The overexpression of rice ACYL-COA-BINDING PROTEIN4 improves salinity tolerance in transgenic rice

Increased salinity, as consequence of the ongoing climate change, has a significant impact on crop production worldwide. The overexpression of rice ACYL-COA-BINDING PROTEIN4 (OsACBP4) protects transgenic rice and Arabidopsis from salinity stress, while OsACBP4-RNAi lines were more susceptible than the vector control (VC) and wild type (WT). The overexpression of AtACBP2, the Arabidopsis OsACBP4 homologue, also conferred salinity protection in transgenic rice and Arabidopsis. When OsACBP4 expression was investigated using ß-glucuronidase (GUS) reporter fusion, OsACBP4pro::GUS expression was induced after salt treatment of transgenic rice seedlings. Electrophoretic mobility shift assays verified that four salinity-responsive elements in the OsACBP4 5’-flanking region interacts with nuclear protein from salt-treated rice. RNA-sequencing and qRT-PCR on salt-treated rice OsACBP4-overexpressors (OEs), revealed an upregulation of all five genes encoding acyl-CoA synthase, essential in fatty acid elongation, over the controls. Furthermore, GC–MS analysis showed differences in fatty acid content between the leaves of the OsACBP4-OEs and the controls. Taken together, OsACBP4 may play a role in salinity responses by regulating lipid metabolism through binding acyl-CoA esters in vegetative tissues as recombinant OsACBP4 was subsequently confirmed to bind long-chain acyl-CoA esters in isothermal titration calorimetry assays.