North Carolina – Researchers from North Carolina State University have achieved a significant breakthrough by transferring a crucial gene from one compartment of a plant cell to another, resulting in tobacco plants that lack pollen and viable seeds while maintaining normal growth. This pioneering development holds promise for improving the production of hybrid seeds to enhance crop productivity and introducing seedlessness in fruit species that lack this trait, such as raspberries, blackberries, and muscadine grapes.
The researchers initiated their study within the mitochondria, the energy-producing component of plant cells. In plants, abnormalities within the mitochondrial genome can lead to the inability to produce pollen, a condition known as cytoplasmic male sterility (CMS). CMS has been effectively utilized in many important crops to produce high-yielding hybrid seeds. However, naturally occurring CMS systems suitable for large-scale hybrid seed production are limited.
In their proof-of-concept study, the NC State researchers, in collaboration with Precision BioSciences and Elo Life Systems, devised a unique strategy to investigate whether the CMS trait could be generated in tobacco, a commonly used model species in plant research.
The researchers initially relocated an essential mitochondrial gene called atp1 to the nucleus. They placed this gene under the regulatory control of a promoter that they predicted would enable its expression in all plant cells except those responsible for pollen production. Subsequently, they employed genome editing tools to permanently remove the native atp1 gene from the mitochondria.
Remarkably, their approach proved successful.
Ralph Dewey, Philip Morris Professor of Crop Science at NC State and corresponding author of the research paper, commented, “The results exceeded our expectations. The plants appeared completely normal until they began to flower, at which point they failed to produce pollen due to the lack of expression of the transferred atp1 gene. Crucially, because the original atp1 gene was deleted from the mitochondrial genome, the trait will be inherited maternally, a crucial factor for large-scale hybrid seed production.”
However, the technique’s impact extended beyond pollen production. When cross-fertilized using pollen from a neighboring normal plant, the tobacco plants unexpectedly produced small, hollow seeds, similar to the “seedless” fruits found in watermelons and grapes.
Dewey noted that his team is now working to separate these effects, allowing researchers to achieve either pollen infertility or the seedless trait alone, rather than both simultaneously.
Furthermore, Dewey emphasized that these findings are not limited to tobacco plants. The team’s next experiments will involve testing the seedless trait in tomatoes, a close relative of tobacco. They will also assess the effectiveness of their novel CMS trait in crops like rice, where hybrid seed production is essential for maximizing yields.
Dewey concluded, “Given our understanding of how the system works, there’s no reason to believe that we couldn’t effectively apply this technology to other plant species.” This groundbreaking research opens new possibilities for enhancing crop yields and introducing desirable traits in various plant species.