Reduced Expression of APUM24, Encoding a Novel rRNA Processing Factor, Induces Sugar-Dependent Nucleolar Stress and Altered Sugar Responses in Arabidopsis thaliana. Issue 1 (14th December 2017)

• Record Type: Journal Article
• Authors: Maekawa, Shugo; Ishida, Tetsuya; Yanagisawa, Shuichi
• Is Part Of: The Plant Cell. Volume 30:Issue 1(2018)
• Page Start: 209
• Page End: 227
• Publication Date: 2017-12-14
• DOI: 10.1105/tpc.17.00778
• Languages: English
• ISSNs: 1040-4651

Abstract

Abstract : The essential rRNA processing factor APUM24 functions in removal of internal transcribed spacer 2, and reduction of APUM24 causes sugar-dependent rRNA processing defects and nucleolar stress. Abstract: Ribosome biogenesis is one of the most energy-consuming events in the cell and must therefore be coordinated with changes in cellular energy status. Here, we show that the sugar-inducible gene ARABIDOPSIS PUMILIO PROTEIN24 ( APUM24 ) encodes a Pumilio homology domain-containing protein involved in pre-rRNA processing in Arabidopsis thaliana . Null mutation of APUM24 resulted in aborted embryos due to abnormal gametogenesis and embryogenesis, whereas reduced expression of APUM24 caused several phenotypes characteristic of ribosome biogenesis or function-related mutants. APUM24 interacted with other pre-rRNA processing factors and a putative endonuclease for the removal of the internal transcribed spacer 2 (ITS2) of pre-rRNA in the nucleolus. The APUM24-containing complex also interacted with ITS2, and reduced APUM24 expression caused the overaccumulation of processing intermediates containing ITS2. Thus, APUM24 likely functions as an ITS2 removal-associated factor. Most importantly, the apum24 knockdown mutant was hypersensitive to highly concentrated sugar, and the mutant showed sugar-dependent overaccumulation of processing intermediates and nucleolar stress (changes in nucleolar size). Furthermore, reduced APUM24 expression diminished sugar-induced promotion of leaf and root growth. Hence, a breakdown in the coordinated expression of ribosome biogenesis-related genes with energy status may induce nucleolar stress and disturb proper sugar responses in Arabidopsis.