OsDISMO1: A Novel Transporter for Molybdenum Distribution in Rice Shoots

Molybdenum (Mo) is an essential micronutrient for plants, forming the Mo cofactor (Moco) necessary for molybdoenzyme activity. While only a single type of molybdate transporter (MOT) has been identified in plants, other Mo transporters remain unknown. In this study, we identified a novel Mo transporter gene, OsDISMO1 (Oryza sativa Distributor of Molybdenum 1), through the characterization of a high Mo grain mutant in rice. Gene mapping of the mutant and the phenotype of knockout mutants demonstrated that OsDISMO1 is responsible for the observed mutant phenotype. Mo concentration analysis in various leaf tissues of three-week-old seedlings revealed higher Mo levels in the young leaves of the mutant compared to the wild type Hitomebore (HB), while the flag leaf of the mutant had lower Mo levels than the HB. OsDISMO1 promoter-GUS analysis indicated expression in the vascular bundles of shoots, particularly in the phloem. Additionally, a GFP-fused OsDISMO1 protein was localised to the endoplasmic reticulum (ER) membrane in rice protoplasts. The ability of OsDISMO1 to transport Mo was confirmed through heterologous expression in Saccharomyces cerevisiae. These findings suggest that OsDISMO1 is a Mo transporter, facilitating the movement of Mo from old to new or source tissues.