Rice Na+-Permeable Transporter OsHAK12 Mediates Shoots Na+ Exclusion in Response to Salt Stress

Abstract

Soil salinity has become a major stress factor that reduces crop productivity worldwide. Sodium (Na+) toxicity in a number of crop plants is tightly linked with shoot Na+ overaccumulation, thus Na+ exclusion from shoot is crucial for salt tolerance in crops. In this study, we identified a member of the high-affinity K+ transport family (HAK), OsHAK12, which mediates shoots Na+ exclusion in response to salt stress in rice. The Oshak12 mutants showed sensitivity to salt toxicity and accumulated more Na+ in the xylem sap, leading to excessive Na+ in the shoots and less Na+ in the roots. Unlike typical HAK family transporters that transport K+, OsHAK12 is a Na+-permeable plasma membrane transporter. In addition, OsHAK12 was strongly expressed in the root vascular tissues and induced by salt stress. These findings indicate that OsHAK12 mediates Na+ exclusion from shoot, possibly by retrieving Na+ from xylem vessel thereby reducing Na+ content in the shoots. These findings provide a unique function of a rice HAK family member and provide a potential target gene for improving salt tolerance of rice.

Rice potassium transporter OsHAK18 mediates phloem K+loading and redistribution

“…Considering that some KUP/HAK/KT transporters were shown to be permeable to Na + (Zhang et al, 2021; Zhang et al, 2019), we also determined whether OsHAK18 mediated cell Na + absorption using the Na + -sensitive yeast B31. AtHKT1;1, which mediates Na + uptake, was used as a positive control.…”

“…Some members in this subgroup, such as OsHAK12 and AtKUP9, had been reported to perform the functions quite different from OsHAK18. In contrast with OsHAK18, OsHAK12 was shown to be not permeable to K + but mediate Na + uptake when expressed in yeast (Zhang et al, 2021). AtKUP9, an ER-localized KUP/HAK/KT transporter, was reported to mediate K + and auxin efflux from ER to cytoplasm in root quiescent center (QC) cells to maintain meristem activity, which is essential to root growth under K + deficiency (Zhang et al, 2020).…”

“…OsHAK21also contributes to maintenance of K + homeostasis as a K + transporter under salt stress, whose expression was induced by NaCl but not K + deficiency (He et al, 2019; Shen et al, 2015). OsHAK12 was shown to be permeable to Na + but not K + , and possibly retrieved NaCl from xylem vessel, thereby reducing NaCl content in shoots (Zhang et al, 2021).…”

Overexpression of ZmDUF1644 from Zoysia matrella enhances salt tolerance in Arabidopsis thaliana

“…Salt stress disturbed the intracellular ion homeostasis and decreased the metabolic activity of plants caused by ionic stress (Zhang et al 2021a;Zhang et al 2021b). In addition, excessive Na + /K + also caused plant cellular dehydration, membrane dysfunction, and ion toxicity (Gupta et al 2021;Zhang et al 2021c). To alleviate ion stress, plants mainly reduce salt ion concentration in the cytoplasm through reduced uptake (Sofy et al 2020), increased exclusion (Wei et al 2022), or compartmentalized salt ions in the vesicles (Lang et al 2017).…”

Rice potassium transporter OsHAK18 mediates phloem K+ loading and redistribution

“…Considering that some KUP/HAK/KT transporters were shown to be permeable to Na + (Zhang et al, 2019(Zhang et al, , 2021, we also determined whether OsHAK18 mediated cell Na + absorption using the Na + -sensitive yeast B31 (MATa, his3, leu2, ura3, trp1, ade2, ena1::HIS3::ena4, nha1::LEU2). AtHKT1;1, which mediates Na + uptake, was used as a positive control.…”