Invited Speaker Australian Society for Microbiology Annual Scientific Meeting 2021

The dynamic mycorrhizal fungi-trees-soil interaction and how this determines the plant health and soil nutrients in changing climate (#126)

Johanna Wong-Bajracharya 1 2 , Laura Castañeda-Gómez 1 3 , Emiko K Stuart 1 , Krista L Plett 1 2 , Catriona A Macdonald 1 , Ian C Anderson 1 , Yolima Carrillo 1 , Jonathan M Plett 1
  1. Hawkesbury Institute for the Environment, , Western Sydney University, Richmond, New South Wales, Australia
  2. Elizabeth Macarthur Agricultural Institute, Department of Primary Industries NSW, Menangle, New South Wales, Australia
  3. Department of Physical and Environmental Sciences at Scarborough, University of Toronto, Toronto, Canada

Ectomycorrhizal (ECM) fungi form mutualistic interaction with eucalypt trees and this interaction is an important linkage between plant health and soil health. ECM fungal mycelium forms a network of conduit that facilitate trees’ nutrient transfer from soil. On the other hand, ECM fungi also play role in soil organic matter deposition, and priming or competing with other soil microbes. In the future, elevated CO2 conditions (eCO2) is projected to increase plant productivity and nutrient demands, and subsequently alter the dynamic of this tripartite interaction between trees, ECM fungi and soil microbes.

In our previous studies, we have taken a microscopic view on the molecular interaction between the host trees and ECM fungi on a sterile system. We studied the chemical signalling between ECM fungi and eucalypts [1]. We also observed the effect of eCO2 on the nutrient uptake mechanism at a molecular level [2]. In this present study, we added the soil microbes into our equation. Using soil from a native eucalypt forest, we aimed to understand the impact of this tree-ECM fungi-soil microbial interaction under eCO2 and nitrogen limitation in a relatively natural setting.

Using a whole plant-soil system, we have closely examined the impact of CO2 and ECM fungi on the eucalypt root exudation composition using metabolomic approach [3]. In addition, we evaluated the effects of variable CO2, ECM fungi and nitrogen treatments on the root colonization, plant growth, soil nutrient contents and soil microbial activities. Surprisingly, we found that root exudation composition is largely influenced by ECM fungi-tree interaction but not by eCO2 condition. Our results also indicate the impact of ECM fungi on phosphorus and carbon cycling under eCO2 is dependent of the soil nitrogen availability. More findings and insights from this collaborative study between soil science, microbiology and molecular biology would be discussed in my presentation.

  1. Wong, Johanna WH, et al. "The influence of contrasting microbial lifestyles on the pre-symbiotic metabolite responses of Eucalyptus grandis roots." Frontiers in Ecology and Evolution 7 (2019): 10.
  2. Plett, Jonathan M., et al. "The effect of elevated carbon dioxide on the interaction between Eucalyptus grandis and diverse isolates of Pisolithus sp. is associated with a complex shift in the root transcriptome." New Phytologist 206.4 (2015): 1423-1436.
  3. Wong-Bajracharya, Johanna, et al. "Untangling the effect of roots and mutualistic ectomycorrhizal fungi on soil metabolite profiles under ambient and elevated carbon dioxide." Soil Biology and Biochemistry 151 (2020): 108021.