Functional characterization of voltage-gated sodium channels in two mirid pests and identification of kdr mutations in pyrethroid resistant Lygus lineolaris population

Authors: Du, Yuzhe; Scheibener, Shane; Zhu, Yu Cheng; Perera, Omaththage; Reddy, Gadi; ZHOROV, BORIS - Department Of Biochemistry And Microbiology, University Of Zululand

Submitted to: Insect Biochemistry and Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2026
Publication Date: 1/5/2026
Citation: Du, Y., Scheibener, S.A., Zhu, Y., Perera, O.P., Reddy, G.V., Zhorov, B.S. 2026. Functional characterization of voltage-gated sodium channels in two mirid pests and identification of kdr mutations in pyrethroid resistant Lygus lineolaris population. Insect Biochemistry and Molecular Biology. 188(104486):1-14. https://doi.org/10.1016/j.ibmb.2026.104486.
DOI: https://doi.org/10.1016/j.ibmb.2026.104486

Interpretive Summary: Lygus lineolaris (tarnished plant bug) and Lygus hesperus (western tarnished plant bug) are two major pests that inflict significant damage on fruits, cotton, and vegetables across the United States. Historically, farmers have relied heavily on pyrethroid insecticides to manage these pests. However, over time, both species have developed resistance, making control efforts increasingly difficult and costly.Our study investigated the molecular mechanisms underlying this resistance. Pyrethroids target sodium channels in insect nerve cells—proteins essential for generating electrical signals in the nervous system. We examined the genetic composition of these sodium channels in both susceptible (non-resistant) and resistant populations of Lygus bugs.We found that these insects produce multiple variants of sodium channels due to natural variation in gene expression. Some variants generate stronger nerve signals than others, potentially influencing how the insects respond to insecticides. Additionally, we identified specific mutations in the sodium channel genes of resistant L. lineolaris populations. These mutations, previously associated with pyrethroid resistance in other insect species, are now confirmed in field populations of tarnished plant bugs for the first time.

Technical Abstract: Lygus lineolaris and Lygus hesperus are economically important pests that cause substantial damage to a wide range of fruit, fiber, and vegetable crops in the United States. Extensive use of pyrethroid insecticides for their control has led to the development of resistance, primarily driven by enhanced metabolic detoxification, as previously documented in resistant populations.Voltage-gated sodium channels (Navs), the primary molecular targets of pyrethroids, are essential for initiating and propagating action potentials in insect neurons. In this study, we isolated 17 full-length Nav cDNA clones encoding 14 unique splicing variants from a susceptible strain of L. hesperus (sLhNav), two variants from a susceptible L. lineolaris strain (sLlNav), and eight full-length clones encoding seven variants from a pyrethroid-resistant L. lineolaris population (rLlNav), based on the usage of 12 alternative exons.Functional expression in Xenopus oocytes revealed that nine sLhNav and two sLlNav variants produced sodium currents suitable for electrophysiological analysis, each displaying distinct gating properties. Notably, Nav variants lacking exon b generated significantly larger currents compared to those including exon b.We also identified A-to-I RNA editing events in both Lygus Navs. A key finding was the identification of three knockdown resistance (kdr) mutations in eight rLlNav variants: L1023F/S in segment IIS6 and L934I in the IIS4–S5 linker (corresponding to L1014F, L1014S, and L925I in the housefly Nav). These mutations have been previously associated with pyrethroid resistance in other insect species, and this is the first report of their presence in field-collected, resistant L. lineolaris populations.Together with earlier reports of enhanced metabolic detoxification, our findings support a dual resistance strategy in L. lineolaris, involving both target-site insensitivity and elevated detoxification enzyme activity. The comprehensive characterization of sodium channel variants in L. hesperus (sLhNav) and L. lineolaris (sLlNav and rLlNav), along with the identification of L1023F/S and L934I mutations, provides valuable insight into Nav diversity in Lygus species and the molecular basis of pyrethroid resistance in L. lineolaris.These findings have important implications for the development of next-generation pyrethroids with improved efficacy, selectivity, and resistance management potential.