Biology subjects

Berenbaum, M. R.

Publications and source records attributed to Berenbaum, M. R..

2 recordsLinked to original sources

bioRxiv2026

Molecular and functional characterization of CYP6AN1 orthologs involved in capsaicin metabolism in two Helicoverpa species

The generalist Helicoverpa armigera and the specialist Helicoverpa assulta are closely related noctuid pests and are among the few insect herbivores capable of feeding on and damaging hot pepper fruits, which contain the defensive compound capsaicin. Cytochrome P450 monooxygenases (P450s) contribute to the metabolism of plant defensive compounds and can facilitate insect adaptation to chemically defended host plants. Here, we identified CYP6AN1 in H. assulta (HassCYP6AN1) and comparatively characterized the CYP6AN1 orthologs from H. armigera (HarmCYP6AN1) and H. assulta. RACE identified one full-length HarmCYP6AN1 transcript and three full-length HassCYP6AN1 transcript isoforms. The HassCYP6AN1 isoforms contained distinct 5' UTRs generated by alternative transcription initiation and splicing but shared an identical coding sequence. Sequence comparisons and phylogenetic analysis supported their assignment as orthologs. Constitutive CYP6AN1 expression was higher in the H. assulta midgut, whereas dietary capsaicin significantly induced CYP6AN1 expression in the H. armigera midgut. Recombinant CYP6AN1 proteins were co-expressed with NADPH-cytochrome P450 reductase in Escherichia coli, and their substrate-metabolizing activities were evaluated using HPLC-based depletion assays. Both orthologs metabolized capsaicin, but HarmCYP6AN1 exhibited an approximately 2.3-fold higher depletion activity than HassCYP6AN1 under the conditions tested. HarmCYP6AN1 also showed P450-content-dependent xanthotoxin depletion, whereas no detectable xanthotoxin metabolism was observed for HassCYP6AN1. These findings establish CYP6AN1 as a component of the capsaicin-metabolizing repertoire of both species and reveal substantial divergence between the orthologs in transcript organization, expression regulation, catalytic activity, and detectable substrate range.

zoology↗

bioRxiv2019

Selective sweeps in a nutshell; the genomic footprint of rapid insecticide resistance evolution in a major insect pest of tree nuts

Relatively few genome-wide population studies of field-acquired insecticide resistance have been carried out on agricultural pests. Recently acquired bifenthrin resistance in a population of the navel orangeworm (Amyelois transitella), the main insect pest of almond orchards in California, provided an opportunity to examine the short- and long-term effects of heavy insecticide usage in the population genomic landscape of this species. We re-sequenced the genomes of three contemporary A. transitella natural populations differing in bifenthrin resistance status and characterized their population genetics parameters, in the process we detected an exceptionally large selective sweep in all populations. This sweep has virtually no polymorphisms and extends up to 1.3 Mb (spanning 43 genes) in the resistant population. We analyzed the possible causes of this unusually strong population genetic signature, and found genes in the sweep that are associated with DDT and pyrethroid resistance including a cluster of cytochrome P450 coding genes and the gene coding for the small conductance sodium channel "para". Moreover, we found that the sequence along the sweep is nearly identical in the genome assembled from a strain founded in 1966, suggesting that the underpinning for insecticide resistance may have been laid a half-century ago when the California Central Valley experienced massive area-wide applications of DDT for pest control. Our findings are consistent with a scenario whereby insecticide resistance in this species evolved as a stacking of selective pressures that started decades ago and that effectively reduced variation in a region of the genome containing several genes associated with resistance to insecticides with a shared target site and mechanism of action.

genomics↗