Doctor Johanna Wong


Graduate PhD 2020

Thesis title

An exploration of the molecular signals and their effects on the belowground interaction between Eucalyptus grandis and soil fungi of different lifestyles

Research Project

Eucalypts are dominant trees in natural and managed Australian landscapes. As such, they have significant ecological and economic value. Affecting the productivity and sustainability of these trees are the fungi that associate with their root systems. While some fungal species are pathogenic, ectomycorrhizal fungi (ECM fungi) are mutualistically beneficial for eucalypts. Symbiotic ECM fungal association on eucalypt roots improves nutrient acquisition, enhances pathogen resistance and increases tolerance of eucalypts towards drought and heavy metal. The ability to distinguish the nature of their fungal partner (pathogenic or mutualistic?) and respond correspondingly is crucial for the survival of eucalypts.

To interact with neighbouring soil-borne organisms, plant roots exude a mixture of chemical signals including phytohormones, phytoalexins as well as other metabolites and peptides. Root exudates are known to affect the composition of the fungal community surrounding the root system, however only a few chemical signals have been demonstrated to affect the growth of fungi. Little is known about the specificity and diversity, not to mention the molecular functionality, of these chemical signals used by eucalypts communicating with fungi of different lifestyles.

In this project, I aim to identify and characterise the specific chemical signals used by eucalypts to communicate with symbiotic ECM fungi in comparison with fungi of different trophic lifestyles.
The main questions I aim to answer are:

  1. What are the chemical signals that eucalypt roots secrete to communicate with fungi?
  2. Are there differences in the chemical signals when eucalypt roots are interacting with fungi exhibiting different lifestyles?
  3. How do these chemical signals function in symbiotic ECM fungi:eucalypt interactions?

Molecular experimental techniques, next generation sequencing and advanced chemical analytical techniques will be adopted to identify the chemical signals involved in the fungi:eucalypt interaction. Ultimately, this project will help further understanding of the 'languages' the eucalypt use in communicating with the soil microbial community.


Moffitt MC, Wong‐bajracharya J, Shuey LS, Park RF, Pegg GS, Plett JM, (2022) 'Both Constitutive and Infection‐Responsive Secondary Metabolites Linked to Resistance against Austropuccinia psidii (Myrtle Rust) in Melaleuca quinquenervia', Microorganisms, vol.10, no.2, Article no.383

Stuart EK, Castañeda-Gómez L, Macdonald CA, Wong-Bajracharya J, Anderson IC, Carrillo Y, Plett JM, Plett KL, (2022) 'Species-level identity of Pisolithus influences soil phosphorus availability for host plants and is moderated by nitrogen status, but not CO2', Soil Biology and Biochemistry, vol.165, Article no.108520

Wong-Bajracharya J, Singan VR, Monti R, Plett KL, Ng V, Grigoriev IV, Martin FM, Anderson IC, Plett JM, (2022) 'The ectomycorrhizal fungus Pisolithus microcarpus encodes a microRNA involved in cross-kingdom gene silencing during symbiosis', Proceedings of the National Academy of Sciences of the United States of America, vol.119, no.3, Article no.e2103527119

Plett JM, Plett KL, Wong-Bajracharya J, Pereira MD, Costa MD, Kohler A, Martin F, Anderson IC, (2020) 'Mycorrhizal effector PaMiSSP10b alters polyamine biosynthesis in Eucalyptus root cells and promotes root colonization', New Phytologist, vol.228, no.2, pp 712-727

Wong JW-H, Plett KL, Natera SHA, Roessner U, Anderson IC, Plett JM, (2020) 'Comparative metabolomics implicates threitol as a fungal signal supporting colonization of Armillaria luteobubalina on eucalypt roots', Plant Cell and Environment, vol.43, no.2, pp 374-386

Wong-Bajracharya J, Castañeda-Gómez L, Plett KL, Anderson IC, Carrillo Y, Plett JM, (2020) 'Untangling the effect of roots and mutualistic ectomycorrhizal fungi on soil metabolite profiles under ambient and elevated carbon dioxide', Soil Biology and Biochemistry, vol.151, Article no.108021

Wong JWH, Lutz A, Natera S, Wang M, Ng V, Grigoriev I, Martin F, Roessner U, Anderson IC, Plett JM, (2019) 'The Influence of Contrasting Microbial Lifestyles on the Pre-symbiotic Metabolite Responses of Eucalyptus grandis Roots', Frontiers in Ecology and Evolution, vol.7, Article no.10

Wong JWH, Plett JM, (2019) 'Root renovation: how an improved understanding of basic root biology could inform the development of elite crops that foster sustainable soil health', Functional Plant Biology, vol.46, no.7, pp 597-612

Li MW, Muñoz NB, Wong CF, Wong FL, Wong KS, Wong JWH, Lam HM, (2016) 'QTLs Regulating the Contents of Antioxidants, Phenolics, and Flavonoids in Soybean Seeds Share a Common Genomic Region', Frontiers in Plant Science, vol.7, Article no.854

Ku YS, Wong JWH, Mui Z, Liu X, Hui JHL, Chan TF, Lam HM, (2015) 'Small RNAs in Plant Responses to Abiotic Stresses: Regulatory Roles and Study Methods', International journal of molecular sciences, vol.16, no.10, pp 24532-24554

Yim AKY, Wong JWH, Ku YS, Qin H, Chan TF, Lam HM, (2015) 'Using RNA-Seq Data to Evaluate Reference Genes Suitable for Gene Expression Studies in Soybean', PloS one, vol.10, no.9, e0136343

Research Supervisors

Dr Jonathan Plett, Professor Ian Anderson