Using precision genetic engineering techniques, researchers at the Earlham Institute in Norwich have managed to turn tobacco plants into sex pheromone factories that drive away insects, without the need for pesticides. The discovery was published in the journal Plant Biotechnology.

Furthermore, they demonstrate that the production of these molecules can be managed efficiently so as not to impair normal plant growth.

Pheromones are complex chemicals produced and released by an organism to communicate. They allow members of the same species to send signals, which includes letting others know that they are looking for love.

Pheromone spreaders can be hung in plantings to mimic female insect signals, trapping or distracting males from finding a mate. Some of these molecules can be produced by chemical processes, but chemical synthesis is usually expensive and produces products that can be toxic.

But genetic engineering and cutting-edge science can make this process happen naturally so that the plants themselves produce this alternative to pesticides. That’s what the team led by Nicola Patron, who heads the Synthetic Biology Group at the Earlham Institute, did.

A factory that only needs water and sun

Synthetic biology applies engineering principles to the building blocks of life, DNA. By creating genetic modules with the instructions to build new molecules, this researcher and her team turned a plant like tobacco into a factory that only needs sunlight and water.

In this latest work, the team worked with scientists from the Institute of Cellular and Molecular Biology of Plants at the Polytechnic University of Valencia to engineer a species of tobacco, Nicotiana benthamiana, to produce moth sex pheromones. The same plant was previously designed to produce Ebola antibodies and even coronavirus-like particles for use in Covid vaccines.

The Group built new DNA sequences in the lab to mimic the moth’s genes and introduced some molecular switches to precisely regulate their expression, effectively turning the manufacturing process on and off.

An important component of the new research was the ability to fine-tune pheromone production, as forcing plants to continually build these molecules has its downsides.

“As we increase efficiency, a lot of energy is diverted from normal growth and development,” explained Patron.

“The plants are producing a lot of pheromones, but they can’t get too big, which basically reduces the capacity of our production line. Our new research provides a way to regulate gene expression much more subtly.”

An anti-moth cocktail

In the lab, the team began testing and refining the control of the genes responsible for producing the mixture of specific molecules that mimic the sex pheromones of moths, including caterpillars and cotton moths.

They showed that copper sulfate could be used to adjust gene activity, allowing them to control the timing and level of gene expression. This is particularly important because copper sulfate is an inexpensive and readily available compound that has already been approved for use in agriculture.

They were able to carefully control the production of different components of the pheromone, allowing them to modify the cocktail to better suit specific moth species.

“Getting the recipe right is particularly important for moth pheromones, as they are usually a mixture of two or three molecules in specific proportions. Our collaborators in Spain are now extracting the pheromones made from plants and testing them in dispensers to see how they compare to female moths.”

The team hopes that their work will pave the way for the routine use of plants to produce a wide range of valuable natural products.

“In the future, we may see greenhouses full of plant factories providing a greener, cheaper and more sustainable way to produce complex molecules,” they say.