Piriformospora indica and Arabidopsis thaliana Mutualism in Modeled Microgravity Conditions: A Model for Plant-Fungal Interactions in Spaceflight

Understanding how plant–microbe interactions function in spaceflight is critical for developing sustainable bioregenerative life support systems. As a model system, investigating plant-microbe interactions in microgravity also provides insight into human-microbiome interactions and infectious disease by exploring the ecological balance between mutualism, commensalism, parasitism, and competition in stressful environments. We investigated the mutualism between Piriformospora indica and Arabidopsis thaliana in modeled microgravity using ground-based analogs. P. indica enhances A. thaliana root branching, biomass accumulation, and leaf pigmentation. The fungus was cultured axenically, sporulated without a plant host, and retained infectivity in clinostat conditions. These findings establish the feasibility of this model system for spaceflight and provide a foundation for assessing plant-fungal symbioses in altered gravity environments.