RNA interference biopesticide using engineered E. coli HT115 for sugarcane aphid management in sorghum

Overview

This research proposes an affordable RNA interference (RNAi)-based biopesticide to manage the sugarcane aphid (SCA) in sorghum. The approach uses a recombinant E. coli strain HT115 engineered to produce double-stranded RNA (dsRNA) molecules that target essential genes in the sugarcane aphid, specifically acetylcholinesterase (AChE), the target site of organophosphate insecticides, and the nicotinic acetylcholine receptor (nAChR), the target of neonicotinoid insecticides. By silencing these critical genes through RNAi, the bacteria deliver a lethal molecular payload to the pest when applied to crops. This method offers a targeted, biologically based alternative to conventional chemical insecticides, potentially reducing production costs for sorghum growers while addressing pest resistance concerns.

Technical specifications

Key features:

• Engineered E. coli HT115 bacteria producing dsRNA targeting SCA AChE and nAChR genes
• RNA interference mechanism that suppresses essential pest genes, reducing reproduction and causing mortality
• Laboratory bioassays demonstrated 2.3- to 2.9-fold reduction in reproducing SCA individuals compared to controls
• Effective dose identified at 200 ng/ml dsRNA in initial validation studies
• Application method: bacteria suspended in MES solution and sprayed onto leaf discs or sorghum plants
• Dose range testing: 10^4 to 10^8 cells per application
• Additional demonstrated capability: dsRNA expression targeting Armillaria CYP51 gene reduced fungal growth after 18 days of co-culture
• Greenhouse validation planned to assess 28-day treatment efficacy

Technology readiness level

The technology is currently at an early-to-mid stage of development. Initial proof-of-concept has been completed under an industry seed grant, with dsRNAs targeting two sites in the SCA AChE gene successfully developed and tested in laboratory bioassays, demonstrating significant reduction in aphid reproduction. Future validation steps include expanded laboratory bioassays to determine dose-response curves and mortality rates at multiple bacterial concentrations over 120 hours, gene suppression analysis at 72 hours, and greenhouse trials to evaluate treatment efficacy over a 28-day period. Additional funding is being sought to support wage costs and consumables for these validation studies.