The Key to Mn Homeostasis in Plants: Regulation of Mn Transporters.

Plants only require small amounts of manganese (Mn) for healthy growth, but Mn concentrations in soil solution vary from sub-micromolar to hundreds of micromolar across the growth period. Therefore, plants must deal with large Mn concentration fluctuations, but the molecular mechanisms underlying how plants cope with low and high Mn concentrations are poorly understood. In this Opinion we discuss the role of Mn transporters in the uptake, distribution, and detoxification of Mn in response to changes in Mn concentrations through their regulation at the transcriptional and protein levels, mainly focusing on rice, an Mn-tolerant and -accumulating species. We also propose mechanisms involved in the hyperaccumulation of Mn and future prospects for studying this specific trait.