Sugar-inducible expression of the nucleolin-1 gene of Arabidopsis thaliana and its role in ribosome synthesis, growth and development

• Published in: The Plant journal : for cell and molecular biology 2007-03, Vol.49 (6), p.1053-1063
• Main Authors: Kojima, Hisae, Suzuki, Takamasa, Kato, Takenori, Enomoto, Ken-ichi, Sato, Shusei, Kato, Tomohiko, Tabata, Satoshi, Sáez-Vasquez, Julio, Echeverría, Manuel, Nakagawa, Tsuyoshi, Ishiguro, Sumie, Nakamura, Kenzo
• Format: Article
• Language: English
• Subjects: Arabidopsis - genetics; Arabidopsis - physiology; Biochemistry; Biological and medical sciences; Botany; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation, Plant - physiology; Genes; Life Sciences; Nucleolin; Phosphoproteins - genetics; Phosphoproteins - metabolism; Plant growth. Development of the storage organs; Plant physiology and development; Proteins; Ribonucleic acid; ribosomal protein genes; ribosome synthesis; Ribosomes - metabolism; RNA; RNA-Binding Proteins - genetics; RNA-Binding Proteins - metabolism; snoRNP; Sucrose; Sugar; sugars; Vegetative apparatus, growth and morphogenesis. Senescence
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313X.2006.03016.x

Animal and yeast nucleolin function as global regulators of ribosome synthesis, and their expression is tightly linked to cell proliferation. Although Arabidopsis contains two genes for nucleolin, AtNuc-L1 is the predominant if not only form of the protein found in most tissues, and GFP-AtNuc-L1 fusion proteins were targeted to the nucleolus. Expression of AtNuc-L1 was strongly induced by sucrose or glucose but not by non-metabolizable mannitol or 2-deoxyglucose. Sucrose also caused enhanced expression of genes for subunits of C/D and H/ACA small nucleolar ribonucleoproteins, as well as a large number of genes for ribosomal proteins (RPs), suggesting that carbohydrate availability regulates de novo ribosome synthesis. In sugar-starved cells, induction of AtNuc-L1 occurred with 10 m m glucose, which seemed to be a prerequisite for resumption of growth. Disruption of AtNuc-L1 caused an increased steady-state level of pre-rRNA relative to mature 25S rRNA, and resulted in various phenotypes that overlap those reported for several RP gene mutants, including a reduced growth rate, prolonged lifetime, bushy growth, pointed leaf, and defective vascular patterns and pod development. These results suggest that the rate of ribosome synthesis in the meristem has a strong impact not only on the growth but also the structure of plants. The AtNuc-L1 disruptant exhibited significantly reduced sugar-induced expression of RP genes, suggesting that AtNuc-L1 is involved in the sugar-inducible expression of RP genes.