Physiology and genetics of nitrogen uptake in the tree/mycorrhizal holobiont

植物面临着扎根的独特挑战。 它们必须在整个生命周期中从一个地方获取营养，就树木而言，需要几个世纪。 北方森林树木面临着额外的挑战，因为土壤通常是寒冷的，酸性的和低的可用养分，特别是氮（N）。了解树木对氮限制土壤的适应性，以及这些适应性如何塑造树木对气候变化的反应是一个重要的实践和科学目标。 * 在自然系统中，树根与真菌伙伴，真菌，这是至关重要的营养矿化，吸收和转移的过程。有些人甚至认为，这棵树不是一个独立的实体，而是一个全生生物，依赖于它的微生物群。菌根类型和物种在分解有机质和吸收营养物质的能力上有所不同，但我们对菌根之间的变化或温度或CO2对共生关系的影响知之甚少。 该提案描述了一个程序的相互作用的树木根系与外生和丛枝菌根真菌，和N的吸收和N-形式的喜好的菌根对比温度，N的可用性和CO2的条件下的研究。我们将探索宿主植物和微生物伴侣的基因型之间的相互作用，重点关注宿主植物的生长和营养。我过去的工作集中在针叶树和外生菌根真菌之间的伙伴关系。我们已经表明，真菌物种之间的N相关的功能性状的差异是适应不同的N形式的可用性，真菌的合作伙伴在控制N的吸收发挥了关键作用。该研究的目的是评估树木和菌根物种和基因型之间的相互作用，以及环境因素的N形式的有效性，温度和CO2。随着全球气温上升和土壤变暖，这些相互作用将对氮的吸收产生重大影响，从而影响森林的生长和群落结构。 我将研究在细胞和全根水平上的氮吸收速率和形式，氮吸收基因的表达，以及CO2浓度如何影响树木和真菌之间的氮碳平衡。这项工作将加深我们对菌根共生体功能多样性的理解。 它将揭示森林对全球变化的反应的潜在复杂性以及改善森林增长的手段。 该研究旨在培训UVic森林生物学中心的四名研究生和十名本科生。

Plants face the unique challenge of being rooted in place. They must acquire nutrients from one location over an entire lifetime in the case of trees, over centuries. Northern forest trees face an additional challenge because soils are typically cold, acidic and low in available nutrients, particularly nitrogen (N). Understanding the adaptations of trees to N-limited soils, and how these adaptations may shape tree response to changing climates is an important practical and scientific goal. ******In natural systems, tree roots associate with fungal partners, mycorrhizae, that are vital to the processes of nutrient mineralization, uptake and transfer. Some go so far as to suggest that the tree is not a standalone entity but a holobiont, dependent on its microbiota. Mycorrhizal types and species differ in their ability to break down organic matter and take up nutrients, but we know little about variation among mycorrhizae or about temperature or CO2 effects on the symbiosis. This proposal describes a program of research on the interaction of tree roots with ecto- and arbuscular mycorrhizal fungi, and the N uptake and N-form preferences of the mycorrhizae under conditions of contrasting temperature, N availability and CO2. We will explore the interaction of genotypes of host plant and microbial partner, with a focus on the growth and nutrition of the host plant.******My past work has focused on the partnership between conifers and ectomycorrhizal fungi. We have shown that differences in N-related functional traits among fungal species are adaptations to varying N form availability, and that the fungal partners play a key role in controlling N uptake. The objective of the proposed research is to evaluate the interactions among tree and mycorrhizal species and genotypes, and the environmental factors of N form availability, temperature and CO2. As global temperatures rise and soils warm, these interactions will have significant implications for N uptake, and thus forest growth and community structure. I will investigate the rate and form of N uptake at the cellular and whole-root level, the expression of genes integral to N uptake, and how CO2 concentration affects the N-carbon balance between the tree and fungus.******This work will deepen our understanding of the functional diversity in mycorrhizal symbioses. It will reveal potential complexities in forest response to global change and means to improve forest growth. The research is designed for the training of four graduate students and ten undergraduates in the UVic Centre for Forest Biology.*****