title: Identification and characterization of an esterase involved in malathion resistance in the head louse Pediculus humanus capitis.
abstract: Enhanced malathion carboxylesterase (MCE) activity was previously reported to be involved in malathion resistance in the head louse Pediculus humanus capitis (Gao et al., 2006 [8]). To identify MCE, the transcriptional profiles of all five esterases that had been annotated to be catalytically active were determined and compared between the malathion-resistant (BR-HL) and malathion-susceptible (KR-HL) strains of head lice. An esterase gene, designated HLCbE3, exhibited approximately 5.4-fold higher transcription levels, whereas remaining four esterases did not exhibit a significant increase in their transcription in BR-HL, indicating that HLCbE3 may be the putative MCE. Comparison of the entire cDNA sequences of HLCbE3 revealed no sequence differences between the BR-HL and KR-HL strains and suggested that no single nucleotide polymorphism is associated with enhanced MCE activity. Two copies of the HLCbE3 gene were observed in BR-HL, implying that the over-transcription of HLCbE3 is due to the combination of a gene duplication and up-regulated transcription. Knockdown of HLCbE3 expression by RNA interference in the BR-HL strain led to increases in malathion susceptibility, confirming the identity of HLCbE3 as a MCE responsible for malathion resistance in the head louse. Phylogenetic analysis suggested that HLCbE3 is a typical dietary esterase and belongs to a clade containing various MCEs involved in malathion resistance.
authors: Research Institute for Agriculture and Life Sciences, Seoul National University, 151-921, Republic of Korea.
authors: Deok Ho
authors: DH
authors: Kwon
authors: Department of Agricultural Biotechnology, Seoul National University, 151-921, Republic of Korea.
authors: Ju Hyeon
authors: JH
authors: Kim
authors: Research Institute for Agriculture and Life Sciences, Seoul National University, 151-921, Republic of Korea.
authors: Young Ho
authors: YH
authors: Kim
authors: Department of Veterinary and Animal Science, University of Massachusetts, Amherst, MA 01003, USA.
authors: Kyong Sup
authors: KS
authors: Yoon
authors: Department of Veterinary and Animal Science, University of Massachusetts, Amherst, MA 01003, USA.
authors: J Marshall
authors: JM
authors: Clark
authors: Research Institute for Agriculture and Life Sciences, Seoul National University, 151-921, Republic of Korea; Department of Agricultural Biotechnology, Seoul National University, 151-921, Republic of Korea. Electronic address: shlee22@snu.ac.kr.
authors: Si Hyeock
authors: SH
authors: Lee
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004950:Esterases / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D018628:Gene Dosage; D020440:Gene Duplication; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic; D019476:Insect Proteins / Q000235:genetics* / Q000378:metabolism; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology; D008294:Malathion / Q000494:pharmacology*; D008969:Molecular Sequence Data; D010374:Pediculus / Q000145:classification / Q000201:enzymology / Q000235:genetics*; D010802:Phylogeny; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
chemical_list: D019476:Insect Proteins; D007306:Insecticides; D004950:Esterases; D008294:Malathion
keywords: Carboxylesterase; Head lice; Malathion; Resistance