This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: 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 are published in Nature Communications.
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 versions 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 Mandadi, 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." 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. 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, an AgriLife Research associate research scientist at the Texas A&M AgriLife center at Weslaco, is the primary author of the 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.
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