Abstract
Legumes can utilize atmospheric dinitrogen by highly coordinated symbiosis with rhizobium. Recently the legume genes involved in early nodulation process have been clarified with molecular genetic approach using the model legumes Lotus japonicus and Medicago trancatula. However, the mechanisms for later stages, infection process and nodule organogenesis, are still unknown. We report cloning and characterization of the LjSYM101 gene essential for the infection thread formation and subsequent nodule organogenesis.
Ljsym101 is a recessive and monogenic mutant with the infection process arrested in the middle part of the root hairs and nodulation blocked at the stage of bumps.
Linkage analysis allowed us to position the Ljsym101 locus within ~87kb region of the chromosome 5. We identified the causative gene by the sequence analysis and confirm it using 5 alleles of Ljsym101. LjSYM101 was predicted to code 1485aa. The expression was detected in uninfected roots and enhanced by inoculation with rhizobium.
