Arabidopsis S6 kinase mutants display chromosome instability and altered RBR1-E2F pathway activity

Rossana Henriques, Zoltán Magyar, Antonia Monardes, Safina Khan, Christine Zalejski, Juan Orellana, László Szabados, Consuelo De La Torre, Csaba Koncz, László BÖgre

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The 40S ribosomal protein S6 kinase (S6K) is a conserved component of signalling pathways controlling growth in eukaryotes. To study S6K function in plants, we isolated single- and double-knockout mutations and RNA-interference (RNAi)-silencing lines in the linked Arabidopsis S6K1 and S6K2 genes. Hemizygous s6k1s6k2/++ mutant and S6K1 RNAi lines show high phenotypic instability with variation in size, increased trichome branching, produce non-viable pollen and high levels of aborted seeds. Analysis of their DNA content by flow cytometry, as well as chromosome counting using DAPI staining and fluorescence in situ hybridization, revealed an increase in ploidy and aneuploidy. In agreement with this data, we found that S6K1 associates with the Retinoblastoma-related 1 (RBR1)-E2FB complex and this is partly mediated by its N-terminal LVxCxE motif. Moreover, the S6K1-RBR1 association regulates RBR1 nuclear localization, as well as E2F-dependent expression of cell cycle genes. Arabidopsis cells grown under nutrient-limiting conditions require S6K for repression of cell proliferation. The data suggest a new function for plant S6K as a repressor of cell proliferation and required for maintenance of chromosome stability and ploidy levels.

Original languageEnglish
Pages (from-to)2979-2993
Number of pages15
JournalEMBO Journal
Issue number17
Publication statusPublished - Sep 1 2010



  • E2F
  • S6 kinase
  • cell proliferation
  • chromosome instability
  • retinoblastoma

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)

Cite this

Henriques, R., Magyar, Z., Monardes, A., Khan, S., Zalejski, C., Orellana, J., Szabados, L., De La Torre, C., Koncz, C., & BÖgre, L. (2010). Arabidopsis S6 kinase mutants display chromosome instability and altered RBR1-E2F pathway activity. EMBO Journal, 29(17), 2979-2993.