Decoding calcium signals in Medicago truncatula

Calcium is an intracellular second messenger involved in the regulation of many processes in eukaryotes. In plants, changes in intracellular calcium concentration occur in response to biotic and abiotic stimuli. These specific changes in calcium concentration are called calcium signatures and are sensed by calcium decoders that contain two specific protein motifs: the EF-hand motif which binds a calcium ion, and the calmodulin binding domain that binds calmodulin which itself contains four EF-hand motifs. Plant symbiosis is one of the best studied models of plant Ca2+ signalling. About 80% of plants establish a beneficial association with arbuscular mycorrhizal (AM) fungi species, but only legumes such as Medicago truncatula, are able to establish a symbiosis with both AM fungi and nitrogen fixing rhizobial bacteria. The calcium and calmodulin dependent protein kinase (CCaMK) is a calcium decoder considered as the central regulator of the common symbiotic signalling pathway in plants. Using a synthetic biology approach, the calcium binding properties of the EFhand motifs will be studied using CCaMK as the model protein during symbiosis. Ultimately, these studies would provide the possibility of designing novel hybrid proteins that could be used in other calcium signalling pathways of other species