The CRISPR-Cas9 gene-editing technology is one of the most important scientific breakthroughs of recent decades, but there is always room for improvement. Researchers at the University of Maryland (UMD) have developed a system they call CRISPR-combo, which can edit multiple genes at once while also changing the expression of others in plants.
The CRISPR system is a powerful tool, allowing scientists to cut and paste specific genes into living organisms. This opened up the possibility of new treatments for a wide range of diseases, including cancer, diabetes, genetic forms of blindness, and blood diseases. Edits can also be made to improve crops and farm animals, enable new forms of pest control, and create useful new types of microbes.
Later developments improved upon the CRISPR recipe. Some allowed many different genes to be edited at the same time, while other versions avoided cutting the DNA altogether, instead focusing on turning gene expression on or off as needed.
In the new study, the UMD researchers combined both of these techniques into one tool, aptly called CRISPR-Combo. Typically, a guide RNA strand performs either an editing or activation function, meaning that they can only perform one or the other. For this study the team assigned two functions to different RNAs – editing to the common Cas9, and activation to a scaffolding sgRNA.
The team tested the concept in several experiments. First, they used tomato and rice plants to demonstrate that they could perform both functions without any crossover – and the tests were successful.
Co-author Yiping Qi said, “As a proof of concept, we showed that we can eliminate gene A and successfully cross-react or activate gene B, without accidentally crossing over gene B.” or upregulate gene A.” Study.
Next, he experimented with a common laboratory plant called Rockcress to see how the two beneficial changes could be made simultaneously. They edited a gene that makes plants more resistant to herbicides, and activated a gene that makes the plants flower early. The end result is an engineered rockcress that is both herbicide-resistant and reproduces twice as rapidly, yielding eight generations in a single year.
Left: poplar plants grown with single gene editing using regular CRISPR-Cas9. Right: Poplar grown using the new CRISPR-combo to edit one gene and activate the other
University of Maryland
In other tests, the team set out to improve the efficiency of breeding new varieties of plants through tissue cultivation. They edited useful genes in poplar and activated three others that promote tissue regeneration in plants, and found that new roots grew much faster in poplar samples, improving the success rates of engineered crops.
Meanwhile, rice plants edited using CRISPR-combo were found to grow from cultures without the need for normal growth hormone supplements, and expressed more edited genes than those grown with the hormone.
The team says the new technology opens up a wider range of possibilities in editing crops and other plants more efficiently, providing them with properties such as herbicide resistance and enhanced nutrition.
“The possibilities are really limitless in terms of traits that can be combined,” said study co-author Yiping Qi, an associate professor in the Department of Plant Science and Landscape Architecture. “But what’s really exciting is that CRISPR-Combo introduces a sophisticated level of technology to genetic engineering in plants that we didn’t have before.”
The research was published in the journal Nature plants.
Source: University of Maryland
