Tomatoes are big business. In the U.S. alone, farmers sell about $2 billion worth of this popular fruit. But the tomato is also an important model species—especially at BTI—which researchers use to study fruit ripening and nutrition. Last year, Assistant Professor Joyce Van Eck, along with colleagues from Cold Spring Harbor Laboratory in New York and Sainsbury Laboratory in the United Kingdom successfully adapted a new genome editing technology for their studies of this important crop.
In a study that appeared in the November 2014 issue of Plant Physiology, Van Eck and her colleagues show that the technology called CRISPR/Cas9 can edit the tomato genome with relative ease and precision. This technology could potentially be used to create improved crop varieties. Scientists have used this gene editing tool in multiple species, including bacteria, soybeans, mice and monkeys. However, to Van Eck’s knowledge, this study is the first published use of the technology to create a modified tomato plant.
The ease of use of the CRISPR/Cas9 system suggests that it may become the “technology of choice” to alter DNA for genetic studies. The tomato makes an excellent target for CRISPR/Cas9 editing because its genome has just two copies of each gene and because experiments can be planned using the high-quality tomato genome sequence.
The editing technique uses an enzyme called Cas9 that can snip through double-stranded DNA. The CRISPR contains a carefully designed guide RNA sequence that leads the Cas9 to the section of the genome to be edited. Enzymes within the cell then repair the cuts created by Cas9, often adding or removing bases, which can render the gene inactive. By deactivating specific genes, researchers can better understand which ones determine characteristics such as taste, productivity or insect resistance.
To test out the technique in tomatoes, Van Eck and colleagues decided to make mutations in a gene that create plants with an easily identifiable “wiry” appearance, called SlAGO7. The CRISPR/Cas9 system successfully created several mutations that cause long, skinny plants. Though the SlAGO7 mutations cause limited fertility, the researchers showed that the plants passed on the mutations to their progeny, indicating that they had made a new variety.
For Van Eck, the research is the first step of an NSF-funded project to identify genes that could increase yield in tomatoes and other crops.