Ecology and chemistry of plant-microbiome interactions in iron-deficient soil

2021 Fiscal Year Annual Research Report

• Project/Area Number: 20F20084
• Research Institution: Kyoto University
• Principal Investigator: 東樹 宏和 京都大学, 生態学研究センター, 准教授 (60585024)
• Co-Investigator(Kenkyū-buntansha): CANARINI ALBERTO 京都大学, 生態学研究センター, 外国人特別研究員
• Project Period (FY): 2020-09-25 – 2023-03-31
• Keywords: 共生 / 土壌 / 植物

Outline of Annual Research Achievements

We aimed at achieving several goals with the overall intent to deepen the scientific understanding of plant microbiome research. We planned experiments investigating competition/cooperation dynamics between arbuscular mycorrhizae fungi (AMF) and other root endophytic fungi. Our early achievements (until now) can be summarized in the following points: 1)Outline of a specific experimental approach and set up of a research network for the theoretical and technical support for different aspects of the research plan (including multiple partners within and outside Japan) and purchase of all the necessary items. 2)Set up of a methodology to allow concomitant extraction/measurement of fatty acid biomarkers and ergosterol. We developed this technique in our laboratories which will allow us to trace 13C labelled carbon into different fungal groups. 3)Set up and test of visualization techniques suitable for the staining of both AMF and other endophytic fungi growing in plant roots. 4)Optimization of growing substrate to allow AMF and endophytic fungi colonization of plant roots in nitrogen rich and limited conditions. 5)Optimization of a in vitro set up for the quantification of carbon to nitrogen exchange in an anexic plant-endophytic fungi system.
We are currently running a test for developing a split root system for the dual colonization of growing plant by AMF and endophytic fungi. We are also screening the effects of several endophytic fungal strains on two model plants: Lotus japonicus and Solanum lycopersicum cv. Micro-Tom.

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

We successfully set up experimental systems for observing the interface of below-ground plant-fungus interactions. In particular, we optimized the system for tracking the exchange of carbon and nitrogen between plants and endophytic/mycorrhizal fungi based on a series of chemical analyses such as PLFA/NLFA analyses and stable isotope analyses. The systems are broadly applicable to studies experimentally evaluating the effects of symbionts or hosts on the performance of respective organisms. The chemical-ecology-based analyses will be extended to multidisciplinary analyses utilizing gene expression (transcriptomic) analyses with RNA-seq.

Strategy for Future Research Activity

To summarize the Research Plan for the fiscal year 2022, we listed a series of objectives (and the rationale) that we aim to achieve:
1)Finalise tests to on effects of endophytes on model plant species: this will allow to select specific species of interest for further experiments.
2)Finalise tests to calibrate the necessary condition to successfully achieve stable isotope tracing techniques: these tests will allow us to characterize the necessary conditions to achieve measurable amounts of stable isotope tracer incorporated in different biomarkers for fungi and in plant biomass.
3)Carry an in vitro experiment to test competition dynamics between different root endophytic fungi and arbuscular mycorrhizae during nitrogen and carbon exchange with a model plant: this experiment will allow us to understand how endophytic fungi that carry similar function to AMF can modify the trading feature of carbon and nitrogen exchange in the AMF-plant symbiosis.
4)Carry a pot experiment to validate the in vitro results: this experiment will allow us to generalize the findings obtained in in vitro conditions to soil-grown plants.