Molecular cloning and sequence analysis of a novel P450 gene encoding CYP345D3 from the red flour beetle, Tribolium castaneum

Differential Expression of Cytochrome P450 CYP6 Genes in the Brown Marmorated Stink Bug, Halyomorpha halys (Hemiptera: Pentatomidae)

Cytochrome (CYP) P450s are a superfamily of enzymes that detoxify xenobiotics and regulate numerous physiological processes in insects. The genomes of phytophagous insects usually contain large numbers of P450s, especially within the CYP3 clan. Within this clan, CYP6 subfamily members help detoxify plant host secondary metabolites. In this study, we analyzed three CYP6 genes in the highly polyphagous invasive pest, Halyomorpha halys (Stål), commonly known as brown marmorated stink bug. We characterized and validated the expression of HhCYP6BQ27, HhCYP6BK13, and HhCYP6BK24 among sexes, tissues (gut, fat body, and Malpighian tubules) and hosts (apple, corn, soybean). Sequence characterization by amino acid alignments confirmed the presence of conserved motifs typical of the P450 superfamily. No significant differences existed in gene expression among sexes or when fed different hosts, suggesting that these transcripts might have broad substrate specificities. However, significant differences in gene expression were observed among the tissues studied and were gene-dependent. Collectively, the results show that H. halys differentially expressed CYP6 genes among tissues, which may be related to important and specific physiological functions. This study has increased our understanding of H. halys biology that can be useful for functional studies and can potentially be exploited in developing sustainable pest management strategies.

Molecular cloning and sequence analysis of novel cytochrome P450 cDNA fragments from Dastarcus helophoroides

The predatory beetle Dastarcus helophoroides (Fairmaire) (Coleoptera: Bothrideridae) is a natural enemy of many longhorned beetles and is mainly distributed in both China and Japan. To date, no research on D. helophoroides P450 enzymes has been reported. In our study, for the better understanding of P450 enzymes in D. helophoroides, 100 novel cDNA fragments encoding cytochrome P450 were amplified from the total RNA of adult D. helophoroides abdomens using five pairs of degenerate primers designed according to the conserved amino acid sequences of the CYP6 family genes in insects through RT-PCR. The obtained nucleotide sequences were 250 bp, 270 bp, and 420 bp in length depending on different primers. Ninety-six fragments were determined to represent CYP6 genes, mainly from CYP6BK, CYP6BQ, and CYP6BR subfamilies, and four fragments were determined to represent CYP9 genes. Twenty-two fragments, submitted to GenBank, were selected for further homologous analysis, which revealed that some fragments of different sizes might be parts of the same P450 gene.

Molecular cloning and characterization of a novel P450 gene encoding CYP6BK18 from Dastarcus helophoroides (Coleoptera: Bothrideridae)

A novel cDNA clone encoding a cytochrome P450 gene, named CYP6BK18 (GenBank KC683905), was isolated by reverse transcription PCR from Dastarcus helophoroides (Fairmaire) (Coleoptera: Bothrideridae), a natural enemy of beetles. The full-length cDNA sequence is 1,659 bp, containing a 1,533 bp open reading frame predicting a 510-amino acid protein possessing a transmembrane domain with a calculated molecular weight of 59.4 kDa and a theoretical pI of 8.94. The deduced amino acid sequence of CYP6BK18 showed a 59% identity with CYP6BK17 (GenBank XP_970481.1) from Tribolium castaneum. Phylogenetic analysis indicated that CYP6BK18 was most closely related to CYP6BK17 and CYP6BK14 (GenBank EFA05731.1) from T. castaneum. Expression patterns of CYP6BK18 in different tissues (head, oviduct, midgut, fat bodies, and Malpighian tubules), developmental stages (first- to sixth-instar larvae and adult) and 10 age groups of adult were analyzed by real-time quantitative PCR (RT-qPCR). The results showed that CYP6BK18 was highly expressed in adulthood. Also, RT-qPCR analysis among different age groups of adult showed that CYP6BK18 transcripts were abundant in the spawning period and peaked at the early stage of the adult development. Moreover, the tissue-specific expression levels of CYP6BK18 were in the order of midgut, Malpighian tubes and fatty body from high to low. These results suggest that cytochrome P450 CYP6BK18 may play a role in regulating the development and aging of D. helophoroides.

A review of control methods and resistance mechanisms in stored-product insects

This review describes the major stored-product insect species and their resistance to insecticides. The economic importance of the control of those pests is highlighted with a loss of more than one billion US dollars per year worldwide. A detailed common description of species resistance throughout the world has been developed, and we observed 28 recurrent studied species involved in resistance cases disseminated on the five continents. The different mechanisms, including behavioral resistance, were studied particularly on Oryzaephilus surinamensis. The role of detoxifying enzymes and studies on the genetic resistance, involving the kdr mutation mechanisms and the transmission of the genes of resistance, are also described. A chapter clarifying definitions on cross and multiple resistance is enclosed.

Molecular characterization of two novel deltamethrin-inducible P450 genes from Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae)

Two novel P450 genes, CYP6CE1 and CYP6CE2 (GenBank accession number: EF421245 and EF421246), were cloned and characterized from psocid, Liposcelis bostrychophila. CYP6CE1 and CYP6CE2 contain open reading frames of 1,581 and 1,563 nucleotides that encode 527 and 521 amino acid residues, respectively. The putative proteins of CYP6CE1 and CYP6CE2 show predicted molecular weights of 60.76 and 59.83 kDa with a theoretical pI of 8.58 and 8.78, respectively. CYP6CE1 and CYP6CE2 share 74% identity with each other, and the deduced proteins are typical microsomal P450s sharing signature sequences with other insect CYP6 P450s. Both CYP6CE1 and CYP6CE2 share the closest identities with Hodotermopsis sjoestedti CYP6AM1 at 48% among the published sequences. Phylogenetic analysis showed a closer relationship of CYP6CE1 and CYP6CE2 with CYP6 members of other insects than with those from other families. Quantitative real-time RT-PCR showed that both CYP6CE1 and CYP6CE2 are expressed at all developmental stages tested. Interestingly, CYP6CE2 transcripts decreased from the highest in 1st nymph to the lowest in adults, which seemed to suggest developmental regulation. However, neither CYP6CE1 nor CYP6CE2 were stage specific. The CYP6CE1 and CYP6CE2 transcripts in adults increased significantly after deltamethrin exposure. Recombinant protein expression studies are needed to determine the real functions of these proteins.