Soybean Inositol Polyphosphate 5-Phosphatase 8 Confers Salt Tolerance by Reducing Sodium Influx Through Inositol 1,4,5-Trisphosphate Signalling.

Evidence suggests that the metabolism of inositol and its derivatives may be involved in various biological processes including salt tolerance, but there has been limited understanding. Ectopic expression of Gs5PTase8, an inositol polyphosphate 5-phosphatase cloned from wild soybean (Glycine soja), significantly enhanced salt tolerance in cultivated soybean (Glycine max). In this follow up study, the overexpression of Gs5PTase8 was shown to improve salt tolerance in transgenic Arabidopsis thaliana, soybean hairy roots and composite plants, by preventing sodium (Na+) accumulation and maintaining lower sodium/potassium (Na+/K+) ratios in plants under salt stress. Additionally, the interactions between Gs5PTase8 and its substrate, inositol 1,4,5-trisphosphate (IP3), were investigated for their role in enhancing salt tolerance. Overexpressing Gs5PTase8 reduced IP3 contents, probably due to its 5-phosphatase activity. Moreover, external supplementation of IP3 could restore the Na+ accumulation in the Gs5PTase8-overexpressing tobacco BY-2 cells experiencing salt stress. The proteomic data obtained by data-independent acquisition implied that the degradation of IP3 or phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) by Gs5PTase8 may maintain the ion homoeostasis of plants under salt stress by influencing the cytosolic calcium (Ca2+) signalling and the salt overly sensitive pathways.