New Method Improves Transgene-Free Plant Genome Editing
A study in *Nature Plants* demonstrates a high-efficiency method for transgene-free plant genome editing. The technique uses viral delivery of an engineered TnpB, a CRISPR-related enzyme, bypassing labor-intensive tissue culture and offering a more scalable approach for crop improvement.
- The push for "transgene-free" methods addresses both regulatory hurdles and public perception concerns surrounding genetically modified organisms (GMOs), as foreign DNA integration is often what subjects edited crops to strict regulation. - Traditional plant genome editing frequently relies on *Agrobacterium*-mediated transformation, a method that can be time-consuming and is not effective for all crop species, particularly important ones like citrus and apple. - The TnpB enzyme is significantly smaller than the more commonly known Cas9 enzyme, comprising only about 400 amino acids compared to Cas9's 1300. This compact size makes it a much better cargo for viral delivery systems, which have limitations on the amount of genetic material they can carry. - TnpB is the evolutionary ancestor of the Cas12 family of CRISPR enzymes and functions as an RNA-guided nuclease, using a guide RNA to find its target DNA sequence, similar to CRISPR-Cas systems. Researchers in computational biology and bioinformatics model and engineer such enzymes to improve their efficiency; initial versions of naturally occurring TnpB only had a success rate of 3-10% in editing plant genes. - Using a virus, like the Tobacco rattle virus, as a delivery vehicle allows the editing machinery to be introduced into plant cells without integrating into the plant's genome. This avoids the lengthy process of breeding subsequent generations to remove the foreign genes, which is especially difficult in slow-growing perennial plants. - A career in biotechnology product development could involve optimizing this viral vector system for different crops, a task that has been a significant barrier for using CRISPR in many major agricultural plants. For example, researchers at UC Davis have worked on engineering viral vectors to ensure the genetic edits are heritable by being passed down through the plant's seeds. - Professionals in plant biotechnology apply these tools to create specific, valuable traits. For instance, genome editing has been used to develop wheat resistant to fungal diseases like powdery mildew, and to increase the grain yield of rice by 25-31% in field tests.
