Natural sex pheromones instead of pesticides: the study to make plants produce them directly

For now, the experiment has been conducted on tobacco plants. Some specimens have been genetically engineered to produce a seductive scent of insect sex pheromones: an ingenious method to confuse would-be parasites e drastically reduce the need to resort to pesticides for the most different crops. One method, that of sexual confusionactually already used in organic farming, for example against lepidoptera, but using chemically made pheromones: the new study promises to pave the way for their more sustainable production.

Let’s proceed in order: using precision genetic engineering techniques, a group of researchers from theEarlham Institute in Norwichin England, has essentially succeeded, as a note from the institute explains, in “transforming tobacco plants into ‘factories’ of sex pheromones of moths“, “factories” powered by sunlight. I pheromones are complex chemicals produced and released by an organism as a means of communication for different purposes. They allow for example members of the same species – over all mammals, homo sapiens including, and indeed some insects – to send signals. They are chemical messengers that regulate some relationships between animals: among these, even those related to mating and reproduction.

“The farmers they can hang pheromone dispersers among their crops to mimic the signals of female insects, trapping or distracting males from finding a mate – continues the Earlham Institute – some of these molecules can be produced by chemical processes but chemical synthesis is often expensive and creates toxic by-products”. In short, it is not an acceptable or sustainable solution, because if on the one hand it reduces the need to use pesticides, on the other it does so thanks to the chemical production of pheromones. Now the research group , driven by Nicholas Patron who also chairs the institute’s Synthetic Biology Group, demonstrated how the endogenous production of these molecules directly by some plant species can be managed efficiently so as not to hinder their normal growth. So that they can be used as reservoirs of natural pheromones.

“There synthetic biology can afford to engineer plants to get much more out of something they’ve already made, or we can provide the genetic instructions that allow them to build new biological moleculeslike medicines or like these pheromones,” Patron explained. Essentially, by creating genetic modules containing instructions for building new molecules, Dr. Patron and her team can turn a plant like tobacco into a natural pheromone reactor that requires just sunlight and water.

In this latest work, the team collaborated with scientists from the Institute of Cellular and Molecular Biology of Plants in Valencia to genetically modify a species of tobacco, Nicotiana benthamiana, so as to make it precisely able to produce sexual pheromones of two species of moths. The same plant, evidently predisposed for this kind of intervention, had previously been used to produce antibodies to ebola and even coronavirus-like particles to be used in covid vaccines. In the laboratory, the group designed new DNA sequences, i.e. pieces of genetic code to mimic the moth’s genes, and introduced some molecular switches to fine-tune their expression, which effectively turns the production process on and off. “An important component of the new research has been the ability to fine-tune pheromone production, as forcing plants to continually build these molecules has its drawbacks,” the statement said. It is clear: by leading an organism to tasks that do not belong to it, energy is diverted from its normal growth and development.

“Plants produce a lot of pheromones, but they are unable to grow much, which substantially reduces the capacity of our production line,” Patron added. “Our new research provides a way to regulate gene expression with much more precision.” . All this thanks to the tests conducted in the laboratory with which scientists have managed to perfect, for example thanks to the copper sulfatethe control of genes responsible for producing the mix of specific molecules that mimic the sex pheromones of moth species, including the orange navel worm and the cotton nocturnal. Copper sulfate is widely used in agriculture but it is too pollutant, both in production and in the persistence in the environment for crops, and this obviously remains a controversial aspect of a technique which in any case would drastically reduce the use of further pesticides and above all would allow the production of artificial pheromones in a less impactful way. Because that’s the basic idea.

Scientists were even able to carefully control the production of different components of the pheromones, allowing them to tweak the formula to better suit specific moth species. “We have shown that we can control the expression levels of each gene against the others – added the research manager – this allows us to control the relationship between the products made. Getting the right recipe is particularly important for moth pheromones as they are often a mixture of two or three molecules in specific proportions. Our collaborators in Spain are now extracting the plant-derived pheromones and testing them in dispensers to see how they compare in the fields with moths.”

The aim of the research, part of the Susphire Project supported by ERACoBiotech, Horizon 2020 and the UKRI Biotechnology and Biological Sciences Research Council, is certainly not to engineer every crop but produce pheromones more sustainably: the team hopes that the work paves the way for the habitual use of plants to produce a wide range of valuable natural products: ‘It is much more expensive to build complex molecules using chemical processes – concluded Patron – plants already produce a number of useful molecules, so we are able to use the latest techniques to adapt and refine existing genetic mechanisms. In the future, we may see greenhouses full of plant factories and implement a more environmentally friendly, economical and sustainable way to produce complex molecules.”