The urea transporter DUR3 contributes to rice production under nitrogen-deficient and field conditions

Nitrogen is one of the most important elements for plant growth, and urea is one of the most frequently used nitrogen fertilizers worldwide. Besides the exogenously-supplied urea to the soil, urea is endogenously synthesized during secondary nitrogen metabolism. Here, we investigated the contribution of a urea transporter, DUR3, to rice production using a reverse genetic approach combined with localization studies. Tos17 insertion lines for DUR3 showed a 50% yield reduction in hydroponic culture, and a 26.2% yield reduction in a paddy field, because of decreased grain filling. Because shoot biomass production and shoot total N was not reduced, insertion lines were disordered not only in nitrogen acquisition but also in nitrogen allocation. During seed development, DUR3 insertion lines accumulated nitrogen in leaves and could not sufficiently develop their panicles, although shoot and root dry weights were not significantly different from the wild-type. The urea concentration in old leaf harvested from DUR3 insertion lines was lower than that in wild-type. DUR3 promoter-dependent beta-glucuronidase (GUS) activity was localized in vascular tissue and the midribs of old leaves. These results indicate that DUR3 contributes to nitrogen translocation and rice yield under nitrogen-deficient and field conditions.