Rice DEAD-box RNA helicase OsRH53 has negative impact on Arabidopsis response to abiotic stresses

DEAD-box RNA helicases (RHs) play key roles in the regulation of RNA metabolism at the posttranscriptional level. In this study, the expression patterns under abiotic stresses and the functions of a rice (Oryza sativa) RH, OsRH53, in stress response were determined using transgenic Arabidopsis plants. The level of OsRH53 decreased upon abiotic stress treatment, including, drought, salt, cold, and UV stress, and by abscisic acid (ABA). Although OsRH53 contains a putative chloroplast transit peptide at the N-terminal end, confocal analysis of OsRH53-GFP fusion proteins transiently expressed in tobacco leaves revealed that OsRH53 is localized to the nucleus. OsRH53-expressing transgenic Arabidopsis displayed retarded germination and reduced growth under high salinity or dehydration stress but not under cold stress. OsRH53 negatively affected the growth and cotyledon greening of seedlings upon ABA application by activating the genes related to ABA signaling such as ABI3 and ABI4. The ability of OsRH53 to recover growth-defect phenotype of Escherichia coli mutant, and both in vitro and in vivo base pair-breaking ability confirmed that OsRH53 harbors RNA chaperone activity. Collectively, these results suggest that OsRH53 negatively affects plant abiotic stress responses via modulating RNA metabolism through its RNA chaperone activity.