If you had told me a year ago that I would be involved with a group that would decode the spider mite genome, I would have asked “What’s a spider mite?” Since then, I have joined an international consortium as Project Manager and our team just published the sequenced spider mite genome in the prestigious scientific journal, Nature.
First things first, what are spider mites? They are major agricultural pests that feed on more than 1000 different plant species. They are less than 1millimetre long and they destroy many crops such as corn, cucumbers, peppers, tomatoes, apples, pears, and strawberries to name a few. If you have a garden or plants in your home, you may even have spider mites. Have any of your plants turned yellow? Are the leaves brittle and covered in webbing?
One of the reasons spider mites are so destructive is their unique ability to feed on such a variety of plants. They have also developed resistance to pesticides and with only seven days from egg to adult, these pests are the source of many headaches for farmers. Since Ontario is known for growing a large number of greenhouse vegetables (tomatoes, cucumbers, peppers, etc.), this pest is particularly important here at home. With global warming and the ability of mites to multiply even faster in high temperatures, the damage spider mites cause to our field crops is likely to increase.
Miodrag Grbić of the University of Western Ontario has put together an international consortium to study spider mites and the effect they have on agriculture in order to develop strategies to reduce spider mite damage and increase crop yield in the future. The consortium of over 50 researchers from nine different countries has now unveiled the whole genome of this species, which represents the first sequenced genome for the animal group called chelicerates. This is the world’s second largest group of animals (behind insects) and includes ticks, spiders, horseshoe crabs, scorpions and mites. What did the team learn from the genome sequencing? The very small spider mite genome, which is about 30 times smaller than the human genome, contains 18 414 genes. Many of these genes are involved in breaking down toxic compounds in plants, which allows the spider mite to feed on numerous plants and crops. The spider mite will express (or “activate”) different genes and make different detoxification compounds depending on which plant it wants to eat. One very interesting finding is that spider mites acquired genes from bacteria and fungi. They used these ‘borrowed genes’ to modify toxic compounds in plants, leaving the plants defenseless against the mites. The researchers hypothesize that spider mites resist pesticides in a similar way.
Our team looks at both sides of the equation: what happens to the plant as well as what happens to the spider mite during feeding. The idea is to determine the plant defense molecules that are successful at resisting spider mite damage and use this information to develop non-pesticide strategies for pest control. Now that the genome is available, there are 18, 414 targets to study in order to develop new, environmentally-friendly strategies to prevent spider mite damage in agriculture.
Even with all the damage spider mites cause, the research team also discovered something positive. The silk that spider mites produce is very strong and very thin. This means that this light-weight ‘nanomaterial’ has potential uses in the aerospace, automotive and medical industries - for example as a reinforcement in composite materials, matrix for tissue engineering and drug delivery, or biofilms for wound dressing. Research into the properties and potential uses for spider mite silk continues.