Molecular cloning and functional analysis of a salt-induced gene encoding an RNA-binding protein in alfalfa

Based on the sequence of an expressed sequence tag of alfalfa (Medicago sativa L. cv. Zhongmu-1), a full-length sequence of 1,551 nucleotides was isolated using RACE-PCR techniques. This gene (MsRBP) was predicted to encode a protein of 409 amino acids, which contained three RNA recognition motifs comprising highly conserved RNA-binding domains at the N-terminus. Sequence analysis indicated that the C-terminus of MsRBP was rich in proline and glutamine residues. Subcellular location analysis suggested that MsRBP preferentially localized in the nucleus. Real-time fluorescent quantitative PCR analysis showed that the transcript level of MsRBP was upregulated after treating with 20 % polyethylene glycol (PEG6000), 100 mu M abscisic acid, or 300 mM NaCl. Compared with the wild-type plant, transgenic Arabidopsis plants overexpressing MsRBP displayed retarded germination and root growth under salt stress. The results suggested that MsRBP may play a negative role in salt stress regulation of alfalfa.