The tomato fruit has a reservoir of healthy properties; it is low in calories and excellent for weight loss. It was popular in Aztec times around 700 A.D, but it became systematically cultivated for the first time in Central and South America (Peru). Spanish conquistadors brought tomatoes from Peru back to Europe in the 16th century with the name “tomatl,” an Aztec word. The Italians gave them the name “golden apple” for the yellow or orange color of the mature tomato at that time, while the aphrodisiac properties of the tomato gave it the early French name “pomme d’amour,” or “love apple.” In the 18th century, migrants from Italy to America made tomatoes popular in North America. Today, millions all over the world enjoy tomatoes fresh, canned, diced, or stewed.
Image courtesy Zoe Hilioti
The tomato is a “functional food,” meaning its consumption goes beyond basic nutrition. It has bioactive components which may reduce the risk of certain types of cancers (e.g. prostate, lung, stomach, breast, cervical, rectal, esophageal, oral and pancreatic), degenerative diseases like age-related macular degeneration, and it can lower the amount of oxidized LDL-cholesterol. Tomatoes combat the formation of free radicals produced by the normal metabolism of cells. Free radicals can lead to DNA damage that in turn leads to cancer. The tomato’s disease-preventing potential is due to the presence of different antioxidant molecules such as carotenoids, particularly lycopene, ascorbic acid (collagen production), folic acid, vitamin E, choline, and phenol compounds, particularly flavonoids.
Tomatoes are a dietary source of soluble and insoluble dietary fibers constituted by pectins, hemicelluloses, and cellulose. Consumers of fresh tomatoes tend to purchase them based on appearance and not nutritional information. Most of the time, however, there are differences in the nutritional value among varieties of fresh produce.
Research in genome editing created the opportunity to target specific genes involved in different molecular pathways with the aim to produce a local genetic variation that will increase the repertoire of interesting plant characteristics. Researchers from the Institute of Applied Biosciences of CERTH in Greece developed the first Zinc Finger Nuclease (ZFN) technology for tomato1 breeding. The new technology mimics Nature’s way of introducing genetic variation(s) in the DNA cut sites during the evolution of species with the difference that is more efficient and targeted.
A follow-up study in eight ZFN-produced tomato lines conducted in collaboration with the University of Algarve, Faculty of Science and Technology in Portugal and the Technological Educational Institution of Crete in Greece to analyze the fruit nutrient content. Based on targeted and untargeted analyses,2 tomatoes carrying genetic mutations in the master transcription factor L1L4 (NF-YB) gene had a significant variation in metabolic profiles. The metabolite “tailored” tomatoes had variable levels of vitamin C, increased antioxidant content, low oxalic acid (anti-nutrient) and high fructose to glucose ratio, which makes them suitable for a diabetic diet. Specifically, after targeted and untargeted analysis of fruits and seeds, it was found that the L1L4 gene is a negative regulator of fiber, fructose, succinic and shikimic acid biosynthesis, and a positive regulator of citric and oxalic acid biosynthesis.
The ZFN technology can serve as a powerful tool in the breeder’s toolbox for genome editing in a precise, efficient, specific, and transgene-free manner, with the potential to change metabolite composition for specific nutritional and/or anti-nutritional needs.