Abstract
Symbiosis between legume plants and Rhizobium bacteria is established on mutual complex interactions between two symbiotic partners. Recently, a number of host plant genes involved in early stages of symbiosis were identified by positional cloning from model legume Lotus japonicus. However, host plant genes involved in the mutual interactions in the later stages are still totally unknown. Our aim is to isolate the genes specifically involved in functional symbiosis by molecular genetic approaches with L. japonicus. A fix- mutant, Ljsym105 was isolated from L. japonicus MG-20 regenerated from hypocotyls induced calli. Ljsym105 showed nitrogen deficiency symptoms upon inoculation with M.loti Tono in nitrogen free condition and formed pink nodules with acetylene reduction activity less than half of wild type. Genetic analysis revealed that Ljsym105 was monogenic and recessive, and genetic linkage analysis using DNA markers indicated that Ljsym105 locates on upper portion of chromosome 4 of Lotus japonicus.
