What would you say if you could have tomatoes that ripened two weeks faster than usual? Well, a genetic method, CRISPR technology, was used to tweak genes native to two popular varieties of tomato plants. CRISPR is short for “clustered regularly interspaced short palindromic repeats,” and the technology is derived from the battle between viruses and bacteria.
The research was conducted by a team at Cold Spring Harbor Laboratory (CSHL) in New York to make tomatoes flower and produce ripe fruit more than two weeks faster than commercial breeders are currently able to do.
The end result can mean more plantings per growing season, which will lead to higher yields. It also can mean that the plant can be grown in more northerly regions, which is an important attribute as the earth’s climate warms, according to the researchers at CSHL.
“Our work is a compelling demonstration of the power of gene editing — CRISPR technology — to rapidly improve yield traits in crop breeding,” says CSHL Associate Professor Zachary Lippman, who led the research. Applications can go far beyond the tomato family, he says, to include many major food crops like maize, soybean, and wheat that so much of the world depends upon.
Lippman clarifies that the technique his team recently published in Nature Genetics is about more than simply increasing yield. “It’s really about creating a genetic toolkit that enables growers and breeders in a single generation to tweak the timing of flower production and thus yield, to help adapt our best varieties to grow in parts of the world where they don’t currently thrive.”
At the heart of the method are insights obtained by Lippman and colleagues, including plant scientists at the Boyce Thompson Institute in Ithaca, NY, and in France led by Dr. José Jiménez-Gómez, about the evolution of the flowering process in many crops and their wild relatives as it relates to the length of the light period in a day. Genetic research revealed why today’s cultivated tomato plant is not very sensitive to this variable compared to wild relatives from South America. Somehow, it does not much matter to domesticated plants whether they have 12 hours of daylight or 16 hours; they flower at virtually the same point after planting.
Inhibiting expression of the SP5G gene with CRISPR causes rapid flowering, leading to earlier fruits. The team’s principal innovation — generating varieties of cherry and roma tomatoes that flower much earlier than the domesticated varieties on which they are based — arises from the observation that while domesticated plants are notably insensitive to day length, “there was some residual expression of the anti-florigen SP5G gene,” Lippman says.
This led the team to employ the gene-editing tool CRISPR to induce tiny mutations in the SP5G gene. The aim was to inactivate the gene entirely such that it did not generate any anti-florigen protein at all.
“What we’ve demonstrated here is fast-forward breeding,” Lippman says. “Now we have a simple strategy to completely eliminate daylight sensitivity in elite inbred and hybrid plants that are already being cultivated. This could enable growers to expand their geographical range of cultivation, simply by using CRISPR to rapidly ‘adapt’ tomato and other crops to more northern latitudes, where summers have very long days and very short growing seasons.”