Required for early signal transduction events leading to endosymbiosis. Acts early in a signal transduction chain leading from the perception of Nod factor to the activation of calcium spiking. Also involved in mycorrhizal symbiosis. May be involved in the regulation of the calcium channel responsible for calcium spiking by mobilizing another cation, and thereby altering the membrane potential. Interacts (via c-terminus) with CNGC15A, CNGC15B and CNGC15C (via N-terminus). The Nod factor has no effect on these interactions, implying that the complex is maintained after activation. Mainly expressed in roots and nodules. Also detected in pods, flowers, leaves, and stems. Not induced after bacterial or Nod factor treatment. The N-terminal domain (1-76) is sufficient, but not required, to target DMI1 to the nucleus. Loss of microbial symbioses. Undergoes typical root hairs growth deformation in response to Nod factors, but exhibits no calcium spiking and nodule formation. Belongs to the castor/pollux (TC 1.A.1.23) family.