Similarly, the vector was linearized withSpeI and transcribed with T7 polymerase to generate a transcript of 127 nucleotides

Similarly, the vector was linearized withSpeI and transcribed with T7 polymerase to generate a transcript of 127 nucleotides. mediated by AtRH57 exists within the sugar-mediated ABA signaling. AtRH57 mutation and high Glc conditions additively caused a severe defect in small ribosomal subunit formation. The accumulation of abnormal pre-rRNA and resistance to protein synthesis-related antibiotics were observed inrh57mutants and in the wild-type Col-0 under high Glc conditions. These results suggested that AtRH57 plays an important role in rRNA biogenesis in Arabidopsis and participates in response to sugar involving Glc- and ABA signaling during germination and seedling growth. Keywords: RNA helicase, glucose-hypersensitive, abscisic acid, rRNA biogenesis, seedling growth, Arabidopsis thalianaseeds == Introduction == RNA helicases contain a large gene family found in all kingdoms (Linder, 2006). They are involved in many different cellular processes including ribosome biogenesis, RNA splicing, maturation, transport, editing, RNA interference, transcription, and mRNA stabilization and degradation (Cordinet al., 2006). The DEAD-box RNA helicases, by far the largest family of RNA helicases, has the sequence of Asp-Glu-Ala-Asp (D-E-A-D) in motif II (Linder and Jankowsky, 2011). In spite of the sequence similarity of DEAD-box RNA helicases within the core helicase regions, each DEAD-box protein is believed to play various key roles in plant development (Linder and Jankowsky, 2011). The proteins have been intensively studied in animals and P276-00 yeasts (Kemp and ImLer, 2009; Sahniet al., 2010) but only a few DEAD-box members have been identified in plants. In Arabidopsis, at least 120 members of the RNA helicases can be predicted using the TAIR database (http://www.arabidopsis.org/) and 58 DEAD-box RNA helicases have been identified thus far (Boudetet al., 2001). For instance, loss of the Arabidopsis DEAD-box protein ISE1 leads to abnormal mitochondria and enhanced cell-to-cell transport through plasmodesmata (Stonebloomet al., 2009). Arabidopsis DEAD-box proteins are required for the development of female gametophytes and play a role in rRNA biogenesis (Huanget al., 2010a; Liuet al., 2010). Recently, both AtRH3 and AtRH22 have been reported to affect chloroplast ribosome biogenesis (Asakuraet al., 2012; Chiet al., 2012). Aside from participating in different housekeeping processes, DEAD-box RNA helicase expression responds to various stresses (Owttrim, 2006; Vashisht and Tuteja, 2006). For example , ectopic expressions of the DEAD-box proteins PDH45 and PDH47 in peas have been respectively shown to confer salt resistance in tobacco (Sanan-Mishraet al., 2005) and promote responses to cold and salinity stresses in shoots and roots (Vashishtet al., 2005). In Arabidopsis, DEAD-box protein FLNA LOS4 has been demonstrated to be essential in exporting mRNA and regulating the expression of CBF factor under the condition of chilling stress (Gonget al., 2005). Three DEAD-box RNA helicases AtRH5, AtRH9, and AtRH25 also respond to multiple abiotic stresses in Arabidopsis (Kantet al., 2007; Kimet al., 2008). All these reports suggest a crucial role of plant helicases in stress tolerance; however , the response mechanism of RNA helicases to glucose (Glc), an important signaling factor affecting plant development has yet to be studied except that the UPF1 RNA helicase was found to alter sugar signaling in Arabidopsis (Yoineet al., 2006). DEAD-box proteins are diverse in structure and modulate various biological processes. Thus, the exact role of most plant DEAD-box proteins largely remains unclear and requires further studies. Previous studies have demonstrated that high Glc causes abscisic acid (ABA) accumulation, resulting P276-00 in a delay in germination and inhibition of the early P276-00 stages of seedling growth (Rollandet al., 2002; Gibson, 2005). Under various stress conditions, the arrest of seedling growth is also mediated by ABA (Lopez-Molinaet al., 2001). For gene regulation, high Glc may promote ABA biosynthesis and signaling gene expression and increase ABA content in the cell (Chenget al., 2002). Most of the ABA biosynthesis and ABA-insensitive mutants described thus far are insensitive to high Glc. A number of negative and positive regulators controlling ABA signaling pathways have recently been identified (Stoneet al., 2006; Buet al., 2009; Carvalhoet al., 2010; Huanget al., 2010b). Identification of these regulators emphasizes the complexity of the plant signaling transduction network. The present study reports the phenotypic and molecular analyses ofrh57mutants showing defects P276-00 in the Glc control of seedling growth, and gene expression. A feedback inhibition of ABA accumulation mediated by AtRH57 exists within the sugar-mediated ABA signaling. AtRH57 mutation and high amounts of Glc additively impair small ribosomal subunit formation. AtRH57 plays an important.