Tomatoes do not just grow faster on a whim. They speed up when a tiny spelling mistake in their DNA gets corrected with precise tools.

A Swiss team did exactly that in a domesticated tomato line, altering SSP2, and the plants shifted into fruiting earlier while staying compact.

In a new study, the researchers show that fixing a single harmful mutation can tune the plant’s growth schedule in a predictable way.

Making genetic alterations

The tomato carried a small change in a gene called SSP2, which helps switch growing tips from making leaves to making flowers.

That switch sets the pace for fruiting, so repairing the harmful version of SSP2 nudged plants to set fruit sooner without ballooning in size.

This work comes from assistant professor Sebastian Soyk at the University of Lausanne (UNIL), whose group focuses on the genetics of flowering and plant architecture. 

“Our work shows how deleterious variants have sensitized modern genotypes for phenotypic tuning and illustrates how repairing deleterious mutations with genome editing may allow predictable crop improvement,” wrote Soyk in the report.

Changing the tomato’s SSP2 gene

During domestication, people selected traits like bigger fruit and determinate growth. That selection also dragged along unwanted DNA changes, a pattern called the cost of domestication.

A 2018 review explains how such mutations accumulate and can subtly reduce performance.

The Swiss group identified a single letter change in SSP2 that weakened the protein’s grip on DNA.

They also showed that SSP2 normally backs up a related paralog called SSP, and that redundancy eroded in domesticated tomatoes over time.

Flowering in-tomato is powered by florigen, a mobile signal encoded by the gene SINGLE FLOWER TRUSS (SFT).

Classic work showed how SFT shapes yield by balancing vegetative growth and flower production, including heterosis effects in hybrids, in a landmark paper.

SSP and SSP2 are transcription factor partners that help florigen trigger the flower program. When SSP2 is compromised, the switch gets sluggish, shoots elongate more before flowering, and early fruit set slips.

What the data shows

Once the harmful letter in SSP2 was corrected, plants produced an earlier tranche of ripe fruit under controlled conditions.

The repaired line showed compact growth and fewer flowers per truss, which channeled development toward earlier maturity.

At harvest, the repaired plants had an 8 percent higher share of fully red fruit compared with siblings carrying the uncorrected allele, and they showed an 11 percent lower sugar content by Brix.

The team scaled up measurements to make that conclusion, then reported the full trait set in the study already cited.

Domestication often narrows genetic diversity and can fix slightly harmful variants that hitchhike with useful ones. Over centuries of selection and inbreeding, those background changes can linger and affect traits in small ways.

With precise editing, breeders can now remove a specific deleterious variant without undoing the useful alleles it sits near.

That approach complements classical breeding and reduces guesswork that usually follows random mutagenesis or long cycles of recombination, as noted by the broader literature on domestication’s genetic footprints in the same 2018 review linked above.

SSP2 tomatoes and health concerns

Switzerland has maintained a moratorium on growing genetically modified crops since 2005, and lawmakers voted in June 2025 to extend it.

Swiss lawmakers backed a continuation through 2030, while also debating tailored rules for new gene editing methods.

That policy context matters because base edited plants, including those created by precise letter swaps, may fall under different legal definitions depending on jurisdiction.

The debate centers on whether an edit that could occur naturally should be regulated like older transgenic approaches that insert foreign DNA.

What this could mean next season

Earlier yield can be valuable for growers in short seasons, high latitude regions, or indoor systems where turn time is money.

Compact plants with predictable flowering can be spaced and pruned more efficiently, which helps planning.

There is a tradeoff to watch, since lower Brix means less sweetness. Breeders can mitigate that by stacking the SSP2 repair with sugar related alleles or by targeting edits to environments where early red fruit is worth more than peak sweetness.

The SFT pathway is a central timing circuit in tomato, and tuning it has a long track record in yield optimization.

Heterozygosity at SFT can boost yield markedly in hybrids, showing how small shifts in flowering control ripple into fruit set and harvest timing, as shown in the 2010 paper cited above.

The SSP and SSP2 pair acts just upstream of these outcomes, guiding meristems to switch from leafy growth to flower clusters on schedule.

Repairing SSP2 did not raise total fruit number in this experiment, but it pulled ripening forward and tightened the plant’s form, which is a clear lever for scheduling.

The study is published in Nature Genetics.

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