Death proteases: alive and kicking.

Two recent discoveries significantly add to our understanding of plant programmed cell death (PCD). Hatsugai et al. showed that cell death is dependent on proper proteasome functioning. Sundström et al. showed that the in vivo substrate of a type II metacaspase is associated with cell viability. Both findings are major breakthroughs within the plant PCD field and highlight that the plant cell death machinery apparently employs a wide range of structurally unrelated proteases that, surprisingly, show a caspase-like preference for specific (evolutionarily conserved) substrates.