title: Critical Issues in the Study of Magnesium Transport Systems and Magnesium Deficiency Symptoms in Plants.
abstract: Magnesium (Mg) is the second most abundant cation in living cells. Over 300 enzymes are known to be Mg-dependent, and changes in the Mg concentration significantly affects the membrane potential. As Mg becomes deficient, starch accumulation and chlorosis, bridged by the generation of reactive oxygen species, are commonly found in Mg-deficient young mature leaves. These defects further cause the inhibition of photosynthesis and finally decrease the biomass. Recently, transcriptome analysis has indicated the transcriptinal downregulation of chlorophyll apparatus at the earlier stages of Mg deficiency, and also the potential involvement of complicated networks relating to hormonal signaling and circadian oscillation. However, the processes of the common symptoms as well as the networks between Mg deficiency and signaling are not yet fully understood. Here, for the purpose of defining the missing pieces, several problems are considered and explained by providing an introduction to recent reports on physiological and transcriptional responses to Mg deficiency. In addition, it has long been unclear whether the Mg deficiency response involves the modulation of Mg2+ transport system. In this review, the current status of research on Mg2+ transport and the relating transporters are also summarized. Especially, the rapid progress in physiological characterization of the plant MRS2 gene family as well as the fundamental investigation about the molecular mechanism of the action of bacterial CorA proteins are described.
authors.affiliation: Graduate School of Agricultural and Life Sciences, the University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. anikoba@mail.ecc.u-tokyo.ac.jp.
authors.forename: Natsuko I
authors.initials: NI
authors.lastname: Kobayashi
authors.affiliation: Graduate School of Agricultural and Life Sciences, the University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. uktanoi@mail.ecc.u-tokyo.ac.jp.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Tanoi
mesh_terms: D001692:Biological Transport; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D002413:Cations, Divalent / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D008274:Magnesium / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D010944:Plants / Q000235:genetics / Q000378:metabolism*
chemical_list: D027682:Cation Transport Proteins; D002413:Cations, Divalent; D010940:Plant Proteins; D008274:Magnesium
keywords: MRS2 transporter; Mg deficiency; chlorosis; magnesium