Molecular characterization of two plant BI-1 homologues which suppress Bax-induced apoptosis in human 293 cells

Planta. 2003 Jan;216(3):377-86. doi: 10.1007/s00425-002-0879-1. Epub 2002 Oct 8.


To date, few homologues of animal programmed cell death (PCD) regulators have been identified in plants. Among these is the plant Bax Inhibitor-1 (BI-1) protein, which possesses, like its human counterpart, the ability to suppress Bax-induced lethality in yeast cells. As the role of BI-1 in the regulation of plant PCD remains to be elucidated, we cloned BnBI-1 and NtBI-1 from cDNA libraries of oilseed rape ( Brassica napus L.) and tobacco ( Nicotiana tabacum L.). The analysis of the deduced amino acid sequences of BnBI-1 and NtBI-1 indicated that these proteins share a relatively high level of identity with other plant BI-1 proteins (73-95%) as well as with animal BI-1 proteins (26-42%). Comparative analysis with other available plant BI-1 proteins allowed the establishment of a structural model presenting seven transmembrane domains. Moreover, transient co-transfection of Bax with BnBI-1 or NtBI-1 in human embryonic kidney 293 cells revealed that both proteins can substantially inhibit apoptosis induced by Bax overexpression. Localization studies were also conducted using stable transformation of tobacco BY-2 cells and Saccharomyces cerevisiae, or transient expression in tobacco leaves, with the fusion protein BnBI-1GFP under control of the cauliflower mosaic virus 35S promoter. All transformants showed a fluorescence pattern of distribution typical of an endoplasmic reticulum (ER) protein. Results from differential permeabilization experiments in BY-2 cells expressing BnBI-1GFP also showed that the C-terminus is located on the cytosolic side of the ER. Taken altogether, our results suggest that BI-1 is evolutionarily conserved and could act as a key regulator of a death pathway common to plants and animals.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Apoptosis / genetics*
  • Apoptosis / physiology
  • Apoptosis Regulatory Proteins
  • Brassica napus / genetics*
  • Brassica napus / metabolism
  • Cell Line
  • Cells, Cultured
  • Cloning, Molecular
  • Endoplasmic Reticulum / genetics
  • Endoplasmic Reticulum / metabolism
  • Green Fluorescent Proteins
  • Humans
  • Kidney / cytology
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Membrane Proteins / genetics*
  • Membrane Proteins / metabolism
  • Molecular Sequence Data
  • Phylogeny
  • Proteins*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Sequence Analysis
  • Sequence Homology, Amino Acid
  • Tobacco / genetics*
  • Tobacco / metabolism


  • Apoptosis Regulatory Proteins
  • Luminescent Proteins
  • Membrane Proteins
  • Proteins
  • TMBIM6 protein, human
  • Green Fluorescent Proteins

Associated data

  • GENBANK/AF390555
  • GENBANK/AF390556