'Our new but simple method is far more effective and can now be applied to a much wider range of plant species than our original approach'
Yi Li of the Department of Plant Science and Landscape Architecture in the College of Agriculture, Health and Natural Resources works with students on turfgrass research projects in a greenhouse on the Depot campus. July 6, 2023. (Jason Sheldon/UConn Photo)
Genetically modified organisms, also known as GMOs, have been a hot topic of conversation amongst researchers, producers, government agencies, and the general public for decades.
GMOs are banned in some countries and highly regulated in most, but they have benefits too: they have provided a way to grow plants better, faster, and more sustainably for growing populations around the globe.
Yi Li, professor of horticultural plant breeding biotechnology in the College of Agriculture, Health and Natural Resources (CAHNR), has made advancements in gene editing techniques to reduce the drawbacks of traditional methods.
Scientists employ genome-editing technologies to precisely modify a plant's own genes, either by inactivating or activating specific target genes without introducing foreign DNA. This strategy enables the development of plants with desirable traits, such as improved drought and heat tolerance.
However, to perform genome editing, scientists must first introduce CRISPR and other related genes - foreign DNA sequences - into the plant cells. As a result, even though the plant's own genes are being edited and the changes lead to desirable traits, these genome-edited plants are still considered genetically modified organisms (GMOs) because they contain foreign genes and proteins like Cas9.
This process creates transgenic plants, more commonly known as genetically modified organisms (GMOs), which may be banned or highly regulated in many countries.
This regulation can often be a deterrent to industry and small producers. Since the deregulation process is long and expensive, industries may not have an incentive to develop transgene-free genetically modified plants.
In 2018, Li's research team developed a novel method to create transgene-free, genome-edited plants to address this challenge. This simple approach can be applied to most crop species for the rapid production of non-GMO, genome-edited plants. It is particularly useful for perennial crops that are vegetatively propagated or require several years to produce seeds.
The principle of their method is based on Agrobacterium-mediated transient expression of CRISPR and other genes, allowing genome editing to occur without integrating any foreign genes into the plant's genome. This technique has been widely adopted in various crop species, providing a powerful tool for the rapid generation of non-GMO, genome-edited plants.
Although several transgene-free gene editing methods exist, most are technically demanding or time-consuming. Li's approach offers an efficient and practical alternative.
Li's lab and collaborators have further refined this method to achieve higher efficiency using citrus plants as a model system. These latest findings were published in Horticulture Research, a leading scientific journal in plant science.
Citrus is a major U.S. agricultural industry that is currently facing a severe threat from Huanglongbing, a devastating disease that has destroyed about 70% of citrus trees in Florida. One promising approach to combat this disease is to develop genome-edited citrus plants with natural immunity to the pathogen.
The main innovation described in Li's paper was the use of kanamycin, a chemical that helps identify cells temporarily or stably expressing CRISPR-related genes in Agrobacterium-infected plant cells for only three to four days during the genome-editing process.
Because resistance to kanamycin is linked to the expression of CRISPR genes, this short treatment helped prevent cells that were not infected by Agrobacterium from growing. As a result, the successfully edited cells were able to grow into plants more efficiently, without being crowded out by unedited cells.
The new method was 17 times more efficient than their 2018 version in producing genome-edited citrus plants.
"Our new but simple method is far more effective and can now be applied to a much wider range of plant species than our original approach," Li says.
This work relates to CAHNR's Strategic Vision area focused on Ensuring a Vibrant and Sustainable Agricultural Industry and Food Supply.
