A University of Connecticut researcher recently made advancements in citrus gene editing techniques to reduce the drawbacks of traditional methods. The researcher is Yi Li, professor of horticultural plant breeding biotechnology in the College of Agriculture, Health and Natural Resources.
BACKGROUND
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.
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 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 approach can be applied to most crop species for the rapid production of non-GMO, genome-edited plants.
The 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 crops, providing 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.
RECENT REFINEMENT
Li’s lab and collaborators have further refined this method to achieve higher efficiency using citrus plants as a model system. Their latest findings were published in Horticulture Research.
A promising approach to combat the HLB disease that has devastated Florida citrus 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 the researchers’ 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.
Source: University of Connecticut
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