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Cold Spring Harbor Lab creates sweeter tomatoes

Heirloom tomatoes (Aug. 2007)

Heirloom tomatoes (Aug. 2007) Photo Credit: Newsday File / Adam Richins

The existence of a single tomato gene that boosts the bounty and sweetness of the fruit - hypothesized for decades - has been discovered by a Cold Spring Harbor Laboratory scientist and an Israeli team.

"There are 24 chromosomes in every [tomato] cell and this gene is sitting on chromosome three," said plant geneticist Zachary Lippman, who collaborated with scientists at Hebrew University in Israel.

The gene, which had remained elusive until now, is so dominant that only one copy is needed to force the vines to robustly produce fruit and supercharge the amount of tomato sugars. Scientists are racing to find whether vitamins C, A and other nutrients are also boosted.

"As magical as it was to see this single gene effect," Lippman remarked, "the litmus test was to determine whether this means something in different varieties - and that is what we saw." In a vast range of hybrid tomatoes, all varieties produced profusely when the gene was present, he said.

The discovery has important implications, Lippman said, for backyard gardeners, commercial growers and just about anybody who loves the taste of a well-cultivated tomato. A key role of the gene is signaling two commands: Stop making leaves. Start making flowers. The fruit emerges after flowering. It is possible to produce seeds with active copies of the gene, he said.

The newly isolated gene, Lippman added, appears to be a cousin of similar ones in other crops, like rice, corn and soybeans. He dubs the gene a tomato's "fountain of youth" because it also helps keep tomatoes heartier longer.

Scientists found the gene while on a hunt for the genetic underpinnings of a principle learned more than 130 years ago: Crossing two hybrid plants often results in robust yields and vigorous offspring. The principle was interchangeably known as hybrid vigor and heterosis. No one knew what caused it.

Charles Darwin was the first to describe heterosis, but it wasn't until 1906, when Cold Spring Harbor Lab's George Shull showed how it worked in experiments involving corn.

Yet, the precise factor leading to Shull's bountiful yields remained a mystery, which is why Lippman thinks there's a gene in play that's close kin to the one he discovered in tomatoes.

The research, reported in Sunday's online edition of the journal, Nature Genetics, involved studying more than 4,000 tomato hybrids.


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