Researchers have compared leaf oscillation within several varieties of cultivated tomatoes (Solanum lycopersicon) and their wild ancestor (Solanum pimpinellifolium). This ancestor produces small fruit with little flesh, and its domestication first started in South America during the pre-Columbian era. Tomatoes were then dispersed throughout the world as the form we are all familiar with.
Whereas the wild ancestor’s leaves oscillate with roughly a 24-hour rhythm, those of the cultivated varieties are a lot slower. They go up and down with an average period of 27 hours. After looking at what was going on within the plants, researchers proved that the EID1 gene, which plays a known role in the clock mechanism, underwent change in cultivated tomatoes. It’s like if one of the little cogs of a mechanical clock had been modified, thus affecting the time needed for the clock hands to complete a full turn.
So, without knowing it, humans have selected for tomato varieties with slower clocks. Although we already knew that artificially modifying circadian rhythms in the lab affects plant size and yield, this is the first time that a molecular change was identified in the clock during the process of plant domestication.
Now we just need to figure out what the use of a slower clock in cultivated tomatoes actually is…
Reference: Muller et al., Nature Genetics (2015)
Translation: Noriane Simon