Thesis presented December 11, 2009
Abstract:
Plastids are a diverse group of organelles, comprising chloroplasts, found ubiquitously in plant cells and, like mitochondria, entered the eukaryotic lineage through endosymbiosis. Until recently, the most nucleus-encoded proteins required to chloroplasts functions are synthesized on 80S ribosomes in the cytosol as precursor with N-terminal cleavable targeting signal named “transit peptide” and imported into internal chloroplast compartments via TOC-TIC machinery located on the outer and inner membranes of chloroplast envelope [for new review see Jarvis, 2008]. However, news studies like the characterization in 2002 of a new protein located at the inner membrane of chloroplast envelope without N-terminal cleavable targeting signal [Miras
et al., 2002], the identification of an other protein prior targeted to endoplasmic reticulum and Golgi apparatus before chloroplast import in 2005 [Villarejo
et al., 2005] and the fact that some chloroplast proteins do not enter TOC-TIC machinery [Nada and Soll, 2004; Miras
et al., 2007] have revealed the existence of others pathways called alternative or noncanonical chloroplast import pathways [Jarvis, 2008]. In this context, my PhD project is to identify others proteins trafficking through alternative or noncanonical chloroplast import pathways in order to determine which mechanisms control these surprising imports. Two strategies of identification have been retained. One based on specific glycoprotein's isolation methods. Second strategy based on systematic proteomic approach of
Arabidopsis thaliana subplastidial fractions (envelope, stroma and thylakoids) followed by
in silico screening using bioinformatics tools.
Keywords:
Arabidopsis thaliana, secretory system, chloroplast, N-terminal targeting signal, glycosylation