Genomic insights into mite phylogeny, fitness, development, and reproduction

Abstract

BackgroundPredatory mites (Acari: Phytoseiidae) are the most important beneficial arthropods used in augmentative biological pest control of protected crops around the world. However, the genomes of mites are far less well understood than those of insects and the evolutionary relationships among mite and other chelicerate orders are contested, with the enigmatic origin of mites at one of the centres in discussion of the evolution of Arachnida.ResultsWe here report the 173 Mb nuclear genome (from 51.75 Gb pairs of Illumina reads) of the predatory mite, Neoseiulus cucumeris, a biocontrol agent against pests such as mites and thrips worldwide. We identified nearly 20.6 Mb (~ 11.93% of this genome) of repetitive sequences and annotated 18,735 protein-coding genes (a typical gene 2888 bp in size); the total length of protein-coding genes was about 50.55 Mb (29.2% of this assembly). About 37% (6981) of the genes are unique to N. cucumeris based on comparison with other arachnid genomes. Our phylogenomic analysis supported the monophyly of Acari, therefore rejecting the biphyletic origin of mites advocated by other studies based on limited gene fragments or few taxa in recent years. Our transcriptomic analyses of different life stages of N. cucumeris provide new insights into genes involved in its development. Putative genes involved in vitellogenesis, regulation of oviposition, sex determination, development of legs, signal perception, detoxification and stress-resistance, and innate immune systems are identified.ConclusionsOur genomics and developmental transcriptomics analyses of N. cucumeris provide invaluable resources for further research on the development, reproduction, and fitness of this economically important mite in particular and Arachnida in general.

Comparative analysis of mite genomes reveals positive selection for diet adaptation

“…1 ). The phylogenetic tree and time estimates of key nodes were consistent with those in recent studies 16 , 23 – 25 .

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Circulative Transmission of Cileviruses in Brevipalpus Mites May Involve the Paracellular Movement of Virions

“…TFPs display one or several domains consisting of 60-90 amino acids which have an β-structural core stabilized by a system of four invariant disulfide bonds. Proteins with similar structural characteristics have been found in the mite Tetranychus urticae and insects ( Grbić et al, 2011 ; Zhang et al, 2019 ). In flies, TFP-like proteins are involved in the formation of SJ adhesion structures, suggesting a common ancient role for these proteins in arthropods ( Hijazi et al, 2009 ).…”

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“…The advent of the high throughput sequencing used in Acari species facilitates our understanding of the molecular basis of predatory mite olfaction. We found striking variances among chemoreceptor families in Acariformes and Parasitiformes, including three phytoseiids M. occidentalis (Hoy et al 2016), Neoseiulus cucumeris (Zhang et al 2019a) and P. persimilis (Xu et al unpublished data) (Table 1).…”

“…In the absence of OBPs and ORs, odors perception may be achieved through other related proteins, such as Niemann-Pick Type C2 (NPC2), which was indicated as potential carriers for semiochemicals in chemical communication with GRs or IRs (Vizueta et al 2018;Li et al 2020). Although transient receptor potential (TRP) channels are involved in the process of heat and light perception (Hoy et al 2016;Peng et al 2016), they have also been implicated as chemosensory receptors (Ngoc et al 2016;Zhang et al 2019a). The olfactory lobes filled with glomerulus in P. persimilis play the same role as the antennal lobes in insects, due to only the first pedal nerve innervating the olfactory lobes (van Wijk et al 2006a).…”

“…In Neoseiulus barkeri, there are three NPC2 genes, which might be involved in responding and binding to female sex pheromone (Li et al 2020). Interestingly, a gene family involving in olfactory long-term memory formation in Drosophila, oo18 RNA-binding protein 2 (ORB2) genes, have been found in N. cucumeris with two members, suggesting the potential genetic basis of learning ability in predatory mites (Zhang et al 2019a). However, simple comparative analysis of genomic sequences does not allow inferring which specific members of already known chemosensory families are involved in which sensory modalities in Acari.…”