A tomato plant showing some injury symptoms (yellow spots on the leaves) as a result of growing under continuous light, with lamps on all the time / Aaron I. Velez-Ramirez

Scientists have developed a 24/7 party tomato that continues to plump up all night long. The trick was finding the gene that confers continuous light tolerance in wild tomatoes.

Artificial lighting has been used to help boost crop productivity, increasing the amount of natural light available each day. Pepper, lettuce, and rose plants don't mind continuous lighting at all. But these longer periods of light exposure (called photoperiods) and the subsequent expanding energy production causes cultivated tomatoes to develop potentially lethal leaf injuries -- like the mottled yellow spots pictured above. Researchers have studied these damaging conditions since the 1920s, though the phenomenon remains poorly understood.

A team led by Aaron Velez-Ramirez and Wim van Ieperen from Wageningen University in the Netherlands examined wild tomato species that can tolerate continuous light conditions -- exposing them to 24 hours of lamp lighting and analyzing their RNA and genetic sequencing data.

They found that a single gene region (or locus) on chromosome 7 confers tolerance to continuous light. They pinpointed a gene -- the chlorophyll a/b binding protein 13 (CAB-13) gene -- that had higher expression in wild species from South America than in domesticated varieties. The work was published in Nature Communications this week.

The gene is mutated in most commercial varieties, Science explains, which makes them vulnerable to 24-hour light periods and sleepless tomato injuries. When the researchers transferred the gene into modern tomato hybrid lines, the new fruits performed better under continuous lighting after a few generations -- without affecting other aspects of the fruit’s development.

"It would be like crossing a dog with a wolf and then crossing back the descendants many times with dogs to get rid of all undesirable wolf characteristics but the one you want," Velez-Ramirez explains to the Los Angeles Times. To the right is a tomato seedling growing on a rockwool block; it looks a bit orange because it’s under high-pressure sodium light.

Tomatoes are typically grown in cycles: 16-hour light, followed by 8-hour dark. Growing plants under constant light, however, could lead to yield increases of nearly 20 percent, the researchers say.

Images: Aaron I. Velez-Ramirez