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之间的互惠共生关系。外生菌根(ECM)在许多重要的经济林木上形成，包括松科植物，而环状菌根(ERM)则存在于杜鹃花科植物(如越橘)上。菌根网络(MN)是指两种或两种以上植物的根与同一真菌菌丝体相结合而形成的。连接到MN可以提高新建立的苗木的存活率和生产力，从而增加森林的弹性。大多数菌根网络的研究都集中在ECM或丛枝菌根网络上，而对ERM网络知之甚少。我的计划的短期目标是确定：1)两个形成网络的ECM真菌物种形成的基因的平均寿命；2)ERM是否形成广泛的和潜在的功能网络；3)ERM真菌在不同环境条件下分解土壤有机碳和循环养分的能力。对于目标1，我的团队将在三年内从第一年抽样的几米内采集的样本中确定基因类型。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类型和5-12年前收集的基因类型。如果网络持续多年，这表明网络的好处可能会一年比一年多。对于目标2，我的团队将收集与轶事观察有关的数据，即越桔树种在靠近大针叶树的地方生长得更大。此外，我们将检验两个菌根寄主(云杉和哈克莓)彼此形成MNS的假设。我们将绘制和量化越橘/云杉的分布图，鉴定云杉和越橘根部共同存在的真菌，并在实验室中三方共生种植它们。这些信息将对两个易受拟人化干扰的地区的恢复很有价值：亚高山森林和北部针叶林。对于目标3，为了研究ERM真菌的腐生营养能力，我们将选择编码碳水化合物和植物细胞壁降解酶的基因。我们将使用最近生成的3个抄本中的信息来完成这项工作。我们将量化这些基因的表达，并在真菌自由生活和共生时、在不同的底物复杂性之间以及在植物共生体向真菌提供不同水平的碳之间进行比较。这些信息将为气候变化模型估计二氧化碳排放到大气中提供有价值的信息。该项目总共将培养14名HQP(2名硕士、3名博士和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).