By Doug Schmitz
AMES, Iowa – A new Iowa State University (ISU) project supported by a USDA grant will explore the potential to employ viruses to overcome the usual tissue culture barriers that impede plant gene editing in sorghum and switchgrass.
“We believe we can develop this new tool to simplify and accelerate gene editing applications in sorghum and switchgrass, which will enable more rapid progress in improving agricultural traits related to yield, stress and disease resistance and nutrient use efficiency,” said Steve Whitham, an ISU professor of plant pathology and microbiology, who will lead the project.
Funded by the USDA Agriculture and Food Research Initiative, the two-year, $300,000 grant is part of a $3.4 million multi-institution investment in 12 projects nationwide that are part of a USDA Ag Innovation through Gene Editing Initiative.
Co-investigators Maria Salas-Fernandez, ISU associate professor in agronomy, and Shuizhang Fei, ISU professor of horticulture, will also be involved in the research.
The researchers plan to use plant viruses, such as Foxtail mosaic virus, as vehicles for delivering guide RNAs in sorghum and switchgrass. The guide RNAs are part of CRISPR gene editing systems that can direct changes in genetic sequences to modify the functions of genes, Whitham said.
The overall goal of the project is to create controlled techniques to introduce the guide RNA from compatible plant viruses into cells of the target plants, inducing desirable gene edits that can be inherited.
Whitham said sorghum is important for grain and forage production, and both sorghum and switchgrass are important feedstocks for bioenergy production due to their ability to fix large amounts of carbon and convert it into biomass.
“Both species can be transformed by Agrobacterium, but the process is challenging and genotype-dependent, and thus, the full potential of genome editing cannot yet be fully realized,” he said. “Viruses are natural gene delivery vehicles that are used to express proteins and non-coding sequences in plants as they grow and develop, and are thus suitable for delivering gene editing reagents.”
Sorghum and switchgrass can be transformed by traditional gene-editing technologies, but successful transformation is restricted to only certain genotypes and the process is lengthy.
As a perennial crop, Fei said switchgrass is an especially time-consuming plant to breed using conventional technologies. He said he foresees the research being used to enhance traits such as delayed flowering or increased tillering for more stems per plant, which could increase yields and improve economics for producers.
Salas-Fernandez said sorghum is one of the most difficult crops to transform through conventional practices. “It is a big bottleneck for breeding,” she said. “If we can succeed at this, heritable edits can be transferred to the next generation, which would avoid a lot of steps in what is now a very long process, and make sorghum more competitive as a biofuel.”
Whitham emphasized the ‘proof of concept’ nature of the new grant.
“This support is for technology development to see if it can work. We’re optimistic and have a good start, but we have a lot of work ahead to develop and demonstrate this as a practical tool.”