The Pre-rRNA Processing Complex in Arabidopsis Includes Two WD40-Domain- Containing Proteins Encoded by Glucose-Inducible Genes and Plant-Specific Proteins  Tetsuya Ishida, Shugo Maekawa, Shuichi Yanagisawa  Molecular Plant  Volume 9, Issue 2, Pages 312-315 (February 2016) DOI: 10.1016/j.molp.2015.11.003 Copyright © 2016 The Author Terms and Conditions

Figure 1 NuGWD1, Which Plays an Essential Role in Embryogenesis, Comprises the Pre-rRNA Processing Complex Together with SWA1 and Other Plant-Specific Proteins. (A) The nugwd1 allele. The position of the T-DNA insertion in SALK_052897 is indicated in the diagram of the structure of the NuGWD1 locus. The white and black boxes indicate untranslated and translated regions of exons, respectively. The translational start codon (ATG) and the stop codon (TAA) of the NuGWD1 coding region are indicated. Images of siliques of wild-type (ecotype Columbia) (WT) and nugwd1 Arabidopsis are also shown. (B) Transmission efficiency (TE) of the nugwd1 allele. TE = (number of heterozygotes/number of wild-type plants) × 100%. (C) Co-immunoprecipitation of NuGWD1 with SWA1. Immunoprecipitation (IP) of proteins in cell lysates from Arabidopsis T87 cells expressing NuGWD1-FLAG or both NuGWD1-FLAG and SWA1-MYC were performed using anti-MYC antibodies, and the proteins immunoprecipitated were subjected to western blot analysis using anti-MYC and anti-FLAG antibodies. (D) Co-expression network including NuGWD1 and SWA1. NuGWD1 and SWA1 are indicated in red, genes encoding proteins that were co-immunoprecipitated with SWA1 are indicated in pink, and genes encoding PCP1 and PCP2 are indicated in orange. PCP2 does not possess any known domain, while PCP1 contains an amino acid sequence that is somewhat homologous to that of a domain found in a yeast protein, Utp12. However, PCP1 is not the Arabidopsis homolog of Utp12, because PCP1 does not contain WD40 repeats that characterize Utp12. (E) Split-GFP-based bimolecular fluorescence complementation analysis of NuGWD1 with SWA1, PCP1, and PCP2. NuGWD1-nGFP was expressed alone or together with SWA1-cGFP, PCP1-cGFP, or PCP2-cGFP in tobacco leaf epidermal cells. FIB1-mCherry was used as a nucleolar marker. Images for green fluorescence were merged with images for fluorescence from FIB1-mCherry (Merged). DAPI staining indicates nucleoplasm. Scale bar represents 5 μm. (F) The RNA/DNA ratio (the amount of total RNA (mg) to the amount of DNA (mg) ratio) in T87 cells during the course of carbohydrate starvation and sugar treatments. The time when sugar was supplied was set to time 0. Glucose (Glc), sucrose (Suc), and mannitol (Man) were supplied to produce the final concentrations in the cultures as indicated. Data are shown as the means of biological triplicates ± SD. (G) Model for sugar-induced activation of rRNA synthesis and ribosome biogenesis. Sugar induces expression of genes encoding components of the t-UTP complex as well as PCP1 and PCP2. Since the t-UTP complex promotes transcription of rDNA and mediates processing of pre-rRNA through formation of a higher-ordered complex that includes other subcomplexes, the t-UTP complex might be a key complex for sugar-induced rRNA synthesis. Although it is currently unidentified which complex, the t-UTP or UTP B complex, includes PCP1 and PCP2, we show PCP1 and PCP2 as factors interacting with the t-UTP complex in this model. Since sugar induction of expression of genes encoding components of other subcomplexes of the pre-rRNA processing complex has not been established, such induction is indicated by a dashed line with an arrowhead. Molecular Plant 2016 9, 312-315DOI: (10.1016/j.molp.2015.11.003) Copyright © 2016 The Author Terms and Conditions