ATR3 encodes a diflavin reductase essential for Arabidopsis embryo development

New Phytol. 2010 Jul;187(1):67-82. doi: 10.1111/j.1469-8137.2010.03254.x. Epub 2010 Apr 12.


*The Arabidopsis genome possesses two confirmed Cytochrome P450 Reductase (CPR) genes, ATR1 and ATR2, together with a third putative homologue, ATR3, which annotation is questionable. *Phylogenetic analysis classified ATR3 as a CPR-like protein sharing homologies with the animal cytosolic dual flavin reductases, NR1 and Fre-1, distinct from the microsomal CPRs, ATR1 and ATR2. Like NR1 and Fre-1, ATR3 lacks the N-terminal endoplasmic reticulum (ER) anchor domain of CPRs and is localized in the cytoplasm. Recombinant ATR3 in plant soluble extracts was able to reduce cytochrome c but failed to reduce the human P450 CYP1A2. *Loss of ATR3 function resulted in early embryo lethality indicating that this reductase activity is essential. A yeast 2-hybrid screen identified a unique interaction of ATR3 with the homologue of the human anti-apoptotic CIAPIN1 and the yeast Dre2 protein. *This interaction suggests two possible roles for ATR3 in the control of cell death and in chromosome segregation at mitosis. Consistent with these results, the promoter of ATR3 is activated during cell cycle progression. Together these results demonstrated that ATR3 belongs to the NR1 subfamily of diflavin reductases whose characterized members are involved in essential cellular functions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis / cytology
  • Arabidopsis / embryology*
  • Arabidopsis / enzymology*
  • Arabidopsis / genetics
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Cell Cycle
  • Cell Nucleus / enzymology
  • Cytochrome P-450 CYP1A2 / metabolism
  • Cytochromes c / metabolism
  • Embryonic Development* / genetics
  • Gene Expression Regulation, Developmental
  • Gene Expression Regulation, Plant
  • Humans
  • Intracellular Signaling Peptides and Proteins / chemistry
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Molecular Sequence Data
  • Oxidation-Reduction
  • Oxidoreductases / chemistry
  • Oxidoreductases / genetics
  • Oxidoreductases / metabolism*
  • Protein Binding
  • Protein Transport
  • Seeds / cytology
  • Seeds / embryology*
  • Seeds / enzymology*


  • Arabidopsis Proteins
  • CIAPIN1 protein, human
  • Intracellular Signaling Peptides and Proteins
  • Cytochromes c
  • ATR3 protein, Arabidopsis
  • Oxidoreductases
  • CYP1A2 protein, human
  • Cytochrome P-450 CYP1A2