Abstract
Legumes can establish symbiotic relationships with rhizobia and mycorrhizae. The two different symbiosis systems are regulated by host legume genes, which belong to common symbiosis pathway (CSP). CASTOR and POLLUX, both of which encode potassium channels, have been identified as CSP genes in Lotus japonicus. On the other hand, only DMI1 has been identified as a symbiotic gene in Medicago truncatula. Like DMI1, mutations of CASTOR or POLLUX lead to Nod- and Myc- phenotypes. Despite their high similarity, single mutation of CASTOR or POLLUX caused symbiotic defective phenotypes, suggesting functional differentiation of CASTOR and POLLUX in Lotus.
Recently, MtCASTOR was isolated from the EST library of M. truncatula. Here we examined whether MtCASTOR plays a role in legume endosymtioses like its homologs DMI1, CASTOR and POLLUX. Additionally, cross-complementation analyses by expressing LjCASTOR and LjPOLLUX in dmi1 mutant of M. truncatula and to introduce M. truncatula DMI1 in Ljcastor and Ljpollux mutants of L. japonicus raised a novel model for functional evolution of CASTOR/POLLUX/DMI1.
