A rice sitl1 mutant induced by gamma-ray irradiation shows enhanced
insensitivity to salinity via reduced accumulation in Na+ and Mg2+
Abstract
Salinity stress is one of the most important abiotic stress factors
affecting rice (Oryza sativa) production worldwide. Using a forward
genetics approach, we isolated a salt insensitive TILLING line 1 (sitl1)
rice mutant from a gamma-ray irradiated TILLING population. This sitl1
mutant line showed increased salinity tolerance due to reduced Mg2+ and
Na+ uptake in root and shoot tissues and in the xylem sap. Whole genome
resequencing and RNA-sequencing analyses identified a single nucleotide
T insertion in exon 5 of Os01g47460 (putative metal ion transporter)
with the CorA-like ZntB cation transfer domain (OsMGT1). Transient
expression of the OsMGT1-sGFP fusion protein in rice protoplasts showed
OsMGT1 was localized to the plasma membrane. Expression analysis of
various tissues and at different growth stages showed that the OsMGT1
was mainly expressed in roots and leaf tissues as an early response to
salinity stress. Complementation and overexpression assays in the yeast
(Saccharomyces cerevisiae) CM66 strain and wild type showed that the
OsMGT1 protein possessed both Mg2+ and Na+ transport activity. Taken
together, the mutation of the OsMGT1 gene in the sitl1 mutant reduced
the transport abilities of both Na+ and Mg2+ conferring salinity
insensitivity in rice.