摘要Magnesium(Mg2+),an essential structural component of chlorophyll,is absorbed from the soil by roots and transported to shoots to support photosynthesis in plants.However,the molecular mechanisms underlying root-to-shoot Mg2+translocation remain largely unknown.We describe here the identification of four plasma membrane(PM)-localized transporters,named Mg2+release transporters(MGRs),that are critical for root-to-shoot Mg transport in Arabidopsis.Functional complementation assays in a Mg2+-uptake-defi-cient bacterial strain confirmed that these MGRs conduct Mg2+transport.PM-localized MGRs(MGR4,MGR5,MGR6,and MGR7)were expressed primarily in root stellar cells and participated in the xylem loading step of the long-distance Mg2+transport process.In particular,MGR4 and MGR6 played a major role in shoot Mg homeostasis,as their loss-of-function mutants were hypersensitive to low Mg2+but tolerant to high Mg2+conditions.Reciprocal grafting analysis further demonstrated that MGR4 functions in the root to determine shoot Mg2+accumulation and physiological phenotypes caused by both low-and high-Mg2+stress.Taken together,our study has identified the long-sought transporters responsible for root-to-shoot Mg2+translocation in plants.