Ultrastructural features of the constricted region of dividing plastids

Oross, J. W.; Possingham, J. V.

doi:10.1007/bf01403669

Cited by 55 publications

(31 citation statements)

References 11 publications

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“…9B). This is the first description of a constriction ring in the anthocerotes, although similar rings have been observed in chloroplast division in many plants (Oross & Possingham, 1989;Tewinkel & Volkman, 1987;Kuroiw a, 1989). It is assumed that all of these constriction rings are actin.…”

Section: Chloroplast Divisionsupporting

confidence: 67%

The anthocerote chloroplast: a review

Vaughn

Ligrone²,

Owen

et al. 1992

New Phytologist

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SUMMARY This review covers previous data, together with new information from our laboratories, on the subject of the anthocerote chloroplast. Unlike all other archegoniates, most species of anthocerote have pyrenoids in their chloroplasts. The pyrenoid is the site of accumulation of the first enzyme in the C3 photosynthetic cycle, ribulose bispbosphate carboxylase/oxygenase. Unlike most algae, the hornwort pyrenoid is composed of distinct subunits, numbering up to several hundred. Pyrenoid morphology is quite variable among the genera in shape, fine structure, and distribution of inclusions. Another unique feature of the anthocerote chloroplast is the presence of thylakoids that connect adjacent granal stacks at right angles to the long axis of the granum (so‐called channel thylakoids), resulting in a 'spongy’arrangement of the thylakoid system. The granal stacks of anthocerotes are like the‘pseudograna’of green algae because they lack the highly‐curved end membranes typical of all other embryophytes. The channel thylakoids are enriched in photosystem (PS) I and the grana are enriched in PS II. The chloroplast envelope is a double membrane structure with regions of appression, much like that of other green plants. The apieal cell of the gametophyte contains chloroplasts similar to the mature chloroplasts of the thallus, although certain gametophytic tissues may contain underdeveloped plastids. Chloroplasts in cells around Nostoc colonies and in cells invaded by mycorrhizal fungi have thylakoids mainly in pairs, and small or absent pyrenoids. A number of similarly reduced plastids are noted in the placental cells at the sporophyte/gametophyte junction and in developing spores. The greatest reduction is observed in spermatid cell plastids, which at maturity consist of only a small starch grain surrounded by the envelope. Chromoplast‐like organelles are found in the cells of the antheridial jacket in some genera; these contain numerous osmiophilic globules that are probably pigment aggregations. Colourless bead‐like plastids occur in the rhizoids; these seem to develop by fragmentation of the single chloroplast in the rhizoid initials, concomitant with the loss of chlorophyll. Chloroplast division is a tightly controlled process and, in uniplastidic species, always occurs just before nuclear division, with the participation of a unique system of chloroplast‐associated microtubules. The number of chloroplasts per cell is quite variable in some genera, although most species have but a single chloroplast in each cell of the gametophyte. Chloroplast shape is also variable from ellipsoidal, dumbbell‐shaped, to irregular. These data indicate that the anthocerote chloroplast is unique among the embryophytes and are in line with the notion of an isolated position in the plant kingdom. Certain features of chloroplast morphology appear to be typical of certain genera and might prove useful in taxonomic decisions at the generic level.

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Section: Chloroplast Divisionsupporting

confidence: 67%

The anthocerote chloroplast: a review

Vaughn

Ligrone²,

Owen

et al. 1992

New Phytologist

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“…This electrondense ring, which is often called the plastid-dividing ring (PD), becomes visible by electron microscopy only in the latter stages of the process. Nevertheless, PDs have been observed in dividing chloroplasts and proplastids from several different species ( Figure 1H; Susuki and Ueda, 1975;Leech et al, 1981;Oross and Possingham, 1989;Robertson et al, 1996). Moreover, in some cases PDs appear to form a torus, with one component on the inside of the plastid and one component on the outside (Hashimoto, 1986).…”

