Characterization and map-based cloning of sym102 involved in nitrogen fixation activity in Lotus japonicus

Abstract

Leguminous plants form root nodules for symbiosis with soil bateria Rhizobia to fix dinitrogen in the atmosphere. To utilize symbiotic nitrogen fixation, it is indispensable to understand the molecular mechanism of nodulation process. Nitrogen fixation activity of rhizobium is controlled by the host plant under symbiotic condition. Fixation minus (Fix^-) mutants are good materials to identify the plant factors involved in development and maintenance of symbiotic nitrogen fixation.
In this study, we had analyzed a novel Fixation minus (Fix^-) mutant of Lotus japonicus Ljsym102. This mutant formed pale pink nodules with low nitrogen fixation activity and exhibited early senescence symptons in the nodule tissues. These preliminary observations showed Ljsym102 established a symbiotic association with Rhizobia but had defect to express effective nitrogen fixation activity. We report further characterization of Ljsym102 mutant and map-based cloning of its causal gene.