title: Two highly similar DEAD box proteins, OsRH2 and OsRH34, homologous to eukaryotic initiation factor 4AIII, play roles of the exon junction complex in regulating growth and development in rice.
abstract: BACKGROUND
  The exon junction complex (EJC), which contains four core components, eukaryotic initiation factor 4AIII (eIF4AIII), MAGO/NASHI (MAGO), Y14/Tsunagi/RNA-binding protein 8A, and Barentsz/Metastatic lymph node 51, is formed in both nucleus and cytoplasm, and plays important roles in gene expression. Genes encoding core EJC components have been found in plants, including rice. Currently, the functional characterizations of MAGO and Y14 homologs have been demonstrated in rice. However, it is still unknown whether eIF4AIII is essential for the functional EJC in rice.
  
  
  RESULTS
  This study investigated two DEAD box RNA helicases, OsRH2 and OsRH34, which are homologous to eIF4AIII, in rice. Amino acid sequence analysis indicated that OsRH2 and OsRH34 had 99 % identity and 100 % similarity, and their gene expression patterns were similar in various rice tissues, but the level of OsRH2 mRNA was about 58-fold higher than that of OsRH34 mRNA in seedlings. From bimolecular fluorescence complementation results, OsRH2 and OsRH34 interacted physically with OsMAGO1 and OsY14b, respectively, which indicated that both of OsRH2 and OsRH34 were core components of the EJC in rice. To study the biological roles of OsRH2 and OsRH34 in rice, transgenic rice plants were generated by RNA interference. The phenotypes of three independent OsRH2 and OsRH34 double-knockdown transgenic lines included dwarfism, a short internode distance, reproductive delay, defective embryonic development, and a low seed setting rate. These phenotypes resembled those of mutants with gibberellin-related developmental defects. In addition, the OsRH2 and OsRH34 double-knockdown transgenic lines exhibited the accumulation of unspliced rice UNDEVELOPED TAPETUM 1 mRNA.
  
  
  CONCLUSIONS
  Rice contains two eIF4AIII paralogous genes, OsRH2 and OsRH34. The abundance of OsRH2 mRNA was about 58-fold higher than that of OsRH34 mRNA in seedlings, suggesting that the OsRH2 is major eIF4AIII in rice. Both OsRH2 and OsRH34 are core components of the EJC, and participate in regulating of plant height, pollen, and seed development in rice.
authors.affiliation: Department of Life Sciences, National Central University, Jhongli District, Taoyuan City, 32001, Taiwan (ROC).
authors.forename: Chun-Kai
authors.initials: CK
authors.lastname: Huang
authors.affiliation: Department of Life Sciences, National Central University, Jhongli District, Taoyuan City, 32001, Taiwan (ROC).
authors.forename: Yi-Syuan
authors.initials: YS
authors.lastname: Sie
authors.affiliation: Department of Life Sciences, National Central University, Jhongli District, Taoyuan City, 32001, Taiwan (ROC).
authors.forename: Yu-Fu
authors.initials: YF
authors.lastname: Chen
authors.affiliation: Department of Life Sciences, National Central University, Jhongli District, Taoyuan City, 32001, Taiwan (ROC).
authors.forename: Tian-Sheng
authors.initials: TS
authors.lastname: Huang
authors.affiliation: Department of Life Sciences, National Central University, Jhongli District, Taoyuan City, 32001, Taiwan (ROC). chungan@cc.ncu.edu.tw.
authors.forename: Chung-An
authors.initials: CA
authors.lastname: Lu
mesh_terms: D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D053487:DEAD-box RNA Helicases / Q000235:genetics* / Q000378:metabolism; D039601:Eukaryotic Initiation Factor-4A / Q000145:classification / Q000235:genetics*; D005091:Exons / Q000235:genetics*; D020869:Gene Expression Profiling / Q000379:methods; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D012275:Oryza / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D011058:Pollen / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D011485:Protein Binding; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D007527:Isoenzymes; D008164:Luminescent Proteins; D010940:Plant Proteins; D039601:Eukaryotic Initiation Factor-4A; C000612500:DEAD-box ATP-dependent RNA helicase 2, Oryza sativa; C000612483:DEAD-box ATP-dependent RNA helicase 34, Oryza sativa; D053487:DEAD-box RNA Helicases
keywords: DEAD box RNA helicase; Eukaryotic initiation factor 4AIII (eIF4AIII); Exon junction complex (EJC); Rice (Oryza sativa)