Dramatically dynamic genomic evolution of a mighty mite

March 10, 2016
Dramatically dynamic genomic evolution of a mighty mite
Female Metaseiulus occidentalis, Credit: Aaron Pomerantz

Sequencing and comparative analysis of the genome of the Western Orchard predatory mite has revealed intriguingly-extreme genomic evolutionary dynamics through an international research effort co-led by scientists from the University of Geneva and the SIB Swiss Institute of Bioinformatics. In a study published in the journal Genome Biology and Evolution, the researchers detail the initial insights into several remarkable features of the genome of this agriculturally important mite that is widely employed to control plant pests, with thousands shipped to fruit growers every day.

As a major natural enemy of several damaging agricultural pests, the predatory mite Metaseiulus occidentalis is used in many agricultural settings as an effective biological control agent. Some of its favourite prey include spider mites that feed on and destroy various fruits including strawberries, apples, peaches and grapes. "I have been studying the behaviour, ecology, and molecular biology of these mites for more than 40 years," said Prof. Marjorie Hoy lead author from the University of Florida USA, "so I was very keen to sequence the to reveal the full catalogue of ." To explore the unique biology of this agriculturally important predator the researchers focused their studies on genes putatively involved in processes linked to paralysis and pre-oral digestion of prey species and its rather rare parahaploid sex determination system, as well as how it senses chemical cues from its surroundings and defends itself from infections.

Compared with other arthropod species, the evolutionary history of this mite's has been particularly dynamic. For example, the team's analyses revealed remarkably more intron gains and losses than in other arthropods. "The dynamic gains and losses of introns in the genes of this mite are in stark contrast to its closest relative with a draft genome assembly, the Ixodes tick" described Dr Robert Waterhouse, lead author from the University of Geneva and the SIB Swiss Institute of Bioinformatics. They identified five copies of Dicer-2, a gene found almost exclusively in single-copy in other arthropods, suggesting a possible rewiring of RNA processing pathways. The Hox genes, which are important for determining animal body plans and are located in a cluster of neighbouring genes in almost all species examined to date, were found to be completely dispersed across the mite's genome. "This raises questions about how regulatory programmes that turn Hox genes on and off during the coordinated development of complex body plans can be achieved even when the genes are no longer physically close to each other in the genome" explained Dr Waterhouse.

"These resources greatly improve the genomic sampling of chelicerates, a group of arthropods that has so far been poorly represented mainly due to challenges associated with their often very large genomes" said Prof. Stephen Richards from the Baylor College of Medicine USA, where the genome sequencing was performed. Indeed, results from the study's phylogenomic analyses question the relationships amongst some of the major chelicerate groups of mites, ticks, and spiders, further emphasising the need for improved genomic sampling in this clade. This reference genome assembly therefore provides valuable new high-quality resources for future functional genomic and taxonomic analyses of this family of predatory mites and other arachnids.

Explore further: Raw material for new genes

More information: Marjorie A. Hoy et al. Genome sequencing of the phytoseiid predatory mite reveals completely atomised genes and super-dynamic intron evolution , Genome Biology and Evolution (2016). DOI: 10.1093/gbe/evw048

Related Stories

Raw material for new genes

March 8, 2016

Every region of DNA codes for a gene. Well, not quite. Although an organism's genome contains some regions that are read and transcribed into RNA, many of those do not give rise to functional genes. Scientists at the Max ...

New genes born by accident lead to evolutionary innovation

December 31, 2015

Novel genes are continuously emerging during evolution, but what drives this process? A new study, published in PLOS Genetics, has found that the fortuitous appearance of certain combinations of elements in the genome can ...

Recommended for you

Study shows how giraffe assassin bugs outwit spider prey

October 26, 2016

(Phys.org)—A biologist at Macquarie University in Australia has discovered the secret behind the giraffe assassin's ability to catch and kill spiders in their webs. In his paper published on the open access site Royal Society ...

New analysis of big data sheds light on cell functions

October 26, 2016

Researchers have developed a new way of obtaining useful information from big data in biology to better understand—and predict—what goes on inside a cell. Using genome-scale models, researchers were able to integrate ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.