Molecular cloning and characterization of an ASR gene from Cucumis sativus

Abstract

Abscisic acid-, stress- and ripening-induced (ASR) proteins are widely present in the plant kingdom and play important roles in different biological processes. However, no reports of ASR proteins are available in cucumber. In this study, an ASR gene (CsASR1) was identified and characterized from Cucumis sativus. CsASR1 exhibited a high content of disorder-promoting amino acids, indicating that it is an intrinsically disordered protein (IDP). CsASR1 protein was highly homologous to ASR proteins from other plant species. Expression of CsASR1 was induced by diverse abiotic stresses such as heat, PEG and NaCl, as well as by signaling molecules such as ABA and H2O2, suggesting a close relationship between CsASR1 and abiotic stress. Overexpression of CsASR1 could increase the tolerance against salinity and osmotic stress in E. coli. Transgenic Arabidopsis plants overexpressing CsASR1 exhibited higher germination rate than WT plants on MS medium containing various concentrations of NaCl. In addition, overexpression of CsASR1 in Arabidopsis resulted in significantly improved salt tolerance due to the increased activity of SOD and elevated transcripts of SOS3 and LEA4-5. Finally, CsASR1 could protect the activity of lactate dehydrogenase (LDH) from heat-induced inactivation. Taken together, our results demonstrate that CsASR1 plays an important role in abiotic stress tolerance, and it may function as an IDP to confer abiotic stress tolerance by protecting some stress-related proteins from inactivation under stress conditions.