In legumes, the establishment of symbioses with arbuscular mycorrhizal fungi and nitrogen-fixing bacteria share a common signalling pathway. One of the shared components is a calcium and calmodulin dependant protein kinase predicted to perceive and transduce the calcium signals generated upon perception of the symbiotic signals. The removal of the autoinhibitory domain that negatively regulates the kinase activity in Medicago truncatula, results in a constitutively-active form, inducing symbiotic responses in the absence of bacterial signals. Here, the heterologous production and partial purification of DMI3 variant as a tool for identifying substrates potentially involved in nodulation or mycorrhization was described.

Key words: Medicago truncatula, CCaMK, heterologous protein expression.