A02

Diversity in the impact of karrikin signalling A02 on arbuscular mycorrhiza development

The arbuscular mycorrhiza (AM) symbiosis between most land plants and glomeromycotan fungi increases plant mineral nutrition and therefore has great potential for sustainable agriculture. The development of this symbiosis is largely controlled by the plant. The role of several plant genes involved in AM formation is conserved across species and among di- and monocotyledons.

In contrast, we have identified a striking qualitative difference in the requirement of the karrikin receptor complex (KAI2-MAX2) for AM development among divergent plant species. In some species, the fungus does not attach to the surface of kai2 mutant roots (Gutjahr et al., 2015; Meng et al., 2022), while it can pass the epidermis of kai2 mutants in other species (unpublished), to then colonize the root cortex at reduced levels as compared to the wild-type. The karrikin receptor complex perceives smoke-derived karrikins, which induce germination of fire-following plants.

These are thought to mimic endogenous, yet unknown plant hormones, tentatively called KAI2-ligands (KL). They bind to the nucleo-cytoplasmatically localised α/β-fold hydrolase receptor KAI2, which interacts with the F-box protein MAX2 in the nucleus to mediate ubiquitination and degradation of the karrikin signalling repressor SMAX1. smax1 mutants of different plant species. display increased root colonization, indicating that the the difference lies in the requirement for the KAI2-MAX2 module.

With this project, we want to unravel the molecular basis of the divergent requirement of the KAI2-MAX2 module for AM symbiosis in divergent plant species.

Principal Investigator: Prof. Dr. Caroline Gutjahr, Max Planck Institute of Molecular Plant Physiology