Lotus japonicus Sen1 Gene Is Crucial For Expression Of Symbiotic Nitrogen Fixing Activity

Abstract

⁶Max Planck Institute of Molecular Plant Physiology, University of Tokyo
A Lotus japonicus symbiotic mutant sen1 forms ineffective nodules under symbiotic condition, indicating that Sen1 is responsible for establishment of nitrogen-fixing symbiosis. To clarify the role of SEN1, Sen1 was identified by map-based cloning and expression profile was investigated. By linkage analysis, the Sen1 locus was delimited to a region of about 200kb on the chromosome 4. In one of 15 genes predicted in this region, a mutation was found by sequencing analysis. In further 3 more sen1 alleles, mutations were found in the same gene. Transformation of an entire gene into the sen1 could complement the mutant phenotype. Thus, we concluded that this gene is the Sen1. The Sen1 encodes a polypeptide of 266 amino acids, which contain 5 transmembrane regions. Expression of the gene was detected exclusively in nodules and was limited in the nodule infection cells.