🍆 Genetic technology enables larger and tastier tomatoes and eggplants

• Researchers have discovered genes that control how large tomatoes and eggplants can grow.
• New techniques in gene editing can lead to the development of new varieties of traditional tomatoes and eggplants that are both larger and tastier.
• The research can support agriculture in areas where local varieties are currently too small for large-scale production.

Researchers map genes controlling fruit size

Scientists from Johns Hopkins University and Cold Spring Harbor Laboratory have identified specific genes that control the size of fruits in plants from the nightshade family, such as tomatoes and eggplants. The research findings could lead to the development of new varieties that are both larger and more flavorful.

"Once gene editing is done, only one seed is needed to start a change," says Michael Schatz, geneticist at Johns Hopkins University who also worked on the Telomere-to-Telomere project for the human genome. "With the right approvals, we could send a modified seed to Africa or wherever it's needed and open entirely new agricultural markets."

The research is part of a larger project aimed at mapping complete genomes for 22 crops in the nightshade genus, including tomatoes, potatoes, and eggplants.

Genome analyses reveal evolutionary patterns

Using computational analysis, researchers compared the genome maps and tracked how the genes evolved over time. They discovered that more than half of the genes had been duplicated at some point in the past.

"Over tens of millions of years, there is a constant reshaping of DNA sequences being added and disappearing," explains Schatz. "The same process can occur for gene sequences, where entire genes duplicate or disappear."

To investigate the effects of these changes, researchers at Boyce Thomson Institute used CRISPR-Cas9 technology to modify one or both copies of a gene. Their colleagues at Cold Spring Harbor grew the modified plants to see how the changes affected the mature plants.

Specific genes identified for fruit size

The genetic duplicates, or paralogs, proved to be important for traits such as flowering time, fruit size, and fruit shape. When researchers turned off both copies of the CLV3 gene paralogs in an Australian nightshade, it resulted in plants with irregular and disorganized forms. But careful editing of just one copy of CLV3 led to larger fruits.

"Having complete genome sequences for these species is like having a new treasure map. We can see where and when one genetic path differs from another and then explore that place in the genetic information," says Katharine Jenike, who compiled the genome sequences and was a doctoral student in Schatz's laboratory during the research.

In the African eggplant, researchers identified a gene, SaetSCPL25-like, that controls the number of seed chambers or locules inside the fruit. When they edited the SaetSCPL25-like genes in the tomato plant, researchers could grow tomatoes with more locules, resulting in larger tomatoes.

"This work shows the importance of studying many species together," says Schatz. "We leveraged decades of work in tomato genetics to rapidly advance African eggplants, and along the way we found entirely new genes in African eggplants that in turn advance tomatoes. We call this 'pangenetics,' and it opens endless possibilities to bring many new fruits, foods, and flavors to dinner tables around the world."

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