Heterologous overexpression of Pandanus odorifer Asparagine synthetase 1 (PoASN1) confers enhanced salinity tolerance in Escherichia coli and Rice.

Salinity stress is one of the major environmental factors drastically affecting crop productivity all over the world. At a biochemical level, salinity stress results in the production and accumulation of osmoprotectants, which serve as a mechanism for survival. The halophyte Pandanus odorifer (Forssk.) Kuntze grows in the wild, mainly along the seashore in the tropical and subtropical Pacific Oceans. Previously, we reported that the upregulated expression of asparagine synthetase (PoASN1) (EC 6.3.5.4) and the accumulation of the osmolyte asparagine conferred salt tolerance to the P. odorifer. Here, we focused on understanding the PoASN1 gene structure, enzymatic characteristics, regulatory mechanism and function via its overexpression in E. coli and Oryza sativa. In this study, expression analysis revealed that the PoASN1 gene was inducible only beyond 500 mM NaCl. Remarkably, overexpression of PoASN1 resulted in enhanced salinity survival of E. coli (up to 500 mM) and rice (up to 250 mM) because of osmolyte glycine betaine and asparagine, respectively, implying that glutamine-hydrolyzing PoASN1 plays a critical function in salinity tolerance.