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Skeletons in the closet. How do chloroplasts stay in shape?

McFadden GI - J. Cell Biol. (2000)

View Article: PubMed Central - PubMed

Affiliation: Plant Cell Biology Research Centre, School of Botany, University of Melbourne, Parkville 3010, Australia.

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FtsZ tubules, which may be higher order versions of the sheets and rings (Lu et al. 2000), bear superficial resemblance to cytosolic microtubules of eukaryotes... Tubules are not routinely visualized in bacteria (Bermudes et al. 1994), which made it difficult to assess the physiological importance of the in vitro assembled FtsZ tubules (Lu et al. 2000)... This model for chloroplast tubules bears an extraordinary resemblance to the models for in vitro polymerized bacterial FtsZ tubules (Trusca et al. 1998; Lu et al. 2000)... FtsZ tubules have an outer diameter of 23 nm, a wall thickness of 5.4 nm, and comprise a twin helix with a pitch of either 18° or 24°, depending on whether the tubes are four or five start helices (Lu et al. 2000)... At this time, eukaryotic cytosolic microtubules were only beginning to be characterized, and Hoffman 1967 and Pickett-Heaps 1968 related the chloroplast tubules to cytoplasmic microtubules, although at the same time they recognized key differences in the substructure of the two types of tubules... Kiessling et al. 2000 also observed possible plastid division rings at the constriction between two nascent daughter chloroplasts, and these could be plastid division rings or chloroplast Z rings... Interestingly, plants have multiple chloroplast FtsZ genes, so the protein may have multiple functions in chloroplasts and plastids, perhaps being responsible not only for division, but also for maintenance of plastid shape, just as tubulin has roles in mitosis and cell shape in the eukaryotic cytoplasm... Kiessling et al. 2000 propose that the plastoskeleton evolved to compensate for the loss of the peptidoglycan wall during integration of the cyanobacterial endosymbiont... This hypothesis predicts that plastids of the alga Cyanophora, which retain a peptidoglycan wall, will lack a plastoskeleton... It will also be interesting to learn whether FtsZ tubules have skeletal roles in wall-less bacteria, or even mitochondria... FtsZ was recently implicated as having a role in mitochondrial division of certain algae (Beech and Gilson 2000; Beech et al. 2000), but dynamins appear to have taken over the division function in animal and yeast mitochondria (Erickson 2000)... There is no evidence of cytoskeletal structures within mitochondria as yet, so how is their shape maintained?

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Confocal image of Physcomitrella patens protoplast expressing PpFtsZ1/GFP fusion protein. GFP fluorescence forms a reticulated fibrillar network (a plastoskeleton) within the plastid (left). Red autofluorescence defines the individual chloroplasts (right). Micrograph courtesy of Justine Kiessling.
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Figure 1: Confocal image of Physcomitrella patens protoplast expressing PpFtsZ1/GFP fusion protein. GFP fluorescence forms a reticulated fibrillar network (a plastoskeleton) within the plastid (left). Red autofluorescence defines the individual chloroplasts (right). Micrograph courtesy of Justine Kiessling.

Mentions: Breakthroughs in microscopy technology provide new insights into cell biology. Early microscopes allowed Robert Hooke to see cells. Improved staining techniques enabled Camillo Golgi to see the apparatus that bears his name, and Robert Feulgen to visualize DNA in chromosomes. Similarly, EM allowed Keith Porter to visualize the endomembrane system. More recently, transgenic technology using fluorescent reporter proteins has enabled us to visualize cryptic or ephemeral processes and structures in living cells. The latest revelation with this technology is in chloroplast biology. On page 945 of this issue, Kiessling et al. show that fusion of green fluorescent protein (GFP) with the FtsZ (filament temperature sensitive Z) protein targeted to chloroplasts of the moss Physcomitrella reveals a network of fibers within the chloroplast (Fig. 1). They dub this network the plastoskeleton, since it is reminiscent of cytoskeletons. Plant biologists have long wondered how chloroplasts (and their nongreen relatives, the plastids) maintain their specific shapes, which range from the more mundane ovoid versions of plants to the spectacular starbursts and spirals of the algae. Kiessling et al. 2000 now suggests that FtsZ could be the answer.


