Abstract
Leguminous plants are unique in their ability to form mutually beneficial root-microbe associations with rhizobial bacteria and arbuscular mycorrhizal (AM) fungi. Recent genetic studies in model legumes have revealed the existence of common symbiosis pathway (CSP) that is essential for both root nodule (RN) and AM symbioses. Among the host plant genes located in CSP, calcium calmodulin-dependent protein kinase (CCaMK) is thought to be a putative decoder for microsymbionts-induced Ca2+ signals and play a central role in rhizobial/mycorrhizal infections and nodule organogenesis. However, it remains unknown how CCaMK is activated in response to symbiotic partners. To elucidate the activation mechanisms of CCaMK and involvement of its functional domains in the activation processes, we carried out a detailed complementation analysis of Lotus ccamk mutant with various truncated or amino-acid substituted CCaMKs. Based on our study, we propose models for CCaMK activation during RN or AM symbioses.
