Round or oval? This gene decides tomato shape

March 14th, 2008 - 11:43 am ICT by admin  

Washington, March 14 (IANS) Crop scientists have cloned a gene that governs the shape of tomatoes, a discovery that could help unravel the mystery behind the huge differences among edible fruits and vegetables. The gene, dubbed SUN, is only the second ever found to play a significant role in the elongated shape of various tomato varieties, said Esther van der Knaap of Ohio State University.

Details of the discovery have been published in the latest issue of the journal Science.

One of the first pieces in Knaap’s fruit-development puzzle is SUN, which takes its name from the “Sun 1642″ cultivated variety where it was found - an oval-shaped tomato with a pointy end.

Once SUN was identified, the next step involved proving whether this gene was actually responsible for causing changes in fruit shape.

Then Knaap and her team conducted several plant-transformation experiments. When the SUN gene was introduced into wild, round fruit-bearing tomato plants, they ended up producing extremely elongated fruit.

Conversely when it was “knocked out” of elongated fruit-bearing plants, they produced round fruit similar to the wild tomatoes.

“SUN doesn’t tell us exactly how the fruit-shape phenotype is altered, but what we do know is that turning the gene on is very critical to result in elongated fruit,” she said.

“We can now move forward and ask the question: Does this same gene, or a gene that is closely related in sequence, control fruit morphology in other vegetables and fruit crops?”

Something else Knaap and her team found out is that SUN encodes a member of the IQ67 domain of plant proteins, called IQD12, which they determined to be sufficient - on its own - to make tomatoes elongated instead of round during the plant transformation experiments.

Another unique characteristic of SUN gene is that it affects fruit shape after pollination and fertilization, with the most significant morphological differences found in developing fruit five days after plant flowering.

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