A study carried out by scientists from the University of Almeria, published in the PNAS magazine, has discovered the genetic keys that allowed tomato to grow to its current size, which is 100 times bigger than its South American ancestor., the Solanum pimpinellifolium.
According to the study, the size of the tomato is determined by the seed compartments that make up the ripe fruit. "The extreme size of the tomato fruit that evolved from its small wild ancestor is mainly determined by the number of carpels of a flower, which are the compartments of the seeds that form the ripe fruit," the authors explain.
Using sequencing and CRISPR-Cas9 techniques, the research team managed to isolate a protein involved in this growth called 'excessive number of floral organs' (ENO). It is a transcription factor, which binds to specific DNA sequences to control the transcription of genetic information.
Increased floral meristem
The researchers verified that ENO regulates the size of the tomato through the floral meristem development network, the tissue of the plant that houses the stem cells that give rise to flowers.
Their findings reveal that a mutation in this protein affects the expression of certain areas of the genetic regions involved in creating the cavities (derived from the carpels) where the seeds are housed.
In vitro tests also show that ENO directly regulates the expression domains of these genetic regions to maintain the proper functioning or floral homeostasis of stem cells.
"Our study also shows that a mutation in the ENO promoter protein was selected during domestication to improve tomato size, indicating that transcriptional changes in key regulators have significant effects on agronomic traits," the authors conclude.