Genomes of trombidid mites reveal novel predicted allergens and laterally transferred genes associated with secondary metabolism

Abstract

BackgroundTrombidid mites have a unique life cycle in which only the larval stage is ectoparasitic. In the superfamily Trombiculoidea (“chiggers”), the larvae feed preferentially on vertebrates, including humans. Species in the genus Leptotrombidium are vectors of a potentially fatal bacterial infection, scrub typhus, that affects 1 million people annually. Moreover, chiggers can cause pruritic dermatitis (trombiculiasis) in humans and domesticated animals. In the Trombidioidea (velvet mites), the larvae feed on other arthropods and are potential biological control agents for agricultural pests. Here, we present the first trombidid mites genomes, obtained both for a chigger, Leptotrombidium deliense, and for a velvet mite, Dinothrombium tinctorium.ResultsSequencing was performed using Illumina technology. A 180 Mb draft assembly for D. tinctorium was generated from two paired-end and one mate-pair library using a single adult specimen. For L. deliense, a lower-coverage draft assembly (117 Mb) was obtained using pooled, engorged larvae with a single paired-end library. Remarkably, both genomes exhibited evidence of ancient lateral gene transfer from soil-derived bacteria or fungi. The transferred genes confer functions that are rare in animals, including terpene and carotenoid synthesis. Thirty-seven allergenic protein families were predicted in the L. deliense genome, of which nine were unique. Preliminary proteomic analyses identified several of these putative allergens in larvae.ConclusionsTrombidid mite genomes appear to be more dynamic than those of other acariform mites. A priority for future research is to determine the biological function of terpene synthesis in this taxon and its potential for exploitation in disease control.

Ecological and microbiological diversity of chigger mites, including vectors of scrub typhus, on small mammals across stratified habitats in Thailand

“…We therefore hypothesized that chigger species richness may be a driver of scrub typhus incidence across the whole country, perhaps by facilitating recombination between O. tsutsugamushi strains [14]. In addition, since the chigger genome has been shaped by contact with soil microorganisms [11], we tested the hypothesis that the chigger microbiome is strongly influenced by local habitat type. This is important, as in other arthropod vectors, intracellular bacterial symbionts and gut microbiota are known to have significant impacts on vector competence [15][16][17].…”

Extracting the invisible: obtaining high quality DNA is a challenging task in small arthropods

“…Nevertheless, factors like costs or preparation time were not considered (Gamba et al, 2016). In general, commercial extraction kits were used for gDNA extraction in varying NGS approaches of minute arthropods, as copepods (Blanco-Bercial & Bucklin, 2016), microhymenoptera (Cruaud et al, 2018) and also mites (Dong et al, 2018; Edwards et al, 2018; Esteban et al, 2018; Lee & Wang, 2016; Schäffer et al, 2018; Techer et al, 2019).…”

Aquatic Hemiptera in Southwest Cameroon: Biodiversity of Potential Reservoirs of Mycobacterium ulcerans and Multiple Wolbachia Sequence Types Revealed by Metagenomics

“…Gene rearrangement analysis of the assembled mitogenomes were visualized using the Mauve genome aligner v. 25 February 2015 [88]. MrBayes v. 3.2.6 [89] was run with the generation parameter set to '1 in 100 samples' and the substitution model set to 'GTR + G + I' (the first 25% of samples were discarded as burn-in) to build a mitogenome tree based on protein superalignments, as previously described [90]. The assembled mitogenomes were submitted to NCBI under accession numbers MN027271-MN027279.…”