Abstract
Molybdenum (Mo) is an essential trace element which is an electron donor and/or acceptor in Mo requiring enzymes. We previously isolated MOT1, the first molybdate transporter in eukaryotes, from Arabidopsis thaliana.
In this study, we found a low Mo accumulation Lotus japonica mutant by screening EMS-mutagenized seeds. Based on the genome analysis, Lotus has four genes that are closely related to MOT1. By sequencing theses putative Mo transporters in mutant, we found that there is a single nucleotide substitution (G876 to A876) in ST53 (LjMOT1) gene, a MOT1 like gene. This substitution changes amino acid Met to stop codon. To confirm the low Mo phenotype is due to the mutation in LjMOT1, the mutant was transformed with wild type LjMOT1 genomic fragment including promoter. Several independent transgenic plants were generated and the Mo concentrations in leaves of the transgenic lines were about 4 times higher than mutant. The mutant does not exhibit defect in nodulation and transcript accumulation is not much affected by nodulation. These data demonstrated that LjMOT1 is a major Mo transporter of Lotus for taking up Mo from soil, but not involved in the symbiosis.
