A root-expressed magnesium transporter of the MRS2/MGT gene family in Arabidopsis thaliana allows for growth in low-Mg2+ environments.
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.
Gebert
Michael
M
Institut für Zelluläre und Molekulare Botanik, Universität Bon, D-53115 Bon, Germany.
Meschenmoser
Karoline
K
Svidová
Sona
S
Weghuber
Julian
J
Schweyen
Rudolf
R
Eifler
Karolin
K
Lenz
Henning
H
Weyand
Katrin
K
Knoop
Volker
V
D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D005816:Genetic Complementation Test; D008274:Magnesium / Q000378:metabolism*; D005810:Multigene Family; D016254:Mutagenesis, Insertional; D009154:Mutation; D010802:Phylogeny; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics
D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; D004269:DNA, Bacterial; D018749:RNA, Plant; C036483:T-DNA; D008274:Magnesium