In their natural environment, plants are constantly exposed to a wide variety of microbes. These include plant pathogens, which can infect the plant tissue to gain access to energy: soil-borne pathogens enter into root, but also can migrate to xylem or phloem. Air-borne pathogens infect aerial parts such as leaves, stems, or fruits.

We aim at understanding various aspects of the infection process in two different fungal systems:

• Ustilago maydis / Zea mays
• Thecaphora thlaspeos / Arabis spps

A Spotlight of our work within CEPLAS has just been released!

In the past years, we have established the Brassicaceae smut fungus T. thlaspeos as a smut infection system in the model plant A. thaliana, described its lifecycle (Frantzeskakis 2017 https://doi.org/10.1094/MPMI-08-16-0164-R), and established a transformation protocol (Plücker 2021 https://doi.org/10.3390/jof7010038). This pipeline now serves as a blueprint for the investigation of fungi from the Thecaphora clade such as T. frezii, which is a major problem for peanut production in Argentina.

T. thlaspeos has several distinctive features when compared to the grass smut fungi:

1. Teliospores germinate only in the presence of a plant signal.
2. Germination gives rise to haploid filaments, not yeast-like cells as in U. maydis.
3. The fungus colonizes both shoots and roots.
4. It undergoes a life-long interaction with its perennial host plant.

Nevertheless, the genome and infection transcriptome resembles the grass smuts fungi to a great extent (Courville 2019 https://doi.org/10.1111/nph.15692) including the mating genes and a subset of the core effector proteins.

We now are interested in uncovering the common principles and distinctive molecular mechanisms that determine the infection process and host colonization in a comparative approach.

In the recent years it became evident that pathogens can use various RNA species as a tool  to infect/to support infection of their host plant. In this project associated to the research unit exRNA, we focus on RNA-based communication during the infection. First, small RNAs are used in cross-kingdom RNAi. In this project, we aim at uncovering T. thlaspeos sRNAs that target host plant genes to understand their contribution to fungal virulence. The reverse pathway of plant RNAs counter-acting fungal biology is highly relevant in developing novel plant protection strategies, e.g. spray-induced gene silencing (SIGS). Second, since U. maydis also delivers specific mRNAs into the host plant (Kwon 2021 https://doi.org/10.3390/jof7070562), in a comparative approach the extracellular vesicles of T. thlaspeos are characterized with regard to their cargo, and the function of cargo molecules at the target site. In the long term, we aim at elucidating the molecular mechanisms of RNA-transport in extracellular vesicles, their biogenesis and the targeting mechanisms to the host cell.

N. Heucken, K. Tang, L. Huesemann, N. Heßler, K. Müntjes, M. Feldbrügge, V. Göhre, M. D. Zurbriggen (2023) Engineering and implementation of synthetic molecular tools in the basidiomycete fungus Ustilago maydis. J. Fungi

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H. J. Courville, L. Frantzeskakis, S. Gul, N. Haeger, R. Kellner, N. Heßler, B. Day, B. Usadel, Y. K. Gupta, H. P. van Esse, A. Brachmann, E. Kemen, M. Feldbrügge and V. Göhre (2019) Smut infection of perennial hosts: the genome and the transcriptome of the Brassicaceae smut fungus Thecaphora thlaspeos reveal functionally conserved and novel effectors. New Phytol. 222: 1474–1492
doi      PubMed

L. Frantzeskakis, K.J. Courville, L. Plücker, R. Kellner, J. Kruse, A. Brachmann, M. Feldbrügge and V. Göhre (2017) The plant-dependent life cycle of Thecaphora thlaspeos: a smut fungus adapted to Brassicaceae. Mol. Plant-Microb. Interact. 30: 271-282
doi      PubMed