Kun Yan Zhu

RNA Interference in Insects
RNA interference (RNAi) has been known as common machinery for sequence-specific gene silencing through the RNAi pathway in eukaryotic organisms and has shown great promise as a novel approach for gene-specific insect pest management. However, there are significant differences in the efficiency of RNAi among different taxonomic groups of insects. For example, coleopterans have a robust RNAi response whereas lepidopterans often show a poor RNAi response. Such differences could be in part due to differences in the stability of double-stranded RNA (dsRNA) and in the efficiency of cellular uptake and endosomal escape of dsRNA among different insects. Dr. Zhu’s research program addresses questions related to the stability and cellular uptake of dsRNA in different insects. The relevant research focuses on the identification of candidate genes and the development of dsRNA delivery methods (e.g., dsRNA nanoparticle- and siRNA origami nanostructure-based approaches) for potential use in RNAi-based management of insect pests. This research has resulted in a U.S. patent and is expected to provide new insights into the mechanisms underlying differences in RNAi efficiency among insects, thereby helping researchers develop effective RNAi technologies for insect pest management.

Insecticide Detoxification and Resistance

The development of resistance to chemical insecticides and insecticidal molecules expressed in transgenic plants is one of the most significant challenges to effective insect pest management. Although genomic studies have identified numerous genes potentially involved in insecticide action, detoxification, and resistance, the functional roles of many of these genes in insecticide susceptibility and resistance remain poorly understood. Dr. Zhu’s research program focuses on elucidating the molecular mechanisms underlying insecticide detoxification and resistance through: (1) functional characterization of insecticide target genes, such as acetylcholinesterases; (2) investigation of the roles and regulation of detoxification genes, including cytochrome P450 monooxygenases, carboxylesterases, and glutathione S-transferases; and (3) molecular analysis of genes involved in the toxicity and resistance of insects to Bacillus thuringiensis (Bt) toxins. This research program provides insights into the molecular basis of insecticide resistance and contributes to the development of more effective strategies for insect pest control and resistance management.

Chitin Biosynthesis and Its Application to Pest Management

Chitin is the second most abundant biological polymer after cellulose and is an essential structural component of arthropods, including insects and spiders, as well as nematodes and fungi. In insects, chitin is synthesized primarily in epidermal and certain epithelial cells and is a vital component of the exoskeleton, tracheal cuticular linings, and peritrophic matrices. Despite decades of intensive research, many aspects of chitin formation, deposition, and regulation remain poorly understood. Dr. Zhu’s research program focuses on elucidating the molecular mechanisms underlying chitin biosynthesis and understanding how insecticides inhibit chitin synthesis in arthropods. This work provides new insights into the chitin biosynthetic pathway and the molecular basis of action of insecticides that target this pathway. Because chitin is essential in arthropods but absent from vertebrates, understanding its biosynthesis and inhibition may facilitate the development of selective, safe, and environmentally sustainable approaches to insect pest management.

Innovative Technologies for Insect Pest Management

Through collaborations with researchers from different disciplines at USDA-ARS, Dr. Zhu's research program also extends to the development of innovative technologies to improve the efficacy, precision, and practicality of insect pest management, particularly in stored-product and food-processing facilities. His collaborative research has included investigations of long-lasting insecticide-treated netting (LLIN) as a novel insecticide-delivery technology for managing stored-product insects, as well as aerosol applications to improve insecticide delivery and control. His research also explores semiochemical-based behavioral approaches, including the use of pheromones and other volatile cues for monitoring and managing stored-product pests. His research program also integrates molecular diagnostics with resistance monitoring and management, including the development and application of molecular assays for rapid detection of phosphine resistance in stored-product insects. By combining innovative insecticide-delivery systems with molecular tools for resistance monitoring, behavior-based approaches, his research contributes to more efficient, targeted, and sustainable pest-management strategies for protecting stored commodities.