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

随着全球贸易和气候变化的增加，加拿大森林的生态和经济可持续性越来越受到本地和外来入侵昆虫的威胁，这些昆虫携带真菌病原体到商业和观赏树木。目前在加拿大西部发生的山松甲虫（MPB）流行病说明了这种流行病的破坏性即时和长期影响的规模，它涉及宿主、媒介和病原体之间的特定相互作用。MPB的传播是通过甲虫群大规模攻击黑松，克服树的防御，然后在树皮下的通道中繁殖。以mpb为载体的真菌是该流行病的关键共生成分，因为它们为甲虫克服树木防御提供了必要的帮助，随后成为甲虫后代的营养来源。当带菌真菌绕过树木的物理和化学防御时，它们迅速在树木的韧皮部和边材上定居，并通过阻止水分输送到树冠而杀死树木。此外，真菌还会污染树木的边材，降低木材和木材纤维的工业价值。病媒真菌是树型病原体；在没有甲虫的情况下，它们可以杀死树木。我们的主要目标将是蓝染真菌锁形蛇瘤，这是加拿大西部流行病中最具致病性的真菌MPB关联。我们的长期目标是阐明真菌致病性的机制。具体来说，我们将识别天然存在的油树脂和酚类杀菌剂，它们是黑松防御系统的主要组成部分，并将描述它们如何干扰O. clavigerum的萌发和生长。我们将使用生化和分子方法，利用我们之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.