Engineered plants produce sexual fragrances to fool pests and replace pesticides

Using precise gene engineering techniques, researchers at the Earlham Institute in Norwich have been able to turn tobacco plants into solar-powered factories for moth sex pheromones.

Crucially, they have shown how the production of these molecules can be efficiently managed so as not to impede normal plant growth.

Pheromones are complex chemicals that an organism produces and releases as a means of communication. They allow members of the same species to send signals, which includes letting others know that they are looking for love.

Farmers can hang pheromone dispersants between their crops to mimic the signals of female insects, trapping or distracting males from finding a mate. Some of these molecules can be produced through chemical processes, but chemical synthesis is often expensive and produces toxic byproducts.

Dr. Nicola Patron, who led this new research and chair of the synthetic biology group at the Earlham Institute, is using the latest science to get plants to produce these valuable natural products.

Synthetic biology applies engineering principles to the building blocks of life, DNA. By creating genetic units with the instructions to build new molecules, Dr. Patron and her group can transform a plant like tobacco into one that only needs sunlight and water.

“Synthetic biology can allow us to engineer plants to produce a lot of what they’ve already produced, or we can provide the genetic instructions that allow them to build new biological molecules, like drugs or these pheromones,” said Dr. Patron.

In this latest work, the team worked with scientists at the Institute of Cell Biology and Plant Molecules in Valencia to engineer a species of tobacco, Nicotiana benthamiana, to produce moth sex pheromones. The same plant was previously engineered to produce Ebola antibodies and even coronavirus-like particles for use in COVID vaccines.

The group built new strands of DNA in the lab to mimic the moth’s genes and introduced a few molecular switches to finely regulate its expression, effectively turning the manufacturing process on and off.

An important component of the new research was the ability to tune the production of pheromones, as forcing plants to continually build up these molecules has its drawbacks.

“As efficiency increases, a lot of energy is diverted away from normal growth and development,” explained Dr. Patron.

“Plants produce a lot of pheromone but are unable to grow very large, which essentially reduces the capacity of our production line. Our new research provides a way to regulate gene expression with more precision.”

In the lab, the team set out to test and improve the control of genes responsible for producing a cocktail of specific molecules that mimic the sex pheromones of moth species, including the orange worm and the cotton bollworm.

They showed that copper sulfate can be used to finely tune gene activity, allowing them to control both the timing and the level of gene expression. This is especially important because copper sulfate is a cheap and readily available compound that has already been approved for use in agriculture.

They were even able to carefully control the production of different pheromone ingredients, which allowed them to adjust the cocktail to better suit specific species of moth.

“We’ve shown that we can control the expression levels of each gene relative to the others,” said Dr. Patron. “This allows us to control the proportion of products that are made.”

“Getting this recipe right is especially important for moth pheromones because they are often a mixture of two or three molecules in specific proportions. Our collaborators in Spain are now extracting plant-made pheromones and testing them in dispensers to see how well they compare to female moths.”

The team hopes their work will pave the way for plants to be used routinely to produce a wide range of valuable natural products.

“The main advantage of using plants is that building complex molecules using chemical processes can be much more affordable,” said Dr. Patron. “Plants produce a range of molecules that are already useful so we can use the latest technology to adapt and improve existing machines.”

“In the future, we may see greenhouses filled with plant factories — providing a greener, cheaper, and more sustainable way to manufacture complex molecules.”

Publication of the research in the journal plant biotechnology.