It’s a common complaint in the produce aisle: today’s tomatoes may be big, but they’re tasteless. Now researchers say they can fix the problem by tweaking genes that affect sugar levels in the fruit.
While their wild relatives produce small, sweet fruits, industrially grown domesticated tomatoes have been bred for high yields, resulting in varieties 10-100 times larger.
Now scientists in China say they have identified two genes that put a brake on sugar production in tomatoes during ripening, and have created gene-edited versions of domesticated varieties to produce fruit that is large but also sweet.
Prof Sanwen Huang, the director-general of the agricultural genomics institute at the Chinese Academy of Agricultural Sciences, Shenzhen, said it was necessary to balance the needs of consumers with those of producers and farmers.
“Since farmers want bigger tomatoes and higher yields, consumers want sweeter tomatoes,” he said. “Our discovery of the sugar brake genes leads to [breeding of a] sweeter tomato without sacrificing fruit size and yield, which breaks the negative relationship between yield and quality.”
Write in the journal Naturethe researchers describe how they examined the genomes of wild and cultivated tomato plants for the first time, and identified two similar genes associated with the sugar content of the fruit. They say the versions of these genes associated with high sweetness are common in wild tomato plants but have been largely lost in modern varieties.
Further work revealed that the versions of the genes found in domesticated tomato plants enabled the production of an enzyme that marked another sugar-making enzyme for destruction inside cells. In contrast, the versions of these genes found in wild plants limited the production of this enzyme, resulting in sweeter tomatoes.
When the team the gene editing tool Crispr-Cas9 to make precise changes to the DNA of domesticated tomato plants, to prevent these genes from working properly, they found that the resulting fruit had up to 30% higher sugar content than that of unmodified plants. Unexpectedly, however, there was no significant difference in fruit weight or yield. While the gene-edited tomatoes had fewer, lighter seeds, they germinated as normal.
The researchers say their work suggests that the two genes work as sugar brakes during fruit ripening, probably to ensure that there is enough energy for the development of seeds.
Huang said the new tomatoes could end up in supermarkets within three to five years; the team noted that other gene-edited tomatoes are already available in Japan.
However, it may be some time before others can taste the fruits of such science: while new laws support it cultivation of gene-edited crops in England and Wales, secondary legalization is necessary to implement the law not yet passed.
