Abstract
Programmed cell death (PCD) is crucial in development, stress responses and homeostasis in all multicellular organisms. In plants, homologs of most major apoptosis regulators in animals have not been found and molecular mechanisms for regulation and execution of PCD are mostly unknown in plants. Ectopic expression of mammalian inhibitor of apoptosis proteins (IAPs) has recently been shown to affect plant PCD, suggesting possible presence of unknown functional IAP homologs in plants. By applying an improved motif searching method, we recently identified a novel gene family including Arabidopsis thaliana IAP like-protein1 and 2, which contains conserved domains similar to BIR domains of IAP (Higashi et al., 2005). We here report identification of a novel Arabidopsis gene with a mitochondrial localization signal, AtSmac, in which the IAP binding motif of the mammalian apoptosis regulator Smac/DIABLO was conserved. Possible physiological functions of AtSmac will be discussed.
