Rewired RNAi-mediated genome surveillance in house dust mites

Abstract

House dust mites are common pests with an unusual evolutionary history, being descendants of a parasitic ancestor. Transition to parasitism is frequently accompanied by genome rearrangements, possibly to accommodate the genetic change needed to access new ecology. Transposable element (TE) activity is a source of genomic instability that can trigger large-scale genomic alterations. Eukaryotes have multiple transposon control mechanisms, one of which is RNA interference (RNAi). Investigation of the dust mite genome failed to identify a major RNAi pathway: the Piwi-associated RNA (piRNA) pathway, which has been replaced by a novel small-interfering RNA (siRNA)-like pathway. Co-opting of piRNA function by dust mite siRNAs is extensive, including establishment of TE control master loci that produce siRNAs. Interestingly, other members of the Acari have piRNAs indicating loss of this mechanism in dust mites is a recent event. Flux of RNAi-mediated control of TEs highlights the unusual arc of dust mite evolution.

Beyond insects: current status and achievements of RNA interference in mite pests and future perspectives

“…In the nematode Caenorhabditis elegans , RdRp proteins are required for the amplification of silencing triggers, while no RdRP homologs have been identified in insects. Intriguingly, five clear RdRp homologs have been found in the genome of T. urticae and eight have been discovered in the American house dust mite Dermatophagoides farinae . Indeed, the presence of RdRp genes in mites is very intriguing as they are not present in insects, although the presence of these homologous RdRp genes in mites does not necessarily mean that they have a role in systemic transmission of RNAi.…”

“…Intriguingly, five clear RdRp homologs have been found in the genome of T. urticae and eight have been discovered in the American house dust mite Dermatophagoides farinae. 35,37 Indeed, the presence of RdRp genes in mites is very intriguing as they are not present in insects, although the presence of these homologous RdRp genes in mites does not necessarily mean that they have a role in systemic transmission of RNAi. In dust mites, the RRF1/EGO1 RdRp genes, which are responsible for siRNA production in C. elegans, lack the proline/tryptophan-rich loop typically seen in C. elegans homologs.…”

“…35 Homologs of core RNAi machinery genes (including miRNA, siRNA and piRNA) such as Dicer (two genes), Pasha (two genes), Drosha (one gene), Loquacious (two genes), Argonaute (Ago) (seven genes), Piwi/Aubergine (Aub)/Ago3 (seven genes) and RNA-dependent RNA polymerase (RdRp) (five genes) were found in the genome of T. urticae. In addition, various RNAi factors have also been reported in other mite and tick species 10,36,37 and RNAi in ticks has been reviewed. 38 It seems evident that there is an expansion of Ago genes and the presence of RdRp genes in various mite species, suggesting a different selection pressure or evolutionary path in the RNAi pathway in comparison with insects.…”

Movement of small RNAs in and between plants and fungi

“…siRNA, miRNA as well as piRNA all act to control gene expression and play important roles in many fundamental biological processes in eukaryotic organisms. They have been tied to vital processes such as cell growth, tissue differentiation, heterochromatin formation, cell proliferation, and disease resistance (Blair and Olson, ; Yuan et al , ; Tassetto et al , ; Czech et al , ; Mondal et al , ; Almeida et al , ). Research over the past few decades has led to powerful insight into the structure and function of small RNAs, which has been summarized in several reviews (Eamens et al , ; Ghildiyal and Zamore, ; Peters and Meister, ; Pratt and MacRae, ; Holoch and Moazed, ; Quinn and Chang, ; Zhang, Cozen et al , ; Zhang et al , ).…”

Multiple doses of adipose tissue-derived mesenchymal stromal cells induce immunosuppression in experimental asthma

“…HDM is present in almost all environments and is the most common allergen implicated in the onset of human asthma, affecting approximately 85% of asthmatic patients globally . In experimental models, HDM closely reproduces several hallmark features of human disease, including the inflammatory process with Th2 and eosinophilic responses and remodeling of both airways and lung parenchyma .…”