The Spanish biologist did this two decades ago, but he did not know to what extent. He observed that some microbes from Alicante used a type of tiny scissors to defend themselves against invading viruses by cutting up their genetic material. French biochemist Emmanuelle Charpentier and her American colleague Jennifer Doudna realized in 2012 that these microbial scissors, called CRISPR, could be used to rewrite the DNA of any species. Both won for this reason in 2020. The first CRISPR therapies, approved a year ago, . And this Wednesday the latest feat of this technology is presented: tastier tomatoes, with the same size. For some, the holy grail of agriculture.
Chinese scientist Jinzhe Zhang remembers the happiness he felt the day he tried his genetically modified tomatoes for the first time. “They just taste like tomato, but a little sweeter,” he celebrates. To understand their joy, we have to go back more than 5,000 years, when farmers in the region that is now Peru and Ecuador domesticated the wild ancestors of the tomato, just one centimeter long. The fruit came to Europe in the 16th century, with one characteristic: if the largest ones were selected, flavor was lost. Centuries of this practice have culminated in the widespread panorama in today’s supermarkets: the tomatoes are splendid, up to 100 times larger than the ancestral ones, but tasteless.
An international consortium published a report on tomato in 2012. Five years later, a team of scientists identified the genetic regions associated with 13 chemical compounds associated with flavor, abundant in ancestral varieties, but almost missing in commercial ones. The discovery was so promising that it was featured in the magazine Science. This Wednesday, Jinzhe Zhang’s team announces that it has used CRISPR scissors to inactivate two genes, SlCDPK27 and SlCDPK26, which act as brakes on the production of sugars during fruit ripening, probably to ensure an adequate supply of energy for development. rear of the seeds. The result is a 30% increase in fructose and glucose levels, without reducing size or yield. Their study is published.
Increasing the sugars in the fruit, however, comes at a price: fewer seeds form and they are lighter. Zhang, from the Beijing Institute of Vegetables and Flowers, emphasizes that its germination is normal, so he is confident in its viability in the market. The first agricultural product modified with CRISPR and marketed for human consumption was precisely a tomato, edited to contain high amounts of gamma-aminobutyric acid, a substance capable of reducing blood pressure and calming the nervous system. The fruit, developed by a company promoted by the University of Tsukuba (Japan), online on September 15, 2021.
The leader of the new research is , general director of the Institute of Agricultural Genomics of Shenzhen (China), a giant with 300 workers. Huang notes that his team has applied for a patent on the use of these two genes to increase sugars in fruit. Their goal is to try a similar modification in apples, pears and oranges, which share the same genes. Chinese scientists are already working with companies to develop commercial varieties of tomatoes with the two genes inactivated. “I visited Spain in 2017 and the tomatoes were very good!” Huang recalls.
That year, the Chinese scientist attended a conference in Valencia, at the Institute of Molecular and Cellular Biology of Plants, another of the key centers in the future of tomatoes. The geneticist works there, who has collaborated with Huang in the past in the identification of genetic regions associated with flavor. The Spaniard applauds the new study, but is cautious. He warns that in the tasting groups in Shenzhen and Beijing, with about 100 people each, around 60% noticed the greater sweetness of the tomatoes, but the remaining 40% did not. “A normal citizen hardly notices the difference,” he says.
Granell believes that the room for improvement is much greater. The concentration of sugars in tomatoes is measured in degrees Brix. A normal fresh tomato usually has 4 degrees, which means that around 4% of the fruit is made up of glucose, fructose and sucrose. Granell highlights that the new genetic modification achieves an increase of approximately 4 to 5 degrees Brix in tomatoes weighing about 100 grams, but it is still far from the 7 degrees Brix observed in traditional European varieties of up to 300 grams. Tiny cherri tomatoes reach 12 degrees Brix. “This means that there is a much greater potential for tomatoes to be sweeter, if we manage to combine the effect on several genes,” emphasizes Granell, who coordinates a European project to develop tomatoes of better quality, more resistant and with better flavor. .
The Valencia researcher emphasizes that genetics is not the only way to increase flavor. Granell collaborates with the Granada La Palma cooperative, which grows , one of the most expensive in Spain. It is a Japanese variety that reaches 30 euros per kilo thanks to its sweetness, up to 9 degrees Brix, achieved through strict control of irrigation, nutrients, light and temperature.
The geneticist shows his enthusiasm for the progress of Chinese researchers. He says that back in 1994 he participated in a project to try to produce tastier tomatoes without reducing their size. “We didn’t achieve it,” acknowledges this expert, professor of Genetics at the University of Almería. His team and that of a seed company grew thousands of plants, obtained by crossing different varieties, without success. Time and again they came face to face with the link between the genes involved in size and those involved in flavor. Lozano applauds “the ingenuity” of Sanwen Huang’s group to find the genetic key and make a sophisticated change using CRISPR scissors.
“This new study represents an important contribution to a classic problem: developing varieties with good fruit size, but with flavor,” he says. Lozano himself uses the CRISPR tool to modulate the acidity and vitamins of tomatoes. “Organic acids, such as citric and malic, also have to be in the appropriate concentration. If there is no acidity, the tomato would taste like candy and nobody wants candy flavor, they want tomato flavor,” he warns.
