Molecular cloning and characterization of the soybean DEAD-box RNA helicase gene induced by low temperature and high salinity stress

A novel gene encoding a DEAD-box RNA helicase designated as GmRH was isolated from soybean. Amino acid sequence alignment and phylogenetic tree analysis revealed a close relationship between GmRH and other orthologous DEAD-box RNA helicases from other plant species. Structural motif analysis revealed that the bipartite lysine rich nuclear localization signal (NLS) is present in the N-terminal variable region of GmRH and that there are ten conserved motifs found in DEAD-box RNA helicase proteins. Southern blot analysis revealed the presence of 2 copies of GmRH in the soybean genome. Northern blot analysis demonstrated that the RNA expression of the GmRH was induced during low temperature or high salinity stress, but not by the exogenous application of abscisic acid or drought stress. Subcellular localization studies showed that GmRH((1-355))-GFP is localized in the nucleus, whereas GmRH((130-355))-GFP is localized both in the cytoplasm and in the nucleus. This provides the evidence that the N-terminal region predicted as NLS is essential for nuclear targeting of the GmRH protein in the plant cell. Purified GST-GmRH recombinant protein was shown to unwind dsRNA independent of ATP in vitro. Here, we propose that GmRH plays an important role in RNA processing during low temperature and high salinity stresses in plants. (C) 2009 Elsevier B.V. All rights reserved.