Tomato's hidden mutations revealed in study of 100 varieties

June 17, 2020

Human appetites have transformed the tomato - DNA and all. After centuries of breeding, what was once a South American berry roughly the size of a pea now takes all sorts of shapes and sizes, from cherry-like to hefty heirloom fruit.

Today, scientists are teasing out how these physical changes show up at the level of genes - work that could guide modern efforts to tweak the tomato, says Howard Hughes Medical Institute Investigator
He and colleagues have now identified long-concealed hidden mutations within the genomes of 100 types of tomato, including an orange-berried wild plant from the Galapagos Islands and varieties typically processed into ketchup and sauce.

Their analysis, described June 17, 2020, in the journal Cell, is the most comprehensive assessment of such mutations - which alter long sections of DNA - for any plant. The research could lead to the creation of new tomato varieties and the improvement of existing ones, Lippman says. A handful of the mutations his team identified alter key characteristics, like flavor and weight, the researchers showed.

Previous studies have long shown that these mutations exist in plant genomes, says Lippman, a plant geneticist at Cold Spring Harbor Laboratory. "But until now, we didn't have an efficient way to find them and study their impact," he says.

A window into the genome

Mutations, or changes, in the four types of DNA letters carried within an organism's cells can alter its physical characteristics. Scientists studying plants have generally focused on a small, tractable kind of mutation, in which one DNA letter is swapped for another.

The mutations Lippman's team studied are much bigger - they modify DNA's structure by copying, deleting, inserting, or moving long sections of DNA elsewhere in the genome. These mutations, also called structural variations, occur throughout the living world. Studies in humans, for example, have linked these variations to disorders such as schizophrenia and autism.

Scientists can identify mutations by reading out the letters of DNA using a technique known as genetic sequencing. Limitations in this technology, however, have made it difficult to decode long sections of DNA, Lippman says. So researchers haven't been able to capture a complete picture of structural mutations in the genome.

Even so, plant geneticists have suspected that these mutations contribute significantly to plants' traits, says Michael Purugganan, who studies rice and date palms at New York University and was not involved in the new study. "That's why this paper is so exciting," he says. Lippman's team not only found these mutations in tomato and its wild relatives, but also determined how they function within the plants, he says.

A guide for future tomatoes

The new study, a collaboration with Michael Schatz at Johns Hopkins University and others, identified more than 200,000 structural mutations in tomatoes using a technique called long-read sequencing. Lippman likens it to looking through a panoramic window at large sections of the genome. By comparison, more conventional sequencing offered only a peephole, he says.

The majority of the mutations they found do not change genes that encode traits. But what's clear, Lippman says, is that many of these mutations alter mechanisms controlling genes' activity. One such gene, for instance, controls tomato fruit size. By modifying DNA structure ¬- in this case, the number of copies of the gene - Lippman's team was able to alter fruit production. Plants lacking the gene never made fruit, while plants with three copies of the gene made fruit about 30 percent larger than those with just a single copy.

Lippman's team also demonstrated how DNA structure can influence traits in an example he calls "remarkably complex." They showed that four structural mutations together were needed for breeding a major harvesting trait into modern tomatoes.

These sorts of insights could help explain trait diversity in other crops and enable breeders to improve varieties, Lippman says. For instance, perhaps adding an extra copy of the size gene to

"One of the holy grails in agriculture is to be able to say, 'If I mutate this gene, I know what the output will be,'" he says. "The field is making important steps toward this kind of predictable breeding."

Michael Alonge et al. "Major impacts of widespread structural variation on gene expression and crop improvement in tomato." Cell. Published online June 17, 2000.

Howard Hughes Medical Institute

Related Science Articles from Brightsurf:

75 science societies urge the education department to base Title IX sexual harassment regulations on evidence and science
The American Educational Research Association (AERA) and the American Association for the Advancement of Science (AAAS) today led 75 scientific societies in submitting comments on the US Department of Education's proposed changes to Title IX regulations.

Science/Science Careers' survey ranks top biotech, biopharma, and pharma employers
The Science and Science Careers' 2018 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Science in the palm of your hand: How citizen science transforms passive learners
Citizen science projects can engage even children who previously were not interested in science.

Applied science may yield more translational research publications than basic science
While translational research can happen at any stage of the research process, a recent investigation of behavioral and social science research awards granted by the NIH between 2008 and 2014 revealed that applied science yielded a higher volume of translational research publications than basic science, according to a study published May 9, 2018 in the open-access journal PLOS ONE by Xueying Han from the Science and Technology Policy Institute, USA, and colleagues.

Prominent academics, including Salk's Thomas Albright, call for more science in forensic science
Six scientists who recently served on the National Commission on Forensic Science are calling on the scientific community at large to advocate for increased research and financial support of forensic science as well as the introduction of empirical testing requirements to ensure the validity of outcomes.

World Science Forum 2017 Jordan issues Science for Peace Declaration
On behalf of the coordinating organizations responsible for delivering the World Science Forum Jordan, the concluding Science for Peace Declaration issued at the Dead Sea represents a global call for action to science and society to build a future that promises greater equality, security and opportunity for all, and in which science plays an increasingly prominent role as an enabler of fair and sustainable development.

PETA science group promotes animal-free science at society of toxicology conference
The PETA International Science Consortium Ltd. is presenting two posters on animal-free methods for testing inhalation toxicity at the 56th annual Society of Toxicology (SOT) meeting March 12 to 16, 2017, in Baltimore, Maryland.

Citizen Science in the Digital Age: Rhetoric, Science and Public Engagement
James Wynn's timely investigation highlights scientific studies grounded in publicly gathered data and probes the rhetoric these studies employ.

Science/Science Careers' survey ranks top biotech, pharma, and biopharma employers
The Science and Science Careers' 2016 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Three natural science professors win TJ Park Science Fellowship
Professor Jung-Min Kee (Department of Chemistry, UNIST), Professor Kyudong Choi (Department of Mathematical Sciences, UNIST), and Professor Kwanpyo Kim (Department of Physics, UNIST) are the recipients of the Cheong-Am (TJ Park) Science Fellowship of the year 2016.

Read More: Science News and Science Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to