A root-expressed magnesium transporter of the MRS2/MGT gene family in Arabidopsis thaliana allows for growth in low-Mg2+ environments

Plant Cell. 2009 Dec;21(12):4018-30. doi: 10.1105/tpc.109.070557. Epub 2009 Dec 4.

Abstract

The MRS2/MGT gene family in Arabidopsis thaliana belongs to the superfamily of CorA-MRS2-ALR-type membrane proteins. Proteins of this type are characterized by a GMN tripeptide motif (Gly-Met-Asn) at the end of the first of two C-terminal transmembrane domains and have been characterized as magnesium transporters. Using the recently established mag-fura-2 system allowing direct measurement of Mg(2+) uptake into mitochondria of Saccharomyces cerevisiae, we find that all members of the Arabidopsis family complement the corresponding yeast mrs2 mutant. Highly different patterns of tissue-specific expression were observed for the MRS2/MGT family members in planta. Six of them are expressed in root tissues, indicating a possible involvement in plant magnesium supply and distribution after uptake from the soil substrate. Homozygous T-DNA insertion knockout lines were obtained for four members of the MRS2/MGT gene family. A strong, magnesium-dependent phenotype of growth retardation was found for mrs2-7 when Mg(2+) concentrations were lowered to 50 microM in hydroponic cultures. Ectopic overexpression of MRS2-7 from the cauliflower mosaic virus 35S promoter results in complementation and increased biomass accumulation. Green fluorescent protein reporter gene fusions indicate a location of MRS2-7 in the endomembrane system. Hence, contrary to what is frequently found in analyses of plant gene families, a single gene family member knockout results in a strong, environmentally dependent phenotype.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics*
  • Arabidopsis / growth & development
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Cation Transport Proteins / genetics
  • Cation Transport Proteins / metabolism*
  • Cloning, Molecular
  • DNA, Bacterial / genetics
  • Gene Expression Regulation, Plant
  • Gene Knockout Techniques
  • Genetic Complementation Test
  • Magnesium / metabolism*
  • Multigene Family
  • Mutagenesis, Insertional
  • Mutation
  • Nicotiana / genetics
  • Phylogeny
  • Plant Roots / genetics
  • Plant Roots / growth & development*
  • Plant Roots / metabolism
  • Plants, Genetically Modified / genetics
  • RNA, Plant / genetics
  • Saccharomyces cerevisiae / metabolism

Substances

  • Arabidopsis Proteins
  • Cation Transport Proteins
  • DNA, Bacterial
  • RNA, Plant
  • T-DNA
  • Magnesium