Transcriptomic investigation of the molecular mechanisms underlying resistance to the neonicotinoid thiamethoxam and the pyrethroid lambda-cyhalothrin in Euschistus heros (Hemiptera: Pentatomidae)

Abstract

Strains of Euschistus heros (Hemiptera: Pentatomidae) with resistance to thiamethoxam (NEO) and lambda-cyhalothrin (PYR), generated by selection with these insecticides in the laboratory, have been recently reported in Brazil. However, the mechanisms conferring resistance to these insecticides in E. heros remain unresolved. We utilized comparative transcriptome profiling and single nucleotide polymorphism (SNP) variant calling of susceptible and laboratory-selected resistant strains of E. heros to investigate the molecular mechanism(s) underlying resistance. The E. heros transcriptome was assembled using approximately 190.1 million paired-end reads, which generated 91,673 transcripts with a mean length of 720 bp and N50 of 1795 bp. Approximately, 54.8% of the assembled transcripts ware functionally annotated against the NCBI nr database, with most sequences (43%) being similar to the pentatomids Halyomorpha halys (43%) and Nezara viridula (29%). Comparative gene expression analysis between the susceptible (SUS) and NEO strains identified 215 significantly differentially expressed (DE) transcripts. DE transcripts associated with the metabolism of xenobiotics were all up-regulated in the NEO strain. The comparative analysis of the SUS and PYR strains identified 204 DE transcripts, including an esterase (esterase FE4), a glutathione-S-transferase, an ABC transporter (ABCC1), and aquaporins that were up-regulated in the PYR strain. We identified 9,588 and 15,043 non-synonymous SNPs in the PYR and NEO strains respectively in comparisons with the SUS strain. One of the variants (D70N) detected in the NEO strain occurs in a subunit (5) of the nicotinic acetylcholine receptor, the target-site of neonicotinoid insecticides. Nevertheless, the position of this residue was found very variable among 5 from insect species. In conclusion, neonicotinoid and pyrethroid resistance in laboratory-selected strains of E. heros is associated with a potential metabolic resistance mechanism mediated by the overexpression of several proteins commonly involved in the three phases of xenobiotic metabolism. Together these findings provide insight into the potential basis of resistance in E. heros and will inform the development and implementation of resistance management strategies against this important pest. HighlightsO_LI419 DE genes were observed in E. heros insecticide-resistant strains C_LIO_LI24,631 SNPs were identified in E. heros insecticide-resistant strains C_LIO_LIE. heros insecticide-resistant strains overexpress metabolic resistance genes C_LIO_LILambda-cyhalothrin-resistant E. heros overexpresses cuticular proteins C_LIO_LIThiamethoxam-resistant E. heros carries the target-site mutation D70N in nAChRalpha5 C_LI