Improved Salinity Tolerance of Rice Through Cell Type-Specific Expression of AtHKT1;1

Abstract

Previously, cell type-specific expression of AtHKT1;1, a sodium transporter, improved sodium (Na+) exclusion and salinity tolerance in Arabidopsis. In the current work, AtHKT1;1, was expressed specifically in the root cortical and epidermal cells of an Arabidopsis GAL4-GFP enhancer trap line. These transgenic plants were found to have significantly improved Na+ exclusion under conditions of salinity stress. The feasibility of a similar biotechnological approach in crop plants was explored using a GAL4-GFP enhancer trap rice line to drive expression of AtHKT1;1 specifically in the root cortex. Compared with the background GAL4-GFP line, the rice plants expressing AtHKT1;1 had a higher fresh weight under salinity stress, which was related to a lower concentration of Na+ in the shoots. The root-to-shoot transport of 22Na+ was also decreased and was correlated with an upregulation of OsHKT1;5, the native transporter responsible for Na+ retrieval from the transpiration stream. Interestingly, in the transgenic Arabidopsis plants overexpressing AtHKT1;1 in the cortex and epidermis, the native AtHKT1;1 gene responsible for Na+ retrieval from the transpiration stream, was also upregulated. Extra Na+ retrieved from the xylem was stored in the outer root cells and was correlated with a significant increase in expression of the vacuolar pyrophosphatases (in Arabidopsis and rice) the activity of which would be necessary to move the additional stored Na+ into the vacuoles of these cells. This work presents an important step in the development of abiotic stress tolerance in crop plants via targeted changes in mineral transport.

Amelioration of Soybean Plant from Saline-Induced Condition by Exopolysaccharide Producing <i>Pseudomonas</i>-Mediated Expression of High Affinity K⁺-transporter (HKT1) Gene

“…Besides, improved salinity tolerance through cell typespecific expression of AtHKT1;1 was observed in rice 38 . The over expression of Na + and K + permeable HvHKT2;1 transporter in both roots and shoots by low K + growth conditions, and in shoots by high Na + growth conditions leads to increased salt tolerance by reinforcing the salt including behaviour of barley 39 . Whereas Xue et al 40 found Nernstian shift in Na + channel transport properties in Arabidopsis root stellar cells of AtHKT1;1.…”

Grapevine and Arabidopsis cation-chloride cotransporters localise to the Golgi and trans-Golgi network and indirectly influence long-distance ion homeostasis and plant salt tolerance

“…Overexpression or ectopic expression of genes that are important for salt tolerance in plants can often improve plant growth under salt stress (for example, high affinity potassium transporters [HKTs; Plett et al, 2010;Munns et al, 2012], glutathione S-transferase [GST; Roxas et al, 1997], and chloride channels [CLCs; Wei et al, 2013]). Expression of VviCCC restored growth of the Atccc mutant to wild-type levels under salt stress but did not enhance growth beyond that of wild-type Col-0.…”

TsHKT1;2, a HKT1 Homolog from the Extremophile Arabidopsis Relative Thellungiella salsuginea, Shows K+ Specificity in the Presence of NaCl

“…An extraordinarily strong support for the importance of HKT-like proteins in mediating salinity stress tolerance has been provided by genetic and molecular studies in models (Sunarpi et al, 2005;Møller et al, 2009;Genc et al, 2010;Hauser and Horie, 2010;Plett et al, 2010;Qiu et al, 2011). In several cases, improved salinity tolerance has been associated with regions of genomes that included HKT-type transporters.…”