Transcriptome Analysis of Insecticide Resistance Mechanisms in Field Populations of the Bean Flower Thrips, Megalurothrips Usitatus (Bagnall)

Abstract

Introduction: The bean flower thrips, Megalurothrips usitatus (Bagnall), has inflicted significant damage on leguminous crops across the Asian tropics and established populations in North America. Numerous instances of ineffective pest control have been reported in various regions, raising concerns about potential food safety risks due to improper insecticide application.Objectives: To assess the status of insecticide susceptibility and the role of detoxification enzyme systems in M. usitatus.Methods: Resistance monitoring and detoxification enzyme activity assays were conducted. We utilized RNA-seq techniques and weighted gene co-expression network analysis (WGCNA) to validate the functions of key genes.Results: Resistance monitoring results revealed that the XW population exhibited resistance to five insecticides, with resistance ratios ranging from 7.17 to 42.90 compared to the indoor reference population (Lab-S). The NJ and YZ populations showed resistance to two and one insecticide, respectively, while the HP population exhibited the highest susceptibility. Elevated activities of P450, UGT, and AChE enzymes were observed in the YZ population. Correlation analysis indicated a positive relationship between the expression of three P450 genes and P450 activity. CarE activity was the highest in the XW population, with MusiPT_006325 positively correlated with CarE activity, while MusiPT_006095 and MusiPT_003750 showed negative correlations. GST activity was the highest in the HP population. WGCNA showed that the MEblue, MEturquoise, and MEbrown modules were positively correlated with the LC50 values of acetamiprid and novaluron but negatively correlated with the LC50 values of β-cypermethrin, spinetoram, emamectin benzoate, thiamethoxam, β-cypermethrin, and spirotetramat. Ten P450 genes and three UGT genes were identified as hub genes within these key modules.Conclusion: Our findings provide comprehensive overview of insecticide resistance and the role of detoxification enzymes in M. usitatus across four major Vigna unguiculata cultivation regions in China, offering valuable insights for the development of effective management strategies against this thrips species.

Keywords: Megalurothrips usitatus, Vigna unguiculata, insecticide resistance, detoxification enzymes, RNA-Seq, WGCNA