A node-based switch for preferential distribution of manganese in rice

Mineral nutrients, such as manganese, are required for the development of plants and their reproductive organs, but these can be toxic if accumulated at high concentrations. Therefore, plants must have a system for preferentially delivering an adequate amount of minerals to these organs for active growth and development, while preventing mineral overaccumulation in the face of changing environments. Here we show that a member of the Nramp transporter family, OsNramp3, functions as a switch in response to environmental Mn changes. OsNramp3 is constitutively expressed in the node, a junction of vasculatures connecting leaves, stems and panicles. At low Mn concentration, OsNramp3 preferentially transports Mn to young leaves and panicles. However, at high Mn concentration, the OsNramp3 protein is rapidly degraded within a few hours, resulting in the distribution of Mn to old tissues. Our results reveal the OsNramp3-mediated strategy of rice for adapting to a wide change of Mn in the environment.