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RESEARCH PRODUCT

Post-Translational Modifications of Nuclear Proteins in the Response of Plant Cells to Abiotic Stresses

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For a long time, in plant cells as in animal cells, the nucleus was only considered as the organelle in which fundamental mechanisms such as replication and transcription occurred. While strong efforts were deployed in order to identify important families of transcription factors such as MYB, WRKY or TGA families (Dubos et al., 2010; Rushton et al., 2010), a few attention was devoted to our lack of knowledge about their regulation in regard to the physiological conditions of the plant cells. Whereas the major importance of posttranslational modification of proteins is well established for several decades regarding cytosolic proteins, the last years have been characterized by the discovery that the plant cell nucleus also contains all the enzymes necessary to assume these fundamental reactions in terms of signal transduction. For example, Mitogen-Activated Protein Kinases (MAPK) are well known protein kinases (PKs) involved in response to both biotic and abiotic stresses (for review see Dahan et al., 2009). These MAPKs play a crucial role in the regulation of specific gene expression by phosphorylating particular transcription factors. However, while they are well described in the cytosol, only recently researchers focused on their presence and involvement in the nucleus of plant cells challenged by abiotic stresses (for example, Ahlfors et al., 2004). Unfortunately, these authors like the other ones involved in plant cell nucleus studies did not try to identify the targets of these MAPK. This example highlights the fact that our knowledge of the incidence of protein posttranslational modifications regarding the cellular activities is still poorly rudimental, and particularly in the field of abiotic stress responses. Amongst the targets of these post-translational modifications, histones will be a piece of choice, being one of the favourite substrates for acetylation or methylation for example. Histones are small basic protein associated with DNA to form the chromatin. Chromatin