Required for mycorrhizal symbiosis. Expressed in roots, leaves, stems and panicles. Not induced by mycorrhizal colonization. Defective in mycorrhizal symbiosis. Can restore nodulation but not rhizobial infection to a Medicago truncatula dmi1 mutant, but cannot restore mycorrhizal or rhizobial symbiosis in a Ljpollux mutant of Lotus japonicus. Belongs to the castor/pollux (TC 1.A.1.23) family.