Ecophysiology of ectomycorrhizal symbioses

外生菌根共生的生态生理学

• 批准号: RGPIN-2018-03927
• 负责人: Jones, Melanie
• 金额: $ 6.85万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=761653
• 关键词: Ecophysiology; ectomycorrhizal; symbioses

Ectomycorrhizae are ancient symbiotic relationships between fungi and plant roots. Many members of the pine, birch, willow and beech families depend heavily on these fungal partners for adequate uptake of mineral nutrients. In my lab, we look at the dual function of ectomycorrhizal fungi (EMF): as symbionts that can translocate nitrogen (N), phosphorus (P) and other mineral nutrients to their plant partners, and as soil fungi that, by excreting degradative enzymes, contribute to the breakdown of soil organic matter and the cycling of carbon (C), N, P and sulphur (S). Because EMF play a major role in plant nutrient uptake, they will be important in the migration or adaptation of trees in response to environmental change. We plan to investigate whether different EMF communities use different strategies for acquiring P depending on the types of P (organic vs inorganic) that dominant the soils in which they are found. If EMF communities are locally adapted, forest managers will need to manage both the trees and EMF if replanting programs are changed as a result of climate change. One of my students recently observed a major loss of N from pine seedlings when their EMF were supplied with nutrients after a period of starvation. This suggests that N moved from seedling to fungus, which is counter to conventional understanding of the symbiosis. We will test this hypothesis by labelling foliage, as well as hyphae, with 15N and quantify translocation of N in both directions using both mass spectrometry and sophisticated microscopic approaches. If movement of N from plant to EMF is confirmed, we will collaborate with an international expert to study behavior of N transporters at the root-fungal interface in mycorrhizal roots. We will also follow the germination and colonization of pine seedlings in the field and greenhouse to see if we can detect any short-term shift in the direction of N transport after a sudden change in soil nutrient status. This research will challenge the conventional view of N transport in ectomycorrhizal plants especially during seedling establishment, and increase understanding of N transport at the mycorrhizal interface. While it is accepted that EMF break down soil organic matter to access N, P and S, there is much debate about whether EMF meet any of their C needs from soil C, given that they have direct access to recently fixed C in roots of their plant hosts. We will test for saprotrophic behavior of EMF in the lab by growing ectomycorrhizal pine with 13C-labelled soil C. We will quantify the proportion of C acquired from soil vs roots by analyzing C isotope signatures in the phospholipids of the EMF. Through this research, and with the involvement of international collaborators, four honours, three MSc, and two PhD students will be trained in the use of sophisticated microscopic, isotopic and molecular techniques to study how EMF affect seedling establishment and nutrient cycling in Canadian forests.

外生菌根是古老的真菌和植物根之间的共生关系。松树、桦树、柳树和山毛榉家族的许多成员严重依赖这些真菌伙伴来充分吸收矿物质营养。在我的实验室里，我们研究了外生菌根真菌的双重功能：作为共生体，可以将氮(N)、磷(P)和其他矿物质养分转移到它们的植物伙伴；作为土壤真菌，通过排泄降解酶，有助于土壤有机质的分解和碳(C)、氮、磷和硫的循环(S)。由于电动势在植物养分吸收中起着重要作用，因此它们在树木适应环境变化的迁移或适应过程中将发挥重要作用。我们计划调查不同的EMF群落是否使用不同的策略来获取P，这取决于P(有机和无机)的类型，这些类型主导着发现它们的土壤。如果EMF社区是当地适应的，如果重新种植计划因气候变化而改变，森林管理者将需要同时管理树木和EMF。我的一个学生最近观察到，在一段时间的饥饿后，当松树幼苗的电动势得到营养供应时，他们的氮素大量损失。这表明N从幼苗转移到真菌，这与传统的共生认识背道而驰。我们将通过用15N标记树叶和菌丝来检验这一假说，并使用质谱学和复杂的显微方法来量化N在两个方向上的转移。如果证实了N从植物到EMF的移动，我们将与一位国际专家合作，研究N转运蛋白在菌根-真菌界面的行为。我们还将跟踪松树幼苗在田间和温室内的萌发和定植情况，看看在土壤养分状况突然变化后，我们是否能检测到氮素运输方向的任何短期变化。这项研究将挑战外生菌根植物特别是幼苗形成过程中氮素运输的传统观点，并加深对菌根界面氮素运输的理解。虽然人们普遍认为电动势能分解土壤有机质以获取N、P和S，但由于电动势能直接获取植物根部新近固定的碳，因此对于电动势是否能满足土壤C的需求还存在很大争议。我们将在实验室通过用13C标记的土壤C种植外生菌根松来测试EMF的腐生营养行为。我们将通过分析EMF磷脂中的碳同位素特征来量化从土壤中获得的C与从根中获得的C的比例。通过这项研究，在国际合作者的参与下，四名荣誉学生、三名硕士和两名博士生将接受使用复杂的显微、同位素和分子技术的培训，以研究电动势如何影响加拿大森林的苗木建立和养分循环。