OsRH17 (Os05g0110500) is located on chromosome 5 of the rice genome and consists of 10 exons. The full-length cDNA shows that OsRH17 encodes a putative protein that consists of 591 amino acid residues with a calculated molecular weight of 67 kDa and an isoelectric point of 9.56. Searching for conserved domains revealed that amino acids 22 to 248 and 295 to 443 in the OsRH17 protein represent two typical conserved domains, DEADc (PF00270) and HELICs (helicase superfamily C-terminal domain, PF00271) (Fig. 1A), which are composed of nine conserved RH motifs. OsRH17 contained amino acid residues D-E-A-D in motif II (Fig. 1B). Thus, we hypothesized that OsRH17 is a member of the DEAD-box class of RNA helicases. Sequence comparisons revealed that this OsRH17 was highly conserved in plant evolution. The predicted OsRH17 protein shares more than 85% amino acid sequence identity with homologous proteins from several monocots such as Zea mays and Sorghum bicolor and approximately 60% identity with proteins from dicot species including Populus trichocarpa, Vitis vinifera, Ricinus communis, Medicago truncatula, Glycine max, and A. thaliana. The relative homology of OsRH17 to proteins from different species revealed their evolutionary relationships to a certain degree