Switchgrass (Panicum virgatum L.) is a high yielding perennial grass species
that is considered as a model biomass crop. However, the self-infertility
and high ploidy level of this species make it difficult to study gene
function or improve germplasm. Iowa State University's Yang Liu explored the
feasibility of using CRISPR-Cas9 for targeted mutagenesis in tetraploid
The team first tested CRISPR in switchgrass with a non-functional
green-fluorescent protein gene with an insertion in its 5$B!l(B coding region.
The gene was successfully mutated by a Cas9/sgRNA complex, resulting in its
restored function. Agrobacterium-mediated transformation of calli derived
from mature caryopses was then performed, targeting several genes, namely
teosinte branched 1 (tb1) a and b and phosphoglycerate mutase (PGM).
Primary transformants (T0) containing CRISPR-Cas9-induced mutations were
obtained at frequencies of 95.5% (tb1a) and 11% (tb1b), with the T0 mutants
exhibiting increased tiller production. Meanwhile, a mutation frequency of
13.7% was also obtained for the PGM gene. No apparent phenotypical
alterations were observed in the PGM T0 mutants.
This study proves that CRISPR-Cas9 system can generate targeted mutagenesis
effectively in switchgrass.