Yeast-based biopesticide could be future control method for PMPs

Colorado potato beetles are a menace to large-scale growers and backyard gardeners alike. Photo: EUGENE E. NELSON, BUGWOOD.ORG

A recent success in controlling the Colorado potato beetle (Leptinotarsa decemlineata, or CPB) using a novel yeast delivery technology for ribonucleic acid (RNA) leads Renaissance BioScience, a 10-year-old Canadian biotechnology company, to believe more research could find ways to use similar technology to control urban pests.

As the National Human Genome Research Institute defines it, RNA is a nucleic acid present in all living cells that has structural similarities to deoxyribonucleic acid (DNA), except that the sugar in RNA is ribose instead of deoxyribose and RNA uses the base uracil instead of thymine.
Numerous types of RNA are available. One of these, called RNA interference (RNAi), holds striking potential to help control the devastation wrought by agricultural and urban pests. As an environmentally friendly biopesticide, it can deliver targeted, precise mortality impacts to a specific insect.

RNA, DNA and proteins

Before explaining the relationship among DNA, RNA and proteins, it is important to note RNA is all around us. Along with DNA and proteins, RNA forms the basis of all living things and is found in everything we consume, from meat to vegetables. Without RNA, human life could not exist.

Dr. Erin Gilchrist

DNA stores all the information required for the development and function of any organism. More specifically, it stores instructions for making other large molecules called proteins. Messenger RNA (mRNA) plays a key role in turning the instructions held in DNA into functional proteins. Conversely, RNAi turns specific functions off by inhibiting the formation of proteins. It’s important to note RNAi does not create any new functions; it only turns off existing ones.

Using RNAi, it is possible to target the unique proteins essential to the life of a target pest. Once these genes that code for these essential proteins are switched off by the RNAi, the insect dies. Because these targeted genes are unique to each species, the RNAi has no negative effect on other insects, animals, humans or plants.

Reesha Parmar

Renaissance BioScience conducted the CPB study. Housed on the campus of the University of British Columbia in Vancouver, Renaissance BioScience focuses on engineering yeasts to meet a variety of vital food and industrial purposes — including acrylamide reduction, hydrogen sulfide prevention and, in this case, pest control. Renaissance’s RNAi bioactive yeast that is killed during manufacturing of the product is now a pest-targeting solution.

The dead yeast cannot reproduce or multiply but is consumed naturally by insects and animals. It can be used as an edible “suitcase” and vehicle to carry fragile RNAi bioactives safely into the gut of an insect, where it is digested to release the contained RNAi molecule to kill the pest. The dead yeast can withstand being dispersed into the environment in widely varying weather conditions. Plus, it can be produced cheaply and easily at scale.

Proof of concept: CPB

The first target pest of the yeast-based RNAi biopesticide, the notorious CPB, is an often pesticide-resistant scourge that has feasted on potato fields globally for decades. An independent benchtop evaluation of Renaissance’s biopesticide, conducted on CPB larvae that consume the potato plant leaves, revealed a 98.3 percent mortality rate and substantial reduction in plant damage. A key characteristic and industrial benefit of the yeast technology is its ability to incorporate many different gene targets at once and other biological RNAi enhancers to make the development of resistance much more difficult.

Recently, the Canadian government awarded approval for Renaissance to conduct research trials on its CPB RNAi biopesticide. The testing is slated to be carried out this year, and will include smaller-scale field trials in multiple other countries, with the objective of providing real-world proof of efficacy. In these trials, the company’s scientific team and collaborators will seek to determine the optimal use model for potato farmers, including identifying application rates and timing, ultimate insect mortality and overall crop protection attributes. The primary focus will be on maximizing the final tuber yield and quality as efficiently and cost-effectively as possible.

This field work is an important step forward in the company’s biopesticide development pipeline, and its results will help the team expand future field trials toward formal product registration. While focused on crop pests initially, Renaissance’s plans call for urban pest control development as well. It is currently seeking partnerships with other industry manufacturers to harness the yeast-based biopesticide for widespread use.