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Pires da Silva contributes to paper on spider mite genome

Spider mite(Image from www.insectimages.org)
Spider mite(Image from www.insectimages.org)

Andre Pires da Silva, an assistant professor of biology, is one of five principal investigators on a recent effort to map the genome of the two-spotted spider mite, or Tetranychus urticae, one of agriculture's most resilient and detrimental pests.

Pires da Silva, an evolutionary biologist, examined and interpreted the genome results to learn more about the spider mite's reproduction. He found that the genes involved in determining what sex offspring develop into are unlike any other known examples in genomics.

A paper on the project was published November 24 in the journal Nature. The lead author is Miodrag Grbić, a researcher at the University of Western Ontario. Pires da Silva is one of 55 co-authors, a group that includes scientists from Spain, Belgium, France, Portugal, Chile, Germany and Switzerland.

The sequencing represents the first complete Chelicerate genome. Chelicerates are the second-largest animal group on Earth and includes spiders, ticks and mites. One goal of the U.S. Department of Energy-funded research is to find new ways to combat the spider mite and other pests. The estimated cost of chemical pest control of spider mites is more than $500 million worldwide.

"Spider mites are a huge problem for agriculture because they are very difficult to get rid of," said Pires da Silva. "They're very small, they reproduce in huge numbers and they become very easily resistant to chemicals used to try to control them."

The information from the genome-sequencing project has provided insight into how the spider mite evolves and interacts with the plants it is attacking, researchers said.

"We have discovered this creature's gene set, and more importantly, we believe we have found its Achilles heel so that we can begin development of non-pesticide, alternative pest control measures," says Grbić, a biology professor in Western's Faculty of Science.

Spider mite reproduction is similar to bees. Eggs that are fertilized become females and those that are unfertilized develop into males. Pires da Spider mite (Image from www.insectimages.org) Silva's role in the sequencing project was to look at the newly revealed genome and try to discern how this gender determination process developed. After comparing the spider mite to known genomes, such as fruit fly, bee and mouse, he found that genes involved in gender determination in the spider mite are likely very different.

"With this project, we now know that genes involved in sex determination in other animals are not involved in sex determination for the spider mite," Pires da Silva said. "The genome sequence gave us that first step. If we can figure out which genes do play a role in sex determination, we may be able to manipulate those functions to control the spider mite population."

Pires da Silva's laboratory at UT Arlington also has been exploring sex determination in the Rhabditis, a nematode worm about 1 mm long that produces both males, females and hermaphrodites. He believes methods developed in that research could be useful in further study of the spider mite.

"Dr. Pires da Silva is on the cutting-edge of explorations that will allow scientists to address a serious agricultural concern while learning more about evolutionary biology," said Pamela Jansma, dean of the UT Arlington College of Science. "Revealing the structure of the spider mite's genome has opened up a world of possibilities for researchers. We are proud he is a part of this effort."