Farmers could soon be growing tomatoes bunched like grapes in a storage unit, on the roof of a skyscraper, or even in space. These new “urban agriculture tomatoes” were developed by a team at Cold Spring Habor Laboratory that is focused on engineering a wider variety of crops that can be grown in urban environments or other places not suitable for plant growth.
These new gene-edited tomato plants look nothing like the long vines you normally see. The most notable feature is their bunched, compact fruit. They resemble a bouquet whose roses have been replaced by ripe cherry tomatoes. They also mature quickly, producing ripe fruit that's ready for harvest in under 40 days.
"This demonstrates how we can produce crops in new ways, without having to tear up the land as much or add excessive fertilizer that runs off into rivers and streams," explained Zach Lippman, senior author of a paper explaining the process that was published in Nature Biotechnology today.
Lippman and his colleagues created the new tomatoes by fine-tuning two genes that control the switch to reproductive growth and plant size, the SELF PRUNING (SP) and SP5G genes, which caused the plant to stop growing sooner and flower and fruit earlier. But Lippman's lab knew it could only modify the SP sister genes only so much before trading flavor or yield for even smaller plants.
"When you're playing with plant maturation, you're playing with the whole system, and that system includes the sugars, where they're made, which is the leaves, and how they're distributed, which is to the fruits," Lippman said.
Searching for a third player, Lippman's team recently discovered the gene SIER, which controls the lengths of stems. Mutating SIER with the CRISPR gene-editing tool and combining it with the mutations in the other two flowering genes created shorter stems and extremely compact plants.
The team is perfecting the technique and hopes other will be inspired to try it on other fruit crops like kiwi.
Image: When three specific genetic mutations are combined and tuned just right, scientists can turn tomato plants into extremely compact bushes ideal for urban agriculture. Just two of these mutations (insert, left) shortens the normally vine-like plants to grow in a field, but all three (insert, right) causes their fruits to bunch like grapes. Researchers cut away the plant's leaves for a clearer view of the new tomatoes. Image courtesy of Lippman lab/CSHL, 2019.