Arabidopsis Type I Metacaspases Control Cell Death

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Science  03 Dec 2010:
Vol. 330, Issue 6009, pp. 1393-1397
DOI: 10.1126/science.1194980

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The Yin and Yang of Plant Caspases

The function of plant metacaspases, identified by limited sequence homology to the animal caspases that control cell death, has remained elusive. Coll et al. (p. 1393) have now elucidated the actions of two metacaspases in the small plant Arabidopsis. One metacaspase, AtMC1, promoted cell death, and the other, AtMC2, acted antagonistically to stall cell death. The results help to elucidate the mechanisms by which plants control cell survival during development and defend against pathogen attack.


Metacaspases are distant relatives of animal caspases found in protozoa, fungi, and plants. Limited experimental data exist defining their function(s), despite their discovery by homology modeling a decade ago. We demonstrated that two type I metacaspases, AtMC1 and AtMC2, antagonistically control programmed cell death in Arabidopsis. AtMC1 is a positive regulator of cell death and requires conserved caspase-like putative catalytic residues for its function. AtMC2 negatively regulates cell death. This function is independent of the putative catalytic residues. Manipulation of the Arabidopsis type I metacaspase regulatory module can nearly eliminate the hypersensitive cell death response (HR) activated by plant intracellular immune receptors. This does not lead to enhanced pathogen proliferation, decoupling HR from restriction of pathogen growth.

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