During her PhD studies, Sofie Jin Vistisen Christiansen investigated how the legume Lotus japonicus interacts with root-associated bacteria. By combining synthetic microbial communities with natural soils from Japan, she explored how plant genes and nutrient conditions shape bacterial colonization. Using fluorescently labelled bacteria, she visualized where different strains colonize outside and inside plant roots.

Her work revealed that mutations in genes involved in phosphate regulation and root hair development alter both plant health and the colonization behaviour of the bacteria. These findings provide new insights into how plants balance beneficial and harmful bacteria, and how nutrient availability influences plant-microbe interactions.

The PhD study was completed at Molecular Biology and Genetics, Faculty of Natural Sciences, Aarhus University.

This summary was prepared by the PhD student.

Time: Thursday, 11 December 2025 at 13:00
Place: Building 1871, room 120, Lecture Theatre Nucleus, Molecular Biology and Genetics, Aarhus University, Universitetsbyen 81, 8000 Aarhus C.
Title of PhD thesis: Plant genetic control of root-microbe interactions: linking nutrient homeostasis, symbiosis, and microbiome assembly in Lotus japonicus
Contact information: Sofie Jin V. Christiansen, e-mail: sjc@mbg.au.dk, tel.: +45 21283505
Members of the assessment committee:
Professor Kåre Lehmann Nielsen, Department of Chemistry and Bioscience, Aalborg University, Denmark
Professor Akos Kovács, Institute of Biology, Leiden University, The Netherlands
Associate Professor Kasper Munch (chair), Molecular Biology and Genetics – Bioinformatics Research Centre, Aarhus University, Denmark
Main supervisor: Professor Jens Stougaard, Molecular Biology and Genetics, Aarhus University, Denmark
Co-supervisor: 
Professor Stig U. Andersen, Molecular Biology and Genetics, Aarhus University, Denmark
Dr Francesca Tedeschi, Molecular Biology and Genetics, Aarhus University, Denmark
Language: The PhD dissertation will be defended in English

The defence is public.
The PhD thesis is available for reading at the Graduate School of Natural Sciences/GSNS, Ny Munkegade 120, building 1521, 8000 Aarhus C