Section: Cell Biology Of Plastid Division Cell Biology Of Plastid DIVmentioning

confidence: 99%

“…The process of plastid division has been characterized morphologically from careful analysis of light and electron microscopy images (Leech et al, 1981;Oross and Possingham, 1989;Robertson et al, 1996). It is initiated by a constriction in the middle of the plastid, which narrows further and, in the later stages of division, can form a thin isthmus that joins the two daughter plastids ( Figures 1A to 1E).…”

Section: Cell Biology Of Plastid Division Cell Biology Of Plastid DIVmentioning

confidence: 99%

Plastid Division and Development

Pyke

1999

Plant Cell

226

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“…The electron-dense material often can be resolved into two concentric rings, one on the stromal face of the inner envelope and one on the cytosolic face of the outer envelope (Hashimoto, 1986;Oross and Possingham, 1989;Duckett and Ligrone, 1993;Kuroiwa et al, 1998). Little else is known regarding the structure of the division apparatus.…”

Section: Introductionmentioning

confidence: 99%

Chloroplast Division in Higher Plants Requires Members of Two Functionally Divergent Gene Families with Homology to Bacterial ftsZ

et al. 1998

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The division of plastids is critical for viability in photosynthetic eukaryotes, but the mechanisms associated with this process are still poorly understood. We previously identified a nuclear gene from Arabidopsis encoding a chloroplastlocalized homolog of the bacterial cell division protein FtsZ, an essential cytoskeletal component of the prokaryotic cell division apparatus. Here, we report the identification of a second nuclear-encoded FtsZ-type protein from Arabidopsis that does not contain a chloroplast targeting sequence or other obvious sorting signals and is not imported into isolated chloroplasts, which strongly suggests that it is localized in the cytosol. We further demonstrate using antisense technology that inhibiting expression of either Arabidopsis FtsZ gene ( AtFtsZ1-1 or AtFtsZ2-1 ) in transgenic plants reduces the number of chloroplasts in mature leaf cells from 100 to one, indicating that both genes are essential for division of higher plant chloroplasts but that each plays a distinct role in the process. Analysis of currently available plant FtsZ sequences further suggests that two functionally divergent FtsZ gene families encoding differentially localized products participate in chloroplast division. Our results provide evidence that both chloroplastic and cytosolic forms of FtsZ are involved in chloroplast division in higher plants and imply that important differences exist between chloroplasts and prokaryotes with regard to the roles played by FtsZ proteins in the division process. INTRODUCTIONA number of metabolic pathways crucial for plant growth and development are housed in plastids. Among the various types of plastids present in plants, chloroplasts have been studied most extensively because of their role in photosynthesis. However, plastids also synthesize various amino acids, lipids, and plant growth regulators and so are assumed to be essential for viability of all plant cells (Mullet, 1988). For plastid continuity to be maintained during cell division and for photosynthetic tissues to accumulate the high numbers of chloroplasts required for maximum photosynthetic productivity, plastids must divide. Most of the available information concerning the process of plastid division is based on morphological and ultrastructural observations of dividing chloroplasts. During division, chloroplasts exhibit a dumbbell-shaped appearance in which the division furrow becomes progressively narrower. It is therefore generally agreed that chloroplast division occurs by a binary fission mechanism involving constriction of the envelope membranes (Leech, 1976;Possingham et al., 1988;Whatley, 1988).In plastids from a variety of higher plant and algal species, an electron-dense "plastid dividing ring" of unknown composition has been described in association with the zone of constriction. The electron-dense material often can be resolved into two concentric rings, one on the stromal face of the inner envelope and one on the cytosolic face of the outer envelope (Hashimoto, 1986;Oross and Possingham, 1989;D...

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Ultrastructural features of the constricted region of dividing plastids

Cited by 55 publications

References 11 publications

The anthocerote chloroplast: a review

The anthocerote chloroplast: a review

Plastid Division and Development

Chloroplast Division in Higher Plants Requires Members of Two Functionally Divergent Gene Families with Homology to Bacterial ftsZ

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