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Scientists use genomic research to tackle mountain pine beetle
A new research project probing the genetic blueprint in the war between the mountain pine beetle and the lodgepole pine trees it attacks is expected to yield key information on how molecular-level triggers in a tiny pest can destroy a landscape as vast as Canada’s northern pine forests.
Using $7.8 million in new reseach funding, scientists intend to look at the outbreak as a disease that’s infecting an organism. In this case the organism is the endless pine forest that sweeps across Canada from the British Columbia Interior to Newfoundland.
They want to discover the molecular interactions between the players in what has to be one of nature’s most dramatic battles: a war with the potential to kill a continent-wide eco-system.
And then they intend to overlay their findings on geographic and economic data to aid in forecasting and controlling future outbreaks. That could contribute to forest economics by showing regions where timber supplies are threatened or even where future bioenergy plants could be built using beetle-killed timber for fuel.
The players that scientists want to probe, project co-leader Joerg Bohlmann, said in an interview Monday, are the pine beetle, a bark beetle no larger than a grain of rice, an even tinier fungus carried by the beetle that stains the wood it infects blue, and the host lodgepole pine trees.
All three interact in fascinating and complex ways at the genetic level that are not understood, said Bohlmann who heads a research program on chemical defences of trees at the University of B.C. The beetle and fungus are spreading east from British Columbia and have begun attacking jack pine trees in the boreal forest, initiating a new and posibly different cycle of attack and defence.
“There is a disease-causing biological agent going through the landscape and we do not understand how it really functions,” Bohlmann said. “The bark beetle alone, would not be able to kill the tree.”
The $7.8 million project, conducted in universities and institutions in Alberta and British Columbia, is largely funded by Genome Canada, Genome B.C., and Genome Alberta. It is aimed at cracking the mystery.
Science has already researched the ecology of the beetle, Bohlmann said. It has a symbiotic relationship with the fungus. The beetle burrows into a tree, carrying the blue-staining fungus with it. When the tree reacts by producing toxic pitch, the beetle releases pheromones produced from the tree’s own pitch, completing the symbiotic cycle. That draws other beetles to the new host tree, escalating the stress on the tree and its ability to produce toxic sap. The tree’s defences are overwhelmed.
Once safely inside, the beetle lays its eggs. The larvae produce an anti-freeze that enable them to withstand -40 degree winter temperatures, and the fungus weakens the layer underneath the bark, enabling the larvae to better chew their way through it, killing the tree.
But underlying the landscape-shaping epidemic are molecular-level triggers in genes within all three players that science has yet to crack.
Discovering the genomic triggers that produce anti-freeze in beetles would be a huge discovering it itself.
Researchers hope that, just as diseases in the human body can be defeated by using pharmaceuticals that trigger or block gene receptors, environmentally-safe pesticides could be developed that affect receptors in the beetle, the fungus or the trees to interrupt the disease process.
“We know a fair amount, about infectious diseases in people, like salmonella and how genetic make-up contributes to pathogenicity and how host immune responses can over come it,” Bohlmann said. “But when you take these questions into a forest health scenario, we are shocked at how little we actually know.
“I think the reason for this is that for the longest time we have been looking at forest pest outbreaks almost like a non-biological process, almost as if it were a wind storm, coming through the landscape and laying all the trees flat.”
The project will start with existing scientific understanding and take it to a new level using genomic sequencing.
“The difference that makes this now possible is because we can sequence the genomes of the bark beetle, the bark-beetle-associated tree-killing fungi and possibly even the tree,” he said.
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