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First published online October 23, 2009; 10.1105/tpc.109.069757 The Plant Cell 21:3296-3314 (2009) © 2009 American Society of Plant Biologists
Cotranslational Proteolysis Dominates Glutathione Homeostasis to Support Proper Growth and Development[C],[W]
a Centre National de la Recherche Scientifique, Institut des Sciences du Végétal, Unité Propre de Recherche2355, Protein Maturation, Cell Fate, and Therapeutics, F-91198 Gif-sur-Yvette cedex, France 1 Address correspondence to carmela.giglione{at}isv.cnrs-gif.fr.
The earliest proteolytic event affecting most proteins is the excision of the initiating Met (NME). This is an essential and ubiquitous cotranslational process tightly regulated in all eukaryotes. Currently, the effects of NME on unknown complex cellular networks and the ways in which its inhibition leads to developmental defects and cell growth arrest remain poorly understood. Here, we provide insight into the earliest molecular mechanisms associated with the inhibition of the NME process in Arabidopsis thaliana. We demonstrate that the developmental defects induced by NME inhibition are caused by an increase in cellular proteolytic activity, primarily induced by an increase in the number of proteins targeted for rapid degradation. This deregulation drives, through the increase of the free amino acids pool, a perturbation of the glutathione homeostasis, which corresponds to the earliest limiting, reversible step promoting the phenotype. We demonstrate that these effects are universally conserved and that the reestablishment of the appropriate glutathione status restores growth and proper development in various organisms. Finally, we describe a novel integrated model in which NME, protein N-
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