Kaemoka’s group studies arbuscular mycorrhizal (AM) symbiosis. AM symbiosis started shortly after plant terrestrialization and is currently conserved in more than 70% of land plants. The elucidation of AM symbiosis is important for understanding plant physiology, ecology, and evolution. They aim to understand how plants and AM fungi find and recognize each other and focus on the signaling molecules. They are also trying to establish new fundamental experimental systems for AM symbiosis research, including axenic culture and transfection.

Main Achievements:

1. Axenic culture of AM fungi

AM fungi supply inorganic nutrients to plants in exchange for carbon sources from plants. They play important roles in terrestrial ecosystems and are used in agriculture as biofertilizers. However, AM fungi cannot proliferate alone because they do not produce spores without host plants, which disturbs both basic research and agricultural applications of AM fungi. They focused on the finding that cocultivation of AM fungi with some bacteria induces the spore formation in AM fungi and isolated branched-chain fatty acids from the bacteria as the compounds inducing spore formation. We also found that palmitoleic acid induces more spores and that palmitoleic acid-induced spores can colonize host plants and form the next generation of spores (Kameoka et al., 2019. Nat. Microbiol). Based on these results and our following studies (Sugiura et al., 2020. PNAS; Tanaka et al., 2022. Commun. Biol.), we established the first AM fungus axenic culture system, which will be a breakthrough for the production of AM fungus inoculums.

2. Transcriptomic atlas of AM fungi

AM fungi differentiate a variety of hyphal structures and spores; however, the differences in their physiological functions are largely unknown. They revealed the structure-specific transcriptome of AM fungi using the SMART-seq2 method, which enables analysis of the transcriptome from trace samples. In particular, they focused on the exchange of nutrients, the main function of AM symbiosis, and showed the roles of each structure in the transport and metabolism of nutrients (Kameoka et al., 2019. Plant Cell Physiol.). These findings provide a comprehensive dataset to advance our understanding of the transcriptional dynamics of fungal nutrition in this symbiotic system.