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Jodi Maple

Publications and source records attributed to Jodi Maple.

6 recordsLinked to original sources
PubMed2006

Plastid division: evolution, mechanism and complexity.

BACKGROUND: The continuity of chloroplasts is maintained by division of pre-existing chloroplasts. Chloroplasts originated as bacterial endosymbionts; however, the majority of bacterial division factors are absent from chloroplasts and the eukaryotic host has added several new components. For example, the ftsZ gene has been duplicated and modified, and the Min system has retained MinE and MinD but lost MinC, acquiring at least one new component ARC3. Further, the mechanism has evolved to include two members of the dynamin protein family, ARC5 and FZL, and plastid-dividing (PD) rings were most probably added by the eukaryotic host. SCOPE: Deciphering how the division of plastids is coordinated and controlled by nuclear-encoded factors is key to our understanding of this important biological process. Through a number of molecular-genetic and biochemical approaches, it is evident that FtsZ initiates plastid division where the coordinated action of MinD and MinE ensures correct FtsZ (Z)-ring placement. Although the classical FtsZ antagonist MinC does not exist in plants, ARC3 may fulfil this role. Together with other prokaryotic-derived proteins such as ARC6 and GC1 and key eukaryotic-derived proteins such as ARC5 and FZL, these proteins make up a sophisticated division machinery. The regulation of plastid division in a cellular context is largely unknown; however, recent microarray data shed light on this. Here the current understanding of the mechanism of chloroplast division in higher plants is reviewed with an emphasis on how recent findings are beginning to shape our understanding of the function and evolution of the components. CONCLUSIONS: Extrapolation from the mechanism of bacterial cell division provides valuable clues as to how the chloroplast division process is achieved in plant cells. However, it is becoming increasingly clear that the highly regulated mechanism of plastid division within the host cell has led to the evolution of features unique to the plastid division process.

Arabidopsis Proteins↗
PubMed2005

The molecular biology of plastid division in higher plants.

Plastids are essential plant organelles vital for life on earth, responsible not only for photosynthesis but for many fundamental intermediary metabolic reactions. Plastids are not formed de novo but arise by binary fission from pre-existing plastids, and plastid division therefore represents an important process for the maintenance of appropriate plastid populations in plant cells. Plastid division comprises an elaborate pathway of co-ordinated events which include division machinery assembly at the division site, the constriction of envelope membranes, membrane fusion and, ultimately, the separation of the two new organelles. Because of their 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, as well as novel proteins with similarities to prokaryotic cell division proteins. Through a combination of approaches involving molecular genetics, cell biology, and biochemistry, it is now becoming clear that these proteins act in concert during plastid division, exhibiting both similarities and differences compared with their bacterial counterparts. 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. Based on the available data to date, a working model is presented showing the protein components involved in plastid division, their subcellular localization, and their protein interaction properties.

Cell Division↗
PubMed2005

Plastid division is mediated by combinatorial assembly of plastid division proteins.

Plastids arise by division from pre-existing organelles, and with the recent characterization of several new components of plastid division our understanding of the division process in higher plants has improved dramatically. However, it is still not known how these different protein components act together during division. Here we analyse protein-protein interactions between all known stromal plastid division proteins. Using a combination of quantitative yeast two-hybrid assays, in planta co-localization studies, fluorescence resonance energy transfer and bimolecular fluorescence complementation assays we show that these proteins do not act in isolation but rather in protein complexes to govern appropriate plastid division. We have previously shown that AtMinD1 forms functional homodimers and we show here that in addition to homodimerization AtMinD1 also interacts with AtMinE1. Furthermore, AtMinE1 has the ability to homodimerize. We also demonstrate that proteins from both FtsZ families (AtFtsZ1-1 and AtFtsZ2-1) not only interact with themselves but also with each other, and we show that these interactions are not dependent on correct Z-ring formation. Further to this we demonstrate that ARC6 specifically interacts with the core domain of AtFtsZ2-1, but not with AtFtsZ1-1, providing in planta evidence for a functional difference between the two FtsZ protein families in plants. Our studies have enabled us to construct a meaningful intraplastidic protein-protein interaction map of all known stromal plastid division proteins in Arabidopsis.

Arabidopsis Proteins↗
PubMed2004

GIANT CHLOROPLAST 1 is essential for correct plastid division in Arabidopsis.

Plastids are vital plant organelles involved in many essential biological processes. Plastids are not created de novo but divide by binary fission mediated by nuclear-encoded proteins of both prokaryotic and eukaryotic origin. Although several plastid division proteins have been identified in plants, limited information exists regarding possible division control mechanisms. Here, we describe the identification of GIANT CHLOROPLAST 1 (GC1), a new nuclear-encoded protein essential for correct plastid division in Arabidopsis. GC1 is plastid-localized and is anchored to the stromal surface of the chloroplast inner envelope by a C-terminal amphipathic helix. In Arabidopsis, GC1 deficiency results in mesophyll cells harbouring one to two giant chloroplasts, whilst GC1 overexpression has no effect on division. GC1 can form homodimers but does not show any interaction with the Arabidopsis plastid division proteins AtFtsZ1-1, AtFtsZ2-1, AtMinD1, or AtMinE1. Analysis reveals that GC1-deficient giant chloroplasts contain densely packed wild-type-like thylakoid membranes and that GC1-deficient leaves exhibit lower rates of CO(2) assimilation compared to wild-type. Although GC1 shows similarity to a putative cyanobacterial SulA cell division inhibitor, our findings suggest that GC1 does not act as a plastid division inhibitor but, rather, as a positive factor at an early stage of the division process.

Amino Acid Sequence↗
PubMed2002

The topological specificity factor AtMinE1 is essential for correct plastid division site placement in Arabidopsis.

In plant cells, plastids divide by binary fission involving a complex pathway of events. Although there are clear similarities between bacterial and plastid division, limited information exists regarding the mechanism of plastid division in higher plants. Here we demonstrate that AtMinE1, an Arabidopsis homologue of the bacterial MinE topological specificity factor, is an essential integral component of the plastid division machinery. In prokaryotes MinE imparts topological specificity during cell division by blocking division apparatus assembly at sites other than midcell. We demonstrate that overexpression of AtMinE1 in E. coli results in loss of topological specificity and minicell formation suggesting evolutionary conservation of MinE mode of action. We further show that AtMinE1 can indeed act as a topological specificity factor during plastid division revealing that AtMinE1 overexpression in Arabidopsis seedlings results in division site misplacement giving rise to multiple constrictions along the length of plastids. In agreement with cell division studies in bacteria, AtMinE1 and AtMinD1 show distinct intraplastidic localisation patterns suggestive of dynamic localisation behaviour. Taken together our findings demonstrate that AtMinE1 is an evolutionary conserved topological specificity factor, most probably acting in concert with AtMinD1, required for correct plastid division in Arabidopsis.

Arabidopsis↗