Proposed Mechanism For Regulation Of H2o2-Induced Programmed Cell Death In Plants By Binding Of Cytochrome C To 14-3-3 Proteins

Programmed cell death (PCD) is crucial for development and homeostasis of all multicellular organisms. In human cells, the double role of extra-mitochondrial cytochrome c in triggering apoptosis and inhibiting survival pathways is well reported. In plants, however, the specific role of cytochrome c upon release from the mitochondria remains in part veiled yet death stimuli do trigger cytochrome c translocation as well. Here, we identify an Arabidopsis thaliana 14-3-3 iota isoform as a cytosolic cytochrome c target and inhibitor of caspase-like activity. This finding establishes the 14-3-3 iota protein as a relevant factor at the onset of plant H2O2-induced PCD. The in vivo and in vitro studies herein reported reveal that the interaction between cytochrome c and 14-3-3 iota exhibits noticeable similarities with the complex formed by their human orthologues. Further analysis of the heterologous complexes between human and plant cytochrome c with plant 14-3-3 iota and human 14-3-3 epsilon isoforms corroborated common features. These results suggest that cytochrome c blocks p14-3-3 iota so as to inhibit caspase-like proteases, which in turn promote cell death upon H2O2 treatment. Besides establishing common biochemical features between human and plant PCD, this work sheds light onto the signaling networks of plant cell death.