A rice DEAD-box protein, OsRH36, can complement an Arabidopsis atrh36 mutant, but cannot functionally replace its yeast homolog Dbp8p.

DEAD-box proteins comprise a large family and function in RNA metabolism. Although DEAD-box proteins are highly conserved among eukaryotes, little is known about the role of DEAD-box proteins in rice. In this study, we identified a rice DEAD-box protein, OsRH36, and demonstrated that OsRH36 and AtRH36 are functional orthologs. OsRH36 was expressed ubiquitously throughout the plant and the OsRH36-GFP fusion protein was localized to the nucleus and nucleolus. Furthermore, functional complementation tests among three homologous DEAD-box protein genes indicated that OsRH36 can restore segregation distortion in the Arabidopsis atrh36-1 mutant, but cannot complement the lethal phenotype in the yeast dbp8p mutant. Moreover, mutation of osrh36 also led to defective transmission of the osrh36 allele, as shown for the atrh36 mutants of Arabidopsis. Previously, we have shown that AtRH36 is involved at an early stage of rRNA maturation and is required for synchronous development of female gametophytes in Arabidopsis. Therefore, we suggest that OsRH36 is required for rRNA biogenesis and megagametogenesis in rice, consistent with the function of AtRH36 in Arabidopsis.