Pine terpenoid defences in the mountain pine beetle epidemic and in other conifer pest interactions: specialized enemies are eating holes into a diverse, dynamic and durable defence system
Pine terpenoid defences in the mountain pine beetle epidemic and in other conifer pest interactions: specialized enemies are eating holes into a diverse, dynamic and durable defence system
复制标题
DOI：
10.1093/treephys/tps065
复制
发表时间：
2012-08-01
期刊：
影响因子：
4
通讯作者：
Bohlmann, Joerg
中科院分区：
文献类型：
--
作者：
Bohlmann, Joerg
在过去的15年里，山松甲虫（MPB; Dendroctonus ponderosae Hopkins）及其相关真菌病原体（例如，Grosmannia clavigera Robinson-Jeffrey & RW Davidson）的流行席卷了加拿大西部约1500万公顷的黑松（Pinus contorta Douglas）森林，也侵染了美国西北部大片的松林。MPB和蓝染真菌的共生杀死了松树，留下了枯树景观、经济争夺和腐烂树木大量增加碳排放的可能性（Kurz et al. 2008）。在适宜寄主树木数量过量的推动下，随着气候变暖的影响，MPB/真菌复合体的快速增长的种群继续无视一些关于这种流行病何时何地达到极限的传统预测：我们现在知道MPB流行病已经向北进一步蔓延，并攀升到比预测更高的海拔（Samarasekera, 2012）；它已经从西向东越过了落基山脉的“屏障”；而且，正如最近分子标记所记录的那样（Cullingham et al. 2011）， MPB已经成功地将其东部寄主范围从黑松扩展到杰克松（Pinus banksiana Lamb）。短叶松已成为MPB及其带菌性真菌病原体进入落基山脉东部北方森林广阔景观的前线寄主物种（Safranyik et al. 2010, Cullingham et al. 2011）。与它的兄弟物种，黑松不同，黑松的范围在历史上与MPB及其真菌重叠，杰克松可能没有与MPB/真菌疾病系统共同进化其防御能力，这为该流行病将如何发展提供了新的不确定性。松树对害虫和真菌的主要防御包括特殊的化学物质，如油树脂和酚类化合物的萜类，以及解剖结构，如厚厚的树皮、本构性和创伤性树脂管和特化的韧皮部薄壁细胞（Franceschi et al. 2005）。油树脂具有物理和化学防御系统，主要由单萜烯和二萜树脂酸组成（Trapp和Croteau 2001， Keeling和Bohlmann 2006a， 2006b）。作为复杂化学成分的物理屏障，甲虫攻击时伤口部位的树脂流动、树脂流动的动员和进入树木后朝向树皮甲虫和真菌活动部位的额外树脂形成，以及树脂体积和成分的变化，提供了一组复杂的参数，必须在评估宿主树的防御能力以及这种能力如何受到树木健康的影响时加以考虑。环境与害虫（Raffa et al. 2005, Boone et al. 2011, Ott et al. 2011, Clark et al. 2012, Novick et al. 2012）。萜类防御，包括油树脂的积累和挥发性排放，及其潜在的生化途径在几种针叶树物种中得到了很好的表征（Keeling和Bohlmann 2006a， 2006b）。云杉的种类如挪威云杉（Picea abies Karst.）、白云杉（Picea glauca (Moench) Voss）和锡特卡云杉（Picea sitchensis (Bong.)）)已经建立了一个关于针叶树萜类防御的解剖学、化学、生化、分子和基因组方面信息的参考系统（Zulak和Bohlmann 2010， Hall等人，2011，Hamberger等人，2011，Keeling等人，2011）。一些云杉物种也被描述为萜类化合物在树虫或树真菌相互作用中的作用(例如，Byun-McKay et al. 2006, Zeneli et al. 2006；
During the last 15 years, an epidemic of mountain pine beetle (MPB; Dendroctonus ponderosae Hopkins) and its associated fungal pathogens (eg, Grosmannia clavigera Robinson-Jeffrey & RW Davidson) has swept through~ 15 million hectares of lodgepole pine (Pinus contorta Douglas) forests in western Canada and has also infested large areas of pine forests in the northwestern USA. The pine-killing symbiosis of MPB and bluestaining fungi has left behind landscapes of dead trees, an economic scramble and the potential for massively increased carbon emissions from decaying trees (Kurz et al. 2008). Fuelled by an overabundance of suitable host trees and following the trail blazed by warming climates, rapidly growing populations of the MPB/fungus complex have continued to defy some traditional predictions as to when and where this epidemic would reach its limits: we now know that the MPB epidemic has spread further north and climbed into higher elevations than predicted (Samarasekera, 2012); it has crossed the Rocky Mountain ‘barrier’from west to east; and—as recently documented with molecular markers (Cullingham et al. 2011)—the MPB has successfully expanded its eastern host range from lodgepole pine into Jack pine (Pinus banksiana Lamb.). Jack pine has become a frontline host species through which the MPB and its vectored fungal pathogens have gained entrance into a wide landscape of boreal forest east of the Rocky Mountains (Safranyik et al. 2010, Cullingham et al. 2011). Unlike its sibling species, lodgepole pine, whose range is historically overlapping with that of MPB and its fungi, Jack pine may not have co-evolved its defences with the MPB/fungus disease system, which offers new uncertainties as to how the epidemic will play out. The major defences of pines against insect pests and fungi include specialized chemicals such as terpenoids of oleoresin and phenolics, as well as anatomical structures such as thick bark, constitutive and traumatic resin ducts and specialized phloem parenchyma cells (Franceschi et al. 2005). Oleoresin presents both a physical and chemical defence system against stem-boring insects and is composed mostly of monoterpenes and diterpene resin acids (Trapp and Croteau 2001, Keeling and Bohlmann 2006a, 2006b). As a physical barrier of complex chemical composition, resin flow at wound sites upon beetle attack, mobilization of resin flow and additional formation of resin directed towards the sites of bark beetle and fungal activity after entering the tree, as well as variation of resin volume and composition, present a complex set of parameters that have to be considered in the assessment of host tree defence capacity and how this capacity may be affected by tree health, environment and pests (Raffa et al. 2005, Boone et al. 2011, Ott et al. 2011, Clark et al. 2012, Novick et al. 2012). Terpenoid defences, including accumulation of oleoresin and volatile emissions, and their underlying biochemical pathways are well characterized in several conifer species (Keeling and Bohlmann 2006a, 2006b). Species of spruce such as Norway spruce (Picea abies Karst.), white spruce (Picea glauca (Moench) Voss) and Sitka spruce (Picea sitchensis (Bong.) Carr.) have been established as a reference system for information on anatomical, chemical, biochemical, molecular and genomic aspects of conifer terpenoid defences (Zulak and Bohlmann 2010, Hall et al., 2011, Hamberger et al., 2011, Keeling et al. 2011). Species of spruce have also been characterized for the roles of terpenoids in tree–insect or tree–fungal interactions (eg, Byun-McKay et al. 2006, Zeneli et al. 2006,