Abstract
Molybdenum (Mo) is a transient element found in the cofactor of several prokaryotic and eukaryotic enzymes. During nodulation, the symbiotic interaction between legumes and soil-living bacteria, atmospheric nitrogen is reduced into ammonia by the nitrogenase, a Mo-containing bacterial enzyme. To investigate the requirements of Mo during nodulation, we set out to identify Mo transporters in L. japonicus. We searched L. japonicus database for homologous sequences of the A. thaliana Mo transporter MOT1 and identified four putative AtMOT1 orthologs (LjMOT1-4). An EMS mutant of L. japonicus, line 4-22, showing a dramatic reduction in its Mo content had previously been isolated. A mutation resulting in a early stop codon in the sequence of LjMOT1 was found in 4-22. Macroscopic nodulation phenotype as well as nitrogenase activity were investigated in this mutant and no significant differences were observed with wild-type plants, suggesting that low amounts of Mo are sufficient to sustain nodulation.
