Abstract
A number of leguminous mutants blocked at the early stages of rhizobial infection are also defective in mycorrhizal colonization. The mutated genes of such mutants compose a common symbiosis pathway (CSP) that controls both rhizobial and mycorrhizal endosymbioses. During infection, microsymbionts release infection signal molecules which evoke periodical change of Ca2+ concentration (Ca spiking), in the root hair cells of host plants. Most of the CSP genes are positioned upstream of Ca spiking and required for induction of it. On the other hand, CCaMK is downstream of Ca spiking and a candidate of a decoder for symbiosis specific Ca signals, although molecular mechanisms of Ca signaling through CSP remains to be elucidated. Our recent studies with gain-of-function CCaMK demonstrated that activation of CSP is prerequisite for successful infection of endosymbionts. The possible role of CSP in acceptance of infection by microsymbionts will be discussed.
