Engineered plants produce sex perfumes to trick pests and replace pesticides

(Nanowerk News) Using precision 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 (Plant Biotechnology, “Tunable control of insect pheromone biosynthesis in Nicotiana benthamiana“).

Critically, they have shown how the production of these molecules can be efficiently managed so as not to hinder the normal growth of plants.

Pheromones are complex chemicals that are produced and released by an organism as a means of communication. They allow members of the same species to send signals, including letting others know they are looking for love.

Farmers can hang pheromone diffusers between their plants to mimic female insect signals, trapping or harassing males to find mates. Some of these molecules can be produced by chemical processes but chemical synthesis is often expensive and produces toxic by-products.

Dr Nicola Patron, who led the new research and heads the Synthetic Biology Group at the Earlham Institute, used cutting-edge science to get plants to produce this valuable natural product. The study looked at the sex pheromones of moth species, including the orangeworm navel moth and the cotton bollworm moth (right). (Image: Earlham Institute)

Synthetic biology applies engineering principles to the building block of life, DNA. By creating genetic modules with instructions for building new molecules, Dr Patron and his team can turn plants such as tobacco into factories that only need sunlight and water.

“Synthetic biology allows us to engineer plants to make more of something they already produce, or we can provide genetic instructions that allow them to build new biological molecules, such as drugs or these pheromones,” says Dr Patron.

In this new work, the team worked with scientists at the Plant Molecular and Cell Biology Institute in Valencia to engineer tobacco species, Nicotiana benthamiana, to produce moth sex pheromones. The same factory has previously been engineered to produce Ebola antibodies and even coronavirus-like particles for use in Covid vaccines.

The group built a new DNA sequence in the lab to mimic the moth gene and introduced several molecular switches to precisely regulate its expression, effectively turning the manufacturing process on and off.

An important component of the new research is the ability to fine-tune pheromone production, because forcing plants to continuously build these molecules has its drawbacks.

“As we increase efficiency, too much energy is diverted from normal growth and development,” explains Dr Patron.

“Plants produce a lot of pheromone but can’t grow very big, which basically reduces the capacity of our production line. Our new research provides a way to more finely regulate gene expression.”

In the lab, the team began testing and fine-tuning the controls for the genes responsible for producing specific mixtures of molecules that mimic the sex pheromones of moth species, including the orange navel worm moth and the cotton bollworm.

They demonstrated that copper sulfate could be used to fine-tune gene activity, allowing them to control the timing and levels of gene expression. This is very important because copper sulfate is a cheap and readily available compound that has been approved for use in agriculture.

They can even carefully control the production of different pheromone components, allowing them to modify cocktails to better suit certain moth species.

“We have shown that we can control the expression level of each gene relative to the others,” said Dr Patron. “This allows us to control the ratio of products made.

“Getting the recipe right is very important for moth pheromones because they are often a mixture of two or three molecules in a certain ratio. Our collaborators in Spain are now extracting the plant-made pheromone and testing it in a dispenser to see how well it compares to female moths.”

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

“The main advantage of using plants is that it is much more expensive to construct complex molecules using chemical processes,” said Dr Patron. “Plants already produce a range of useful molecules that allow us to use the latest techniques to adapt and improve existing machines.

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