Identification, and Functional and Expression Analyses of the CorA/MRS2/MGT-Type Magnesium Transporter Family in Maize

Abstract

Magnesium (Mg(2+)) is an essential macronutrient for plant growth and development, and the CorA/MRS2/MGT-type Mg(2+) transporters play important roles in maintaining Mg(2+) homeostasis in plants. Although the MRS2/MGT genes have been identified in two model plant species, Arabidopsis and rice, a comprehensive analysis of the MRS2/MGT gene family in other plants is lacking. In this work, 12 putative MRS2/MGT genes (ZmMGT1- ZmMGT12) were identified in maize and all of them were classified into five distinct subfamilies by phylogenetic analysis. A complementation assay in the Salmonella typhimurium MM281 strain showed that five representatives of the 12 members possess Mg(2+) transport abilities. Inhibition of ZmMGT protein activity using the hexaamminecobalt (III) (Co-Hex) inhibitor indicated that the ZmMGT protein mediated both low-affinity and high-affinity Mg(2+) transport in maize. A semi-quantitative reverse transcription-PCR (RT-PCR) analysis revealed that eight genes were constitutively expressed in all of the detected tissues, with one being specifically expressed in roots and three having no detectable expression signals. A quantitative RT-PCR analysis showed that some ZmMGT members displayed differential responses to Mg(2+) deficiency and aluminum (Al) stress. Furthermore, root growth inhibition and Mg(2+) accumulation analyses in two maize inbred lines, which conferred different levels of Al tolerance, revealed that ZmMGT proteins contributed to the Al resistance of the Al tolerance genotype. We hypothesize that ZmMGT family members function as Mg(2+) transporters and may play a role in linking Mg(2+) deficiency and Al stress responses. Our results will be valuable in a further analysis of the important biological functions of ZmMGT members in maize.

Identification of QTLs for grain yield and other traits in tropical maize under Striga infestation

“…Plants acquire magnesium needed for growth and development from the environment and distribute within the plants in the ionic form via Mg 2+ - permeable transporters [ 67 ]. The Mg 2+ transporters mediate Mg 2+ uptake, translocation, and sequestration into cellular storage compartments [ 68 , 69 ]. Furthermore, the gene model GRMZM2G085113 ( qgy-3 ) associated with grain yield under Striga infestation encodes the terminal ear1 protein, te1.…”

Magnesium Transporter MGT6 Plays an Essential Role in Maintaining Magnesium Homeostasis and Regulating High Magnesium Tolerance in Arabidopsis

“…However, the molecular mechanisms for Mg transport and homeostasis in plant cells remain largely unknown. Genomes of many plants such as Arabidopsis , rice, and maize, encode homologs of the bacterial CorA-type proteins referred to as MGTs/MRS2s ( Li et al, 2001 , 2016 ; Saito et al, 2013 ). Some members of the MGT family have been functionally characterized, but the physiological roles of these transporters are not well understood.…”

Relative association of Rubisco with manganese and magnesium as a regulatory mechanism in plants

“…To date, only one mutation in Arabidopsis ( pam71 ) has been identified that influences Mn 2+ uptake into chloroplasts (Schneider et al ) and only one Mg 2+ transporter/channel has been identified in the chloroplast envelope membrane (MRS2‐11) (Finazzi et al ). A vacuolar Mn 2+ transporter MTP8 enhances tolerance and accumulation of Mn 2+ in rice (Chen et al ), and several plasma membrane members of the CorA/MRS2/MGT type Mg 2+ transporters seem to play roles in maintaining Mg 2+ homeostasis in Arabidopsis , rice, and maize (Li et al ). Certainly, cellular regulation of Mn 2+ and Mg 2+ activities warrants further investigation.…”