EhEm1, a novel Em-like protein from Eutrema halophilum, confers tolerance to salt and drought stresses in rice

Late embryogenesis abundant (LEA) proteins play active and significant roles in stress resistance of plants. In this work, a novel Em-like gene, EhEm1, was isolated and characterized from salt cress. Bioinformatic analysis revealed that the EhEm1 protein contained three 20-mer conserved motifs (N-motif, M-motif, and C-motif), shared high homology with Em proteins from other species, and was categorized into group 1 LEA proteins. The EhEm1 was expressed only in the roots during the seedling period, and its transcript levels were significantly increased in all examined tissues during the flowering and mature periods. Transcription of EhEm1 was dramatically induced by salt, dehydration, abscisic acid (ABA), and cold stresses in young seedlings. The EhEm1 protein could prevent the lactate dehydrogenase (LDH) enzyme from inactivation caused by salt and desiccation treatments, and contribute to the stabilization of LDH activity. The sensitivity of transgenic rice seeds to exogenous ABA showed that EhEm1 functioned in an ABA-dependent signal pathway in response to abiotic stresses. Compared with wild type (WT) plants, EhEm1-overexpressing rice enhanced tolerance to salt and drought stresses based on better germination performances, higher survival rates, reduced chlorophyll damage, more accumulation of proline, less accumulation of malondialdehyde, and increased peroxidase activity under salt and drought stresses. The EhEm1-overexpressing rice showed less yield loss than did WT rice under salt and drought stresses. In addition, overexpression of the EhEm1 gene in rice could up-regulate transcript levels of several stress-responsive genes, including OsCDPK6, OsCDPK9, OsCDPK13, and rab16a under both salt and drought conditions, indicating that enhanced salt and drought tolerance of transgenic rice could be involved in the upregulation of OsCDPK genes. Thus, this work provides an insight into the tolerance of plants to abiotic stresses.