10-12 April 2019: The OECD Conference on RNAi based pesticides provided an overview on the current status and future possibilities for the regulation of externally applied dsRNA-based products that are proposed for use as pesticides. The event facilitated exchanges between policy makers, academia, industry on their implications in health, environment, and regulation.
CCXG global forum, April 2024, Marta Torres-Gunfaus
RNAi as a novel technology in pest control: current status and challenges - Olivier Christiaens, Ghent University, Belgium
1. RNAi as a novel technology in
pest control: current status and
challenges
Olivier Christiaens
2. Introduction to RNAi
What is RNA Interference (RNAi)?
• Post-transcriptional gene
silencing
Gene silencing
• mRNA degradation to prevent
formation of protein
3. Cellular functions:
• Protection against viruses (siRNA)
• Protection against ‘jumping genes’ (piRNA)
• Internal gene regulation (miRNA)
4. RNAi as a pest control technology
Joga et al., 2016; Frontiers in Physiology
8. RNAi as a crop protection technology
Protection of beneficial insects against viruses and parasites
Deformed wing virus
(DWV)
DWV-dsRNA
DWV-dsRNA is mixed with food
Virus infection
• Desai et al 2012 (Insect Mol Biol vol 21)
• Varroa destructor control (Monsanto/Bayer)
9. Efficiency of RNAi in arthropods:
• Very variable
Coleoptera > Diptera, Hemiptera > Lepidoptera
Factors affecting RNAi sensitivity
• Degradation of dsRNA (saliva, gut, haemolymph)
• Uptake of dsRNA in cells (Sid-like channels and/or endocytosis)
• Endosomal release in the cell
• Spreading and amplification of RNAi signal (no RdRP in insects)
• Virus infections (saturation or VSPs)
RNAi as a crop protection technology
10. Not all Coleoptera are highly sensitive…
RNAi efficiency
Cylas (African sweet potato weevil)
• Much lower sensitivity upon ingestion
of high amounts of dsRNA
• Very high sensitivity with injection
• High silencing efficiency
• Silencing lasts up to 10 days after
single injection
Adult-
control
(dsGFP)
Adult (dsLac2)
Prentice et al., 2015
11. RNAi efficiency
Oral delivery of dsRNA in Cylas
C. puncticollis C. brunneus
C C 3h 5’ 15’ 30’ 1h 2h 3h C C 3h 5’ 15’ 30’ 1h 2h 3h
5’ 15’ 30’ 1h
+ 20mM EDTA
5’ 15’ 30’ 1h 3h 16h
L. decemlineata
Prentice et al., 2016, Pest Management Science
Christiaens et al., 2016, Scientific Reports
13. dsRNA delivery
• Host-induced gene silencing
Constant dsRNA exposure, long term control
No spraying necessary
dsRNA mostly diced to siRNA by plant siRNA machinery
Regulation, cost, public acceptance
22. Polymers
• Spodoptera exigua
• Low sensitivity for RNAi
• Rapid nucleolytic degradation of dsRNA
in the digestive system
• Very alkaline gut lumen
Topical dsRNA delivery
25. Environmental safety
• RNAi-mediated crop protection
Biopesticide (?)
Molecule ubiquitously present in nature
Sequence-dependent mode of action (potential for selectivity)
Short persistence in the environment
However…adverse effects on non-target (insect) species are
possible
Sequence-dependent effects dsRNA design is critical
Sequence-independent effects
26. Literature review of baseline information to support the risk assessment of RNAi-derived GM plants
Cellular uptake and systemic spread of sRNAs
Plausible routes of exposure
RNAi efficiency and factors that influence this
Plausibility of unintended effects
Overview of available genomic data in invertebrate species and a
discussion on the potential role of bioinformatics in RNAi ERA
27. Thank you for your attention!
Dr. ir. Olivier Christiaens
Department of Plants and Crops
Ghent University – Belgium
olchrist.christiaens@ugent.be