SummaryProgrammed Cell Death (PCD) plays a key role in defense and development of all multicellular organisms. PCD in animals and plants, however, show distinct features that involve phylum specific components. Here we identify KISS OF DEATH (KOD), a 25-amino-acid peptide of Arabidopsis thaliana, that regulates PCD during embryo development. KOD was isolated in a promoter trap line with specific expression of the reporter gene in suspensor cells.
The suspensor is a single file of 8 to 10 cells that support embryo delopment and then dies from PCD. Two mutant alleles and natural variants of KOD showed reduced PCD in the suspensor. In addition, over-expression of KOD in plant tissues activated a PCD sensitive to Bcl-2, Bax-inhibitor and the caspase inhibitor p35. The use of synthetic KOD confirmed that the peptide was the functional product , and its NMR analysis revealed a well-structured amphiphilic alpha-helix possibly involved in interactions with membranes. KOD represents the first member of a novel class of PCD regulators, among which it is the shortest sequence described thus far.
> GUS expression in the trap line 276S The globular-embryo is approx. 40 um large. (photo from Valérie Hecht).
TUNEL assay and KOD Structure. (A) Treatment of
Arabidopsis protoplasts with KOD peptide and variants. DNA fragmentation
was assayed using TUNEL. Mock and UV treatments used as negative and positive
controls, respectively. (B) Overlay of 22 calculated structures from NMR spectra. Nt,
N-terminus; Ct, C-terminus. Residues 9 to 21 fold into an alpha-helix, whereas the N-terminal region is disordered. (C) Model of the
amphiphilic helix with the two hydrophobic
ridges of 6 and 4 residues.
We are currently revising this work...
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