Exploring how the mountain pine beetle fungal associate ophiostoma clavigerum overcomes lodgepole pine defenses

鉴于全球贸易和气候变化的不断增加，加拿大森林的生态和经济可持续性日益受到本土和外来入侵昆虫的威胁，这些昆虫将真菌病原体带到商业和观赏树木上。目前加拿大西部的山松甲虫(MPB)疫情说明了这种流行病的破坏性即时和长期影响的规模，其中涉及宿主、病媒和病原体之间的特定相互作用。MPB疫情通过甲虫种群传播--大规模攻击松树并克服树木防御，然后在树皮下的走廊中繁殖。MPB载体真菌是甲虫疫情中的关键共生成分，因为它们为甲虫克服树木防御提供了必要的帮助，并随后成为甲虫后代的营养来源。当载体真菌绕过树木的物理和化学防御时，它们会迅速侵占树木的韧皮部和边材，并通过阻止水分运输到树冠而杀死树木。此外，真菌还会污染树木边材，降低木材和木材纤维的工业价值。媒介真菌是树木的病原体；在没有甲虫的情况下接种后，它们可以杀死树木。我们的主要目标将是蓝斑真菌Ophiostoma clavigerum，它是加拿大西部疫情中最具致病性的真菌MPB。我们的长期目标是阐明真菌致病的机制。具体地说，我们将确定天然存在的松脂和酚类杀菌剂，这些杀菌剂是樟子松防御系统的主要成分，并将表征它们如何干扰棒状根霉菌的萌发和生长。我们将使用生化和分子方法，利用我们以前工作中产生的分子试剂。

Given increasing global trade and climate change, the ecological and economical sustainability of Canada's forests are increasingly threatened by native and alien invasive insects that carry fungal pathogens to commercial and ornamental trees. The current mountain pine beetle (MPB) epidemic in western Canada illustrates the scale of the devastating immediate and long-term effects of such epidemics, which involve specific interactions between a host, vector and pathogen. The MPB epidemic spreads by a beetle population mass-attacking lodgepole pine trees and overcoming tree defences, then reproducing in galleries under the bark. The MPB-vectored fungi are a key symbiotic component in the epidemic, because they provide essential help to the beetles in overcoming tree defences and subsequently serve as a nutrient source for the beetle progeny. When the vectored fungi have bypassed a tree's physical and chemical defenses, they rapidly colonize the tree phloem and sapwood, and kill the tree by blocking water transport to the crown. As well, the fungi stain the tree sapwood, reducing the industrial value of the wood and wood fibres. The vectored fungi are tree pathogens; they can kill trees when inoculated without the beetles. Our primary target will be the blue-stain fungus Ophiostoma clavigerum, the most pathogenic fungal MPB associate in the western Canada epidemic. Our long-term objective is to clarify the mechanisms of fungal pathogenicity. Specifically, we will identify naturally occurring oleoresin and phenolic fungicides that are the major components of lodgepole pine defence systems, and will characterize how they interfere with germination and growth of O. clavigerum. We will use biochemical and molecular approaches, taking advantage of molecular reagents generated in our previous work.