A Magnesium Transporter OsMGT1 Plays a Critical Role in Salt Tolerance in Rice

Abstract

Salt stress is one of the major factors limiting rice (Oryza sativa) production globally. Although several transporters involved in salt tolerance have been identified in rice, the mechanisms regulating their transport activity are still poorly understood. Here, we show evidence that a rice Mg transporter OsMGT1 is required for salt tolerance probably by regulating transport activity of OsHKT1;5, a key transporter for the removal of Na + from the xylem sap at the root mature zone. Knockout of OsMGT1 did not affect total Na uptake, but increased Na concentration in the shoots and xylem sap, resulting in a significant increase in salt sensitivity at low external Mg 2+ concentration (20-200 mM). However, such differences were abolished at a higher Mg 2+ concentration (2 mM), although the total Na uptake was not altered. OsMGT1 was expressed in both the roots and shoots, but only that in the roots was moderately up-regulated by salt stress. Spatial expression analysis revealed that OsMGT1 was expressed in all root cells of the root tips but was highly expressed in the pericycle of root mature zone. OsMGT1 was also expressed in the phloem region of basal node, leaf blade, and sheath. When expressed in Xenopus laevis oocytes, the transport activity of OsHKT1;5 was enhanced by elevating external Mg 2+ concentration. Furthermore, knockout of OsHKT1;5 in osmgt1 mutant background did not further increase its salt sensitivity. Taken together, our results suggest that Mg 2+ transported by OsMGT1 in the root mature zone is required for enhancing OsHKT1;5 activity, thereby restricting Na accumulation to the shoots.

Plastic transport systems of rice for mineral elements in response to diverse soil environmental changes

“…Mg uptake seems to be mediated by members belonging to the Mitochondrial RNA Splicing 2/Magnesium Transporter (MRS2/MGT) family however, so far, only OsMGT1 (OsMRS2‐2) has been functionally characterised (Chen et al , ). OsMRS2‐8 in the roots was upregulated under upland conditions (Figs S5a, S6a), probably in response to high Mg in soil solution (Fig.…”

A rice really interesting new gene H2‐type E3 ligase, OsSIRH2‐14, enhances salinity tolerance via ubiquitin/26S proteasome‐mediated degradation of salt‐related proteins

“…Under salinity stress, an ion imbalance, such as the accumulation of Na + , directly reduces carbon fixation and biomass production in plants. Additionally, K + can counteract Na + stress; thus, the potential of plants to tolerate salinity is dependent on their K + nutrition (Cha‐Um, Supaibulwattana, & Kirdmanee, ; Chen et al, ; Fakhrfeshani, Shahriari‐Ahmadi, Niazi, Moshtaghi, & Zare‐Mehrjerdi, ; Hoang et al, ; Yamamoto, Sawada, Shim, Usui, & Fujihara, ). For this reason, membrane integrity, Na + and K + concentrations, and the ratio between Na + and K + are key parameters that differentiate sensitive and tolerant rice cultivars during salinity stress (Hoang et al, ).…”

Physiological networks governing salinity tolerance potentials inGossypium hirsutumgermplasm

“…For example, intracellular Ca 2+ plays an important role in the activation of the SOS signaling pathway that controls cellular Na + homeostasis through Ca 2+ -mediated protein phosphorylation (Chinnusamy et al, 2004). Mg 2+ is an activator of HKT-type transporters such as HKT1 during the facilitation of Na + influx to the roots and its recirculation in the phloem (Chen et al, 2017).…”