Abstract
The model legume Lotus japonicus develops nitrogen-fixing root nodules as a result of an interaction with soil bacteria Mesorhizobium loti. The organogenic process resulting in nodule development is triggered by the bacterial microsymbiont, but genetically controlled by the host plant genome. Non-nodulating (Nod-) mutant Ljsym3 was unable to initiate nodule development with M. loti NZP2235. However the Ljsym3-1 alelle can develop, with low frequency, nodule like structures after inoculation with the M. loti TONO. Ljsym3 does not develop mycorrhizal symbiosis. Aside from the symbiotic phenotypes, all Ljsym3 mutant alelles developed morphological alterations such as short seedpods with aborted embryos.
To identify the Ljsym3 gene, map based cloning was carried out. On the genetic map of Lotus, the sym3 locus is located on the short arm of chromosome I, close to the top. Genotyping of 822 mutant plants identified markers delimiting the sym3 locus to 29kb.
