Scientists sequence small genome of a pest: spider mite

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Friday, November 25, 2011

A spider mite, roughly 0.5mm long
Image: Giles San Martin.

A team of 55 researchers led by University of Western Ontario biologist Miodrag Grbic has sequenced the genome of the spider mite Tetranychus urticae, a pest that costs over USD 1 billion to control annually. Their results were published in the journal Nature yesterday. The genome is the smallest arthropod genome sequenced so far.

The study was funded by the US Depeartment of Energy Joint Genome Institute programme, Genome Canada, and the European Union.

The pest is resistant to major plant toxins, and it takes a spider mite from two to four years to become resistant to new pesticides. University of Utah assistant professor of biology Richard M. Clark, a study co-author, said, "One key thing that makes spider mites unique is they can eat many, many different plant species... These mites are ... a major cause of people's house plants turning yellow and getting sick. They also are a major problem for agricultural nurseries and greenhouses, and for field crops. ... [the spider mite] has been found to rapidly develop resistance to multiple types of pesticides, often within a couple of years after a pesticide is introduced."

The study found the mite's genome includes a variety of genes responsible for digestion and toxin degradation, possibly including some genes from bacteria and fungi. Because these bacterial/fungal genes are peculiar to spider mites, they appear to be a rare example of lateral gene transfer — gene transfer between distant species.

The study also found 17 web-production genes. The spider mite's webs provide weather- and predator-protection and are somewhat stronger than webs of other species.