bioenergy crop. This productive perennial grass can thrive on marginal lands and requires limited fertilization. It also has high tolerance for drought and cool temperatures, and it uses an efficient form of photosynthesis. Previous efforts to genetically improve miscanthus focused on transforming plants by introducing external genes at random places in their genomes. In this study, researchers developed gene-editing procedures using CRISPR/Cas9. This will allow scientists to selectively target existing genes to knock out, or modify, their function and introduce new genes into precise locations. That targeting ability offers a new avenue for developing improved varieties with enhanced speed and specificity.

The Impact

Precision gene-editing will allow scientists to tap the huge potential of this highly productive but genetically complex grass. Miscanthus shows promise as a source for biofuels, renewable bioproducts, and carbon sequestration. Ultimately, it could help reduce reliance on petroleum-based energy. This would enhance the broader efforts to develop sustainable bioenergy production and to engineer select crops to produce novel bioproducts, such as oils and high-value chemicals. This new research expands scientists’ ability to precisely edit miscanthus to enhance productivity, grow on marginal lands, and produce specialty chemicals. This will help realize its status as a viable bioenergy crop.

Summary

The Center for Advanced Bioenergy and Bioproducts Innovation (CABBI) team demonstrated gene editing in three species of miscanthus — the highly productive Miscanthus x giganteus, which is grown commercially for bioenergy, and its parents, M. sacchariflorus and M. sinensis. Because those plants are paleo-polyploids, with duplicated ancient sorghum-like DNA and multiple sets of chromosomes, the design of the guide RNAs that locate genetic material for editing needed to target all copies of a gene to account for redundancy and ensure a full “knock out” of a gene’s function.

The CABBI researchers built on similar gene editing in Zea mays (maize), which identified the lemon white 1 (lw1) gene as a helpful target for visual confirmation of genetic changes. That gene is involved in chlorophyll and carotenoid biosynthesis, which affects leaf color, and prior studies demonstrated that editing lw1 via CRISPR/Cas9 yielded pale green/yellow, striped, or white leaf phenotypes. Using sequence information from both miscanthus and sorghum, researchers identified guide RNAs that could target homeologs, or duplicated gene copies, of lw1 in miscanthus plant tissue. The leaves on the edited miscanthus plants displayed the same phenotypes found in maize, with pale green/yellow, striped, or white leaves instead of the typical green.

Funding

This research was funded by the Department of Energy (DOE) Center for Advanced Bioenergy and Bioproducts Innovation under an award from the DOE Office of Science, Office of Biological and Environmental Research.