Spatial regulation of rice D14L for pre-symbiotic perception of beneficial fungi

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A key event in the evolution of higher life on earth is the transition of plant life from water to land. To explore the terrestrial environment plants had to develop strategies for the acquisition of soil nutrients with initially primitive root precursors. Ever since, plants have lived in symbioses with nutrient-delivering beneficial fungi. Today, the arbuscular mycorrhizal (AM) symbiosis is the most commonly occurring beneficial plant-fungal interaction on earth, contributing to plant fitness, plant biodiversity and global nutrient cycles. Yet, we are only beginning to unveil the molecular processes leading to mutual recognition in the rhizosphere. Colonization of plant roots by AM fungi requires the reciprocal exchange of diffusible molecules before fungal attachment to the root surface occurs. Chitin-related compounds secreted by AM fungi trigger plant molecular and developmental responses. Receptor kinase proteins detect these fungal molecules in the extracellular space and initiate a cellular reprogramming leading to a change in root system development. Mutational analyses showed that these receptor kinases are indeed required for development of AM symbioses but appear not to be essential. How plants perceive these prevalent beneficial fungi has therefore still been an unanswered question.My group has found that an intracellular alpha/beta hydrolase type protein, called DWARF 14 LIKE (D14L) is crucial for fungal perception by rice. In our recent Science publication we report our finding that the deletion of this gene from the rice genome rendered the plant unable to sense the fungus. Interestingly, the protein has additional roles in detecting the smoke constituent karrikin and in mediating developmental responses to light. It is evolutionarily conserved and may have therefore served similar functions in early terrestrial plants. The recognition of the fungus by the root and the subsequent establishment of primary contact involves distinct root tissue and cell types. The precise coordination of signaling events in space and time is thus essential for the successful development of AM symbioses. With this proposal we wish to determine where in the root tissue (relative to the approaching fungus) the protein needs to be present, and by magnifying onto the subcellular level, where within the cell the protein functions in initiating signal transduction and what are the respective 'molecular translations' of signalling.Given the central role of D14L in a variety of responses to environmental stimuli elucidating the tissue/cell type contributing to the signaling is vital for understanding coordination and specificity of this general and ancient plant symbiosis.