Abstract
Pesticide-resistant populations of the predatory mite Metaseiulus (= Typhlodromus or Galendromus) occidentalis (Arthropoda: Chelicerata: Acari: Phytoseiidae) have been used in the biological control of pest mites such as phytophagous Tetranychus urticae. However, the pesticide resistance mechanisms in M. occidentalis remain largely unknown. In other arthropods, members of the glutathione-S-transferase (GST), cytochrome P450 (CYP) and carboxyl/cholinesterase (CCE) gene superfamilies are involved in the diverse biological pathways such as the metabolism of xenobiotics (e.g. pesticides) in addition to hormonal and chemosensory processes. In the current study, we report the identification and initial characterization of 123 genes in the GST, CYP and CCE superfamilies in the recently sequenced M. occidentalis genome. The gene count represents a reduction of 35% compared to T. urticae. The distribution of genes in the GST and CCE superfamilies in M. occidentalis differs significantly from those of insects and resembles that of T. urticae. Specifically, we report the presence of the Mu class GSTs, and the J’ and J” clade CCEs that, within the Arthropoda, appear unique to Acari. Interestingly, the majority of CCEs in the J’ and J” clades contain a catalytic triad, suggesting that they are catalytically active. They likely represent two Acari-specific CCE clades that may participate in detoxification of xenobiotics. The current study of genes in these superfamilies provides preliminary insights into the potential molecular components that may be involved in pesticide metabolism as well as hormonal/chemosensory processes in the agriculturally important M. occidentalis.
Highlights
The predatory mite Metaseiulus (= Typhlodromus or Galendromus) occidentalis (Arthropoda: Chelicerata: Arachnida: Acari: Parasitiformes: Phytoseiidae) is an important natural enemy of agricultural pests such as plant-feeding mites in the families Tetranychidae, Tarsonemidae, PLOS ONE | DOI:10.1371/journal.pone.0160009 July 28, 2016GST, cytochrome P450 (CYP) and CCE Superfamilies in Mite Metaseiulus occidentalisEriophyidae and Tenuipalpidae in the USA, Australia, and New Zealand [1,2,3,4,5,6]
Pesticide-resistant strains of M. occidentalis have been developed through laboratory selection and these genetically improved mites have been used in biological control programs [7,8,9]
Based on the results of the phylogenetic analyses, we report that M. occidentalis and T. urticae share similar patterns of gene distribution in the GST and CCE, and, to a lesser extent, the CYP superfamilies
Summary
The predatory mite Metaseiulus (= Typhlodromus or Galendromus) occidentalis (Arthropoda: Chelicerata: Arachnida: Acari: Parasitiformes: Phytoseiidae) is an important natural enemy of agricultural pests such as plant-feeding mites in the families Tetranychidae, Tarsonemidae, PLOS ONE | DOI:10.1371/journal.pone.0160009 July 28, 2016GST, CYP and CCE Superfamilies in Mite Metaseiulus occidentalisEriophyidae and Tenuipalpidae in the USA, Australia, and New Zealand [1,2,3,4,5,6]. Pesticide-resistant (carbaryl, organophosphate, and sulfur) strains of M. occidentalis have been developed through laboratory selection and these genetically improved mites have been used in biological control programs [7,8,9]. Carbamates and OPs inhibit AChE activities in arthropods, disrupting nerve impulses, killing these animals or interfering with their ability to carry out normal functions [14]. Arthropod strains resistant to carbamates and OPs may carry an AChE with point mutations (i.e. toxicodynamic changes) that make it less sensitive to these pesticides [10, 12, 15,16,17,18,19,20,21]. Increased tolerance to OPs can be achieved by elevating the expression of AChE through gene duplication, such as the cases in some resistant strains of T. urticae [22, 23]
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