title: Dual Role of a SAS10/C1D Family Protein in Ribosomal RNA Gene Expression and Processing Is Essential for Reproduction in Arabidopsis thaliana.
abstract: In eukaryotic cells, ribosomal RNAs (rRNAs) are transcribed, processed, and assembled with ribosomal proteins in the nucleolus. Regulatory mechanisms of rRNA gene (rDNA) transcription and processing remain elusive in plants, especially their connection to nucleolar organization. We performed an in silico screen for essential genes of unknown function in Arabidopsis thaliana and identified Thallo (THAL) encoding a SAS10/C1D family protein. THAL disruption caused enlarged nucleoli in arrested embryos, aberrant processing of precursor rRNAs at the 5' External Transcribed Spacer, and repression of the major rDNA variant (VAR1). THAL overexpression lines showed de-repression of VAR1 and overall reversed effects on rRNA processing sites. Strikingly, THAL overexpression also induced formation of multiple nucleoli per nucleus phenotypic of mutants of heterochromatin factors. THAL physically associated with histone chaperone Nucleolin 1 (NUC1), histone-binding NUC2, and histone demethylase Jumonji 14 (JMJ14) in bimolecular fluorescence complementation assay, suggesting that it participates in chromatin regulation. Furthermore, investigation of truncated THAL proteins revealed that the SAS10 C-terminal domain is likely important for its function in chromatin configuration. THAL also interacted with putative Small Subunit processome components, including previously unreported Arabidopsis homologue of yeast M Phase Phosphoprotein 10 (MPP10). Our results uncovering the dual role of THAL in transcription and processing events critical for proper rRNA biogenesis and nucleolar organization during reproduction are the first to define the function of SAS10/C1D family members in plants.
authors: Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan.|Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, Academia Sinica and National Chung Hsing University, Taichung, Taiwan.|Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung, Taiwan.
authors: Ying-Jiun C
authors: YC
authors: Chen
authors: Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan.
authors: Huei-Jing
authors: HJ
authors: Wang
authors: Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan.|Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, Academia Sinica and National Chung Hsing University, Taichung, Taiwan.|Biotechnology Center, National Chung-Hsing University, Taichung, Taiwan.
authors: Guang-Yuh
authors: http://orcid.org/0000-0003-3459-1331
authors: GY
authors: Jauh
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000096:biosynthesis* / Q000235:genetics; D002466:Cell Nucleolus / Q000235:genetics; D002843:Chromatin / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D006570:Heterochromatin / Q000235:genetics; D006657:Histones / Q000235:genetics; D056484:Jumonji Domain-Containing Histone Demethylases / Q000096:biosynthesis / Q000235:genetics; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics; D012335:RNA, Ribosomal / Q000096:biosynthesis* / Q000235:genetics; D012098:Reproduction / Q000235:genetics; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins; D002843:Chromatin; D006570:Heterochromatin; D006657:Histones; D009687:Nuclear Proteins; D012335:RNA, Ribosomal; D014157:Transcription Factors; C549618:JMJ14 protein, Arabidopsis; D056484:Jumonji Domain-Containing Histone Demethylases