- by Gabe Saldana
Editing a plant's genes is only half the battle. Before a new, improved trait can ever reach a farmer's field, scientists must be able to grow a whole plant from just a few edited cells — a process that can be slow, unreliable and, for some plant species, impossible.
A new study led by researchers at Texas A&M AgriLife Research , the University of Maryland and the U.S. Department of Agriculture , USDA, describes a way to speed up that bottleneck across crops, including perennials such as citrus, strawberry, poplar and potatoes. The findings were published in Nature Communications .
Kranthi K. Mandadi, Ph.D., led research that contributed to speeding up a process for growing gene edited plants from cells. (Sam Craft/Texas A&M AgriLife)
The team developed a system called CRISPR-Combo, which allows scientists to edit a gene of interest and simultaneously activate the plant's own natural "morphogenic" genes. These control how cells divide and develop into roots, shoots and eventually entire plants. Instead of inserting extra copies of these growth-promoting genes, CRISPR-Combo turns up the plant's own version of these genes where they already sit in the genome, using the same CRISPR tool that makes the gene edit.
"Regeneration is one of the biggest roadblocks standing between a promising gene edit in the lab and a crop variety that's actually useful to growers," said Kranthi Mandadi, Ph.D., director of the Texas A&M AgriLife Research and Extension Center at Weslaco and professor in the Texas A&M Department of Plant Pathology and Microbiology . "This work shows that we can coax a plant's own genes to regenerate faster and more reliably, and that approach holds real promise for perennial crops like citrus that have historically been very difficult to work with in the lab."
Why it matters for growers
Perennial crops such as citrus and poplar can take years to move through a single breeding cycle, and many high-value fruit and nut crops have proven especially resistant to laboratory transformation and regeneration.
By activating a plant's own regeneration genes rather than relying on added hormones or extra genetic material, CRISPR-Combo offers a more streamlined, scalable approach. The team believes this approach can be adapted to screen for morphogenic genes in other commercially important crops that respond poorly to typical regeneration methods.
Screening dozens of genes, crop by crop
To determine which genes were worth activating, the team first screened candidates using a fast, high-throughput "hairy root" system developed by AgriLife Research. The system induces root growth on plant cuttings without the lengthy process of regenerating a full plant.
Manikandan Ramasamy, Ph.D., AgriLife Research associate research scientist at the Texas A&M AgriLife center at Weslaco, is the primary author of the published study.
"In potatoes, we screened 17 candidate genes and identified four that boosted hairy root production," Ramasamy said. "Three of those also improved shoot regeneration when tested, raising regeneration efficiency to 45%-70%, compared with about 30%-35% in controls."
In citrus, a crop notoriously resistant to transformation and regeneration, the team screened 10 candidate genes and found five that meaningfully boosted hairy root formation. In lab conditions, all five pushed shoot regeneration efficiency to 80% or higher, compared with under 60% in controls.
Stacking genes cuts regeneration time by a month or more
In wild strawberry and poplar, the researchers went a step further, activating two morphogenic genes at once rather than just one. Simultaneously activating certain genes in strawberries shortened the time needed to produce a fully regenerated, gene-edited plant by more than a month compared with standard methods.
In poplar, co-activating genes produced an even bigger shift: shoots regenerated in less than a month, and — notably — did so without adding any external plant hormones, which are normally required in tissue culture. The poplar lines with both genes activated showed the highest rates of edited cells and grew into taller, higher-biomass plants in the greenhouse, with no obvious abnormalities.
The research was supported primarily by the Foundation for Food and Agriculture Research's Genotype-Independent Regeneration of Fertile Plants program, with additional support from the U.S. National Science Foundation , USDA National Institute of Food and Agriculture , the U.S. Department of Energy , Texas A&M AgriLife Institute for Advancing Health Through Agriculture and AgriLife Research's Insect Vector Disease program.
