Concerted expression of a cell cycle regulator and a metabolic enzyme from a bicistronic transcript in plants

Nat Plants. 2019 Feb;5(2):184-193. doi: 10.1038/s41477-019-0358-3. Epub 2019 Feb 8.


Eukaryotic mRNAs frequently contain upstream open reading frames (uORFs), encoding small peptides that may control translation of the main ORF (mORF). Here, we report the characterization of a distinct bicistronic transcript in Arabidopsis. We analysed loss-of-function phenotypes of the inorganic polyphosphatase TRIPHOSPHATE TUNNEL METALLOENZYME 3 (AtTTM3), and found that catalytically inactive versions of the enzyme could fully complement embryo and growth-related phenotypes. We could rationalize these puzzling findings by characterizing a uORF in the AtTTM3 locus encoding CELL DIVISION CYCLE PROTEIN 26 (CDC26), an orthologue of the cell cycle regulator. We demonstrate that AtCDC26 is part of the plant anaphase promoting complex/cyclosome (APC/C), regulates accumulation of APC/C target proteins and controls cell division, growth and embryo development. AtCDC26 and AtTTM3 are translated from a single transcript conserved across the plant lineage. While there is no apparent biochemical connection between the two gene products, AtTTM3 coordinates AtCDC26 translation by recruiting the transcript into polysomes. Our work highlights that uORFs may encode functional proteins in plant genomes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5' Untranslated Regions
  • Acid Anhydride Hydrolases / genetics*
  • Acid Anhydride Hydrolases / metabolism
  • Anaphase-Promoting Complex-Cyclosome / genetics
  • Anaphase-Promoting Complex-Cyclosome / metabolism
  • Arabidopsis / cytology
  • Arabidopsis / genetics*
  • Arabidopsis / growth & development
  • Arabidopsis Proteins / genetics*
  • Arabidopsis Proteins / metabolism
  • CRISPR-Cas Systems
  • Cytoplasm / metabolism
  • Gene Expression Regulation, Plant
  • Mutation
  • Open Reading Frames
  • Plants, Genetically Modified
  • Polyribosomes / genetics
  • Polyribosomes / metabolism


  • 5' Untranslated Regions
  • Arabidopsis Proteins
  • Anaphase-Promoting Complex-Cyclosome
  • Acid Anhydride Hydrolases
  • At2g11890 protein, Arabidopsis