The molecular and cellular characterisation of plastid division proteins in arabidopsis

In plants an integral part of chloroplast development is division, as they are not created de novo but arise by binary fission from pre-existing plastids in the cytosol. Because of plastids prokaryotic origin bacterial cell division has been successfully used as a paradigm for plastid division. This has resulted in the identification of the key plastid division components Ftsz, MinD and MinE. Recent efforts in the cloning of the disrupted loci in several of the accumulation and replication of chloroplasts mutants has further revealed that the division of plastids is controlled by a combination of prokaryote-derived and host eukaryote-derived proteins residing not only in the plastid stroma but also in the cytoplasm. Despite the recent characterisation of several new plastid division components very little is known about how these components function to bring about the event of chloroplast division. This study aims to increase our understanding of the chloroplast division processes through the identification of new components and the detailed functional analysis of known stromal chloroplast division components. The identification of GIANT CHLOROPLAST 1 (GC1), a new nuclear-encoded protein essential for correct plastid division in Arabidopsis, is described, in addition to the use of yeast-two hybrids screens to identify novel plastid division components. Furthermore potential protein-protein interactions between all known stromal plastid division proteins are analysed using a combination of techniques and an intraplastidic protein-protein interaction map of plastid division proteins in Arabidopsis is presented. Based on data derived from this Map one stromal plastid division component, AtMinE1, is analysed in further detail to begin to dissect the mechanism by which the Min proteins function in Arabidopsis to mediate the correct placement of the division site.