Skeletons in the closet. How do chloroplasts stay in shape?

McFadden GI - J. Cell Biol. (2000)

Confocal image of Physcomitrella patens protoplast expressing PpFtsZ1/GFP fusion protein. GFP fluorescence forms a reticulated fibrillar network (a plastoskeleton) within the plastid (left). Red autofluorescence defines the individual chloroplasts (right). Micrograph courtesy of Justine Kiessling.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2169437&req=5

Figure 1: Confocal image of Physcomitrella patens protoplast expressing PpFtsZ1/GFP fusion protein. GFP fluorescence forms a reticulated fibrillar network (a plastoskeleton) within the plastid (left). Red autofluorescence defines the individual chloroplasts (right). Micrograph courtesy of Justine Kiessling.
Mentions: Breakthroughs in microscopy technology provide new insights into cell biology. Early microscopes allowed Robert Hooke to see cells. Improved staining techniques enabled Camillo Golgi to see the apparatus that bears his name, and Robert Feulgen to visualize DNA in chromosomes. Similarly, EM allowed Keith Porter to visualize the endomembrane system. More recently, transgenic technology using fluorescent reporter proteins has enabled us to visualize cryptic or ephemeral processes and structures in living cells. The latest revelation with this technology is in chloroplast biology. On page 945 of this issue, Kiessling et al. show that fusion of green fluorescent protein (GFP) with the FtsZ (filament temperature sensitive Z) protein targeted to chloroplasts of the moss Physcomitrella reveals a network of fibers within the chloroplast (Fig. 1). They dub this network the plastoskeleton, since it is reminiscent of cytoskeletons. Plant biologists have long wondered how chloroplasts (and their nongreen relatives, the plastids) maintain their specific shapes, which range from the more mundane ovoid versions of plants to the spectacular starbursts and spirals of the algae. Kiessling et al. 2000 now suggests that FtsZ could be the answer.

View Article: PubMed Central - PubMed

Affiliation: Plant Cell Biology Research Centre, School of Botany, University of Melbourne, Parkville 3010, Australia.

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

FtsZ tubules, which may be higher order versions of the sheets and rings (Lu et al. 2000), bear superficial resemblance to cytosolic microtubules of eukaryotes... Tubules are not routinely visualized in bacteria (Bermudes et al. 1994), which made it difficult to assess the physiological importance of the in vitro assembled FtsZ tubules (Lu et al. 2000)... This model for chloroplast tubules bears an extraordinary resemblance to the models for in vitro polymerized bacterial FtsZ tubules (Trusca et al. 1998; Lu et al. 2000)... FtsZ tubules have an outer diameter of 23 nm, a wall thickness of 5.4 nm, and comprise a twin helix with a pitch of either 18° or 24°, depending on whether the tubes are four or five start helices (Lu et al. 2000)... At this time, eukaryotic cytosolic microtubules were only beginning to be characterized, and Hoffman 1967 and Pickett-Heaps 1968 related the chloroplast tubules to cytoplasmic microtubules, although at the same time they recognized key differences in the substructure of the two types of tubules... Kiessling et al. 2000 also observed possible plastid division rings at the constriction between two nascent daughter chloroplasts, and these could be plastid division rings or chloroplast Z rings... Interestingly, plants have multiple chloroplast FtsZ genes, so the protein may have multiple functions in chloroplasts and plastids, perhaps being responsible not only for division, but also for maintenance of plastid shape, just as tubulin has roles in mitosis and cell shape in the eukaryotic cytoplasm... Kiessling et al. 2000 propose that the plastoskeleton evolved to compensate for the loss of the peptidoglycan wall during integration of the cyanobacterial endosymbiont... This hypothesis predicts that plastids of the alga Cyanophora, which retain a peptidoglycan wall, will lack a plastoskeleton... It will also be interesting to learn whether FtsZ tubules have skeletal roles in wall-less bacteria, or even mitochondria... FtsZ was recently implicated as having a role in mitochondrial division of certain algae (Beech and Gilson 2000; Beech et al. 2000), but dynamins appear to have taken over the division function in animal and yeast mitochondria (Erickson 2000)... There is no evidence of cytoskeletal structures within mitochondria as yet, so how is their shape maintained?

Show MeSH