Junior group: Algal Symbioses and Interaction Biology
Our junior group investigates how green algae perceive, respond to, and interact with microbial partners. Our work focuses on algal–fungal interactions as tractable systems to uncover the cellular and molecular mechanisms that determine whether microbial encounters become mutualistic, neutral, or parasitic.
Green algae frequently co-occur with fungi in terrestrial and aquatic environments, including soils, biological soil crusts, rock surfaces, plant-associated microbiomes, and lichen-like associations. Despite their ecological importance, the molecular mechanisms underlying algal–fungal interactions remain poorly understood. This is partly because many natural systems are complex, difficult to cultivate, and not easily accessible to genetic manipulation.
Our work uses experimentally tractable algal–fungal systems to bridge this gap. We combine defined co-culture experiments, microscopy, physiological measurements, transcriptomics, and genetics to understand how algae and fungi recognize each other, establish physical and metabolic associations, and respond to environmental stress. A central goal is to uncover the algal mechanisms that determine whether fungal encounters lead to beneficial interactions or detrimental outcomes.
Ongoing projects
Genetic dissection of algal pathways in fungal mutualism
In this project, we investigate the molecular mechanisms underlying the interaction between the model alga Chlamydomonas reinhardtii with the soil-borne fungus Verticillium dahliae. Under defined laboratory conditions, C. reinhardtii and V. dahliae form a contact-associated interaction that promotes both algal and fungal growth and improves algal performance under stress.
Mutualistic interactions between C. reinhardtii and V. dahliae where algal cells attach to fungal hyphae (black arrowheads) and both organisms show increased biomass in co-culture (figure taken from Prockl et al. 2026).
We aim to identify the algal genes and cellular processes required for this mutualistic interaction. To do this, we combine physiological assays, microscopy, transcriptomics, and forward genetics using Chlamydomonas mutant resources. This project asks how algae perceive fungal partners, how they respond at the transcriptional and physiological level, and which algal pathways are required to establish and maintain mutualism.
Algal responses across differential interactions with Verticillium
Algal–fungal interactions are not uniform: closely related algae can respond very differently to the same fungal partner. In this project, we investigate how diverse green algae respond to interaction with Verticillium dahliae, ranging from beneficial to detrimental outcomes.
Algal responses to the presence of V. dahliae vary between species ranging from increased growth and vitality to severe stress.
By comparing algal physiological responses, growth dynamics, stress phenotypes, and transcriptional changes across different algal species, we aim to identify algal traits and response programs associated with compatibility or sensitivity to fungal presence. This comparative approach allows us to ask whether beneficial interactions rely on conserved algal responses or whether different algae use distinct strategies to tolerate, accommodate, or resist fungal partners.
Fungal determinants of algal-fungal interaction outcomes
In collaboration with AG Thomma, we also investigate the fungal side of algal–fungal interactions. This project focuses on fungal gene expression, metabolism, and candidate interaction factors that may contribute to partner compatibility and interaction outcome. By integrating fungal transcriptomics with our algal response analyses, we aim to understand algal–fungal interactions as reciprocal processes shaped by both partners.
V. dahliae transcripts cluster depending on the algal partner (Vd: V. dahliae, Cv: Coccomyxa, Me: Mesotaaenium).
People
Hanna Rövenich (Principal Investigator)
Zoe Prockl (PhD Candidate)
Heidrun Haeweker (Technical Assistant, shared with the Thomma lab)
We are associated with the SFB 1535 MiBiNet.
Relevant literature
Prockl Z, Neubacher U, Rovenich H (2026) The model alga Chlamydomonas reinhardtii forms mutualistic interactions with Verticillium fungi. BioRxiv
Kraege A., Chavarro-Carrero E., Schnell E., Heilmann-Heimbach S., Becker K., Köhrer K., Huettel B., Sargheini N., Schiffer P., Waldvogel A., Thomma B. P. H. J., Rovenich H. (2025). High quality genome assembly and annotation (v1) of the eukaryotic freshwater microalga Coccomyxa elongata SAG 216-3b. G3 15(2):jkae294.
Kraege A, Chavarro-Carrero E, Guiglielmoni N, Schnell E, Kirangwa J, Heilmann-Heimbach S, Becker K, Köhrer K, WGGC Team, DeRGA community, Schiffer P, Thomma BPHJ and Rovenich H (2023) High quality genome assembly and annotation (v1) of the eukaryotic terrestrial microalga Coccomyxa viridis SAG 216-4. Peer Community Journal DOI: 10.24072/pcjournal.447
Snelders NC, Rovenich H, Thomma BPHJ (2022). Microbiota manipulation through the secretion of effector proteins is fundamental to the wealth of lifestyles in the fungal kingdom. FEMS Microbiology Reviews 46: fuac022.