Structure and function of mycorrhizal networks in North American forests

我的团队研究计划的总体目标是探索北美森林中菌根网络的结构和功能。菌根是真菌和植物根系之间的互惠共生关系。外生菌根（ECM）形成于许多经济上重要的林木上，包括松树科的成员，而杜鹃花科菌根（ERM）发现于植物科杜鹃花科的成员上（例如，huckleberry）。当两种或两种以上植物的根与同一真菌菌丝体结合时，就会形成菌根网络。与MN的联系可以提高新建立的幼苗的存活率和生产力，从而增加森林的复原力。大多数菌根网络的研究都集中在ECM或丛枝菌根网络，而很少有人知道ERM网络。我的计划的短期目标是确定：1）由两个网络形成ECM真菌物种形成的基因型的平均寿命; 2）ERM是否形成广泛的和潜在的功能网络;和3）ERM真菌在不同环境条件下分解土壤有机碳和再循环养分的能力。对于目标1，我的团队将在三年的时间内从第一年采样的样本中确定基因型。为了获得长期营业额的概念，我们将比较前三年确定的基因型与5-12年前收集的基因型。如果网络持续多年，这表明网络的好处可以从一年到下一年复合。对于目标2，我的团队将收集与轶事观察有关的数据，即当靠近大型针叶树时，越桔物种会变大。此外，我们将测试的假设，两个菌根主机（云杉和越橘）形成MN与对方。我们将绘制和量化越橘/云杉分布，确定云杉和越橘根共同的真菌，并在实验室中将它们培养在三方共生体中。这一信息对于恢复两个易受拟人干扰的地区-亚高山森林和北方森林-将是宝贵的。对于目标3，为了研究ERM真菌的腐殖能力，我们将选择编码碳水化合物和植物细胞壁降解酶的基因。我们将使用来自3个最近生成的转录组的信息来做到这一点。我们将量化这些基因的表达，并比较它们时，真菌是自由生活与共生，在不同的基板复杂性，并在不同水平的碳供应的真菌从植物共生体。这些信息将为气候变化模型提供有价值的信息，以估计二氧化碳向大气中的释放。总的来说，该计划将培养14名HQP（2个硕士，3个博士学位，9名本科生）。

The overall objective of my team’s research program is to explore the structure and function of mycorrhizal networks in North American forests. A mycorrhiza is a mutualistic symbiotic association between fungi and plant roots. Ectomycorrhizas (ECM) are formed on many economically important forest trees including members of the pine family, whereas ericoid mycorrhizas (ERM) are found on members of the plant family Ericaceae (eg., huckleberry). A mycorrhizal network (MN) occurs when roots of two or more plants associate with the same fungal mycelium. Linkage into an MN can improve the survival and productivity of newly established seedlings, which adds to the resilience of forests. Most mycorrhizal network studies have focussed on ECM or arbuscular mycorrhizal networks, whereas little is known about ERM networks. The short-term objectives of my program are to determine: 1) the average life-span of genotypes formed by two network-forming ECM fungal species; 2) whether ERM form extensive and potentially functional networks; and 3) the ability of ERM fungi to break down soil organic carbon and recycle nutrients under varying environmental conditions. For Objective 1, my team will identify genotypes over a three-year period from samples taken within metres of those sampled in the first year. To obtain an idea of longer-term turnover, we will compare genotypes identified in the first three years with those collected 5-12 years ago. If networks last for multiple years, this suggests that benefits of the network could compound from one year to the next. For Objective 2, my team will collect data relating to anecdotal observations that Vaccinium species grow larger when located close to large conifer trees. In addition, we will test the hypothesis that two mycorrhizal hosts (spruce and huckleberry) form MNs with each other. We will map and quantify huckleberry/spruce distributions, identify the fungi that are common to both spruce and huckleberry roots, and grow them in tripartite symbioses in the lab. This information will be valuable for the rehabilitation of two areas that are vulnerable to anthropomorphic disturbances: the subalpine and boreal forests. For Objective 3, to investigate saprotrophic abilities of an ERM fungus we will select genes coding for carbohydrate and plant cell wall-degrading enzymes. We will use information from 3 recently generated transcriptomes to do this. We will quantify the expression of these genes and compare them when the fungi are free living vs. in symbiosis, among varying substrate complexities, and among varying levels of carbon supply to the fungus from the plant symbiont. This information will provide valuable information to climate change models estimating carbon dioxide release into the atmosphere. In total, this program will train 14 HQP (2 MSc., 3 Ph.D., and 9 undergraduate students).