Easy-to-grow, sturdy petunia plants produce flowers with a great variety of spectacular colors and a captivating scent. The Maya in Mexico and Inca in Peru believed that the scent of petunias had the power to ward off underworld monsters and spirits and their buds were bound together for magical drinks.
Now, scientists at the Hebrew University of Jerusalem have unlocked the secret behind the blossom’s captivating aroma – tracing it back to a single gene called PhDEF. The gene not only shapes the flower’s petals but also triggers the production of alluring fragrances that attract pollinators, especially bees and also certain birds.
Prof. Alexander Vainstein from HU’s Robert H. Smith Faculty of Agriculture, Food, and Environment in Rehovot said his team’s discovery could eventually revolutionize the fragrance industry, biotechnology, and horticulture, offering new ways to enhance floral scents without changing the flower’s natural beauty.
Unlocking the secrets behind the scent of flowers
“It used to be thought that if the scent of flowers is more powerful, the flowers have a short life and then dry up, but we found that it isn’t true; there is no genetic connection between the two,” the Russian-born biochemist told The Jerusalem Post in an interview.
“I chose petunias to study because they are easy to grow, produce a lot of molecules for scent production, can be manipulated genetically, and are big, colorful flowers with many variations,” he noted.
“We proved that certain genes are responsible not only for making the flower itself but also for ensuring that there is enough scent to attract pollinators. Without bees and other birds that spread the pollen, there will be many fewer fruits and vegetables. We also showed the connection between color and scent of flowers.”
Temperature and light affect flowers and their production of scent. “We have to work under strict and controlled conditions. Machines can identify volatile molecules that produce the odor in flowers,” he explained.
The basic-science discovery can be used in the future to benefit the perfume industry and enhance the production of scent in flowers to attract more pollinators. Bees can’t easily see color, especially from afar, but the flowers’ aroma is very important. “Like a bull’s eye, the scent is much stronger in the center of the flower where pollination occurs, so this characteristic is very important.”
Of South American origin, the popular flower got its name from the French, which took the word pétun – “tobacco,” to which it is related, as are tomatoes, potatoes, chili peppers, and gooseberries. Most petunias are hybrids. They need at least five hours of sunlight daily and do best in moist soil and conditions of low atmospheric humidity.
THE STUDY, published in The Plant Cell under the title “The homeotic gene PhDEF regulates production of volatiles in petunia flowers by activating EOBI and EOBII,” shows how PhDEF, a homeotic gene (that controls the pattern of body formation during early embryonic development of organisms) – which is known for its role in petal formation – also plays an essential role in activating scent production at later stages of flower development.
Using advanced genetic analysis and viral-induced silencing of genes, the research team proved that suppressing PhDEF significantly reduced volatile emissions, thus weakening the floral scent.
“In this study, we show that PhDEF orchestrates not only early but also late stages of flower development, as revealed by its effect on scent production in petunias,” the HU researcher added. “Our findings show that PhDEF is not responsible just for defining petal identity but also for coordinating the production of scent compounds critical for pollination.
“This dual functionality suggests that petunia flowers have evolved an integrated regulatory mechanism to optimize their attraction to pollinators. Our findings underscore the importance of the gene in petunia flower development from initiation to maturation and in coordinating petal specification and the establishment of pollination-related traits.”
The team identified PhDEF as a key activator of EOBI and EOBII, two major transcriptional regulators of floral scent production, along with other biosynthetic genes responsible for the emission of volatile compounds.
By activating these pathways, PhDEF ensures the release of phenylpropanoid-based volatiles that make flowers more attractive to pollinators. Suppressing PhDEF led to a notable drop in the production of essential scent compounds including methyl benzoate and benzyl alcohol.
Despite this reduction, the study found that PhDEF suppression did not change the form of the petals and the relationships between their structures, indicating that scent production can be manipulated genetically without affecting the flower’s structure.
Vainstein has turned the flower “baby’s breath” red, instead of just white, and he has worked with roses to get them to generate a stronger scent. He also has a start-up company to conduct genomic modification that gives red, green, and even chili peppers more pigmentation because these create more healthful antioxidants for consumption.
Asked if he has favorites among blooms, he said, “Petunias are the best to work with in the lab, but I have no favorites – but my wife prefers roses. One can’t make a bouquet of petunias.”
The findings open new possibilities for enhancing floral scent in commercial flower varieties or modifying scent profiles for agricultural crops that rely on pollination, Vainstein said. “This discovery increases our knowledge of plant biology and offers potential applications for breeding more resilient and pollinator-friendly crops.”