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Micrasterias as a Model System in Plant Cell Biology.

Lütz-Meindl U - Front Plant Sci (2016)

Bottom Line: The review focuses particularly on cell wall formation and composition, dictyosomal structure and function, cytoskeleton control of growth and morphogenesis as well as on ionic regulation and signal transduction.It has been also shown in the recent years that Micrasterias is a highly sensitive indicator for environmental stress impact such as heavy metals, high salinity, oxidative stress or starvation.This review is intended to summarize and discuss the most important results obtained in Micrasterias in the last 20 years and to compare the results to similar processes in higher plant cells.

View Article: PubMed Central - PubMed

Affiliation: Plant Physiology Division, Cell Biology Department, University of Salzburg Salzburg, Austria.

ABSTRACT
The unicellular freshwater alga Micrasterias denticulata is an exceptional organism due to its complex star-shaped, highly symmetric morphology and has thus attracted the interest of researchers for many decades. As a member of the Streptophyta, Micrasterias is not only genetically closely related to higher land plants but shares common features with them in many physiological and cell biological aspects. These facts, together with its considerable cell size of about 200 μm, its modest cultivation conditions and the uncomplicated accessibility particularly to any microscopic techniques, make Micrasterias a very well suited cell biological plant model system. The review focuses particularly on cell wall formation and composition, dictyosomal structure and function, cytoskeleton control of growth and morphogenesis as well as on ionic regulation and signal transduction. It has been also shown in the recent years that Micrasterias is a highly sensitive indicator for environmental stress impact such as heavy metals, high salinity, oxidative stress or starvation. Stress induced organelle degradation, autophagy, adaption and detoxification mechanisms have moved in the center of interest and have been investigated with modern microscopic techniques such as 3-D- and analytical electron microscopy as well as with biochemical, physiological and molecular approaches. This review is intended to summarize and discuss the most important results obtained in Micrasterias in the last 20 years and to compare the results to similar processes in higher plant cells.

No MeSH data available.


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Transmission electron microscopy micrographs of mitochondria (A), FIB-SEM image of degrading dictyosome (B) and 3-D reconstruction of degrading dictyosome from FIB-SEM series (C) after exposure of Micrasterias to KCl. (A) Mitochondria with balloon-like protrusions of outer membrane and condensed matrix. (B) The colored asterisks indicate parts of the dictyosome that are reconstructed in (C). (C) The reconstruction shows that the dictyosomal cisternae form balls during degradation. Remnants of dictyosomal cisternae in red, ER in blue, small vesicles represent degradation products of cisternae. Scale bars are 1 μm. (B,C) Reprinted with permission from Lütz-Meindl et al. (2015), Copyright© 2015 Royal Microscopical Society.
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Figure 7: Transmission electron microscopy micrographs of mitochondria (A), FIB-SEM image of degrading dictyosome (B) and 3-D reconstruction of degrading dictyosome from FIB-SEM series (C) after exposure of Micrasterias to KCl. (A) Mitochondria with balloon-like protrusions of outer membrane and condensed matrix. (B) The colored asterisks indicate parts of the dictyosome that are reconstructed in (C). (C) The reconstruction shows that the dictyosomal cisternae form balls during degradation. Remnants of dictyosomal cisternae in red, ER in blue, small vesicles represent degradation products of cisternae. Scale bars are 1 μm. (B,C) Reprinted with permission from Lütz-Meindl et al. (2015), Copyright© 2015 Royal Microscopical Society.

Mentions: Experimental addition of KCl or NaCl to the culture medium leads to severe ultrastructural and physiological changes in M. denticulata that can be clearly distinguished from changes induced by osmotic stress (Affenzeller et al., 2009a,b). KCl (200 mM) caused the most pronounced effects by inducing foam-like vacuolization of the cytoplasm and severe morphological changes of mitochondria even after 3 h incubation. The outer membrane of all mitochondria showed balloon-like protrusions and their matrix appeared condensed indicating a kind of shrinkage induced by KCl induced intra-organelle osmotic changes (Figure 7A). Similar structural alterations of mitochondria are known from higher plant cells under anoxic conditions (Virolainen et al., 2002) and also from nerve cell during PCD (Muriel et al., 2000). Interestingly the severe structural changes did not influence their function in Micrasterias. Respiration in KCl exposed cells was not decreased (Affenzeller et al., 2009b).


Micrasterias as a Model System in Plant Cell Biology.

Lütz-Meindl U - Front Plant Sci (2016)

Transmission electron microscopy micrographs of mitochondria (A), FIB-SEM image of degrading dictyosome (B) and 3-D reconstruction of degrading dictyosome from FIB-SEM series (C) after exposure of Micrasterias to KCl. (A) Mitochondria with balloon-like protrusions of outer membrane and condensed matrix. (B) The colored asterisks indicate parts of the dictyosome that are reconstructed in (C). (C) The reconstruction shows that the dictyosomal cisternae form balls during degradation. Remnants of dictyosomal cisternae in red, ER in blue, small vesicles represent degradation products of cisternae. Scale bars are 1 μm. (B,C) Reprinted with permission from Lütz-Meindl et al. (2015), Copyright© 2015 Royal Microscopical Society.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4940373&req=5

Figure 7: Transmission electron microscopy micrographs of mitochondria (A), FIB-SEM image of degrading dictyosome (B) and 3-D reconstruction of degrading dictyosome from FIB-SEM series (C) after exposure of Micrasterias to KCl. (A) Mitochondria with balloon-like protrusions of outer membrane and condensed matrix. (B) The colored asterisks indicate parts of the dictyosome that are reconstructed in (C). (C) The reconstruction shows that the dictyosomal cisternae form balls during degradation. Remnants of dictyosomal cisternae in red, ER in blue, small vesicles represent degradation products of cisternae. Scale bars are 1 μm. (B,C) Reprinted with permission from Lütz-Meindl et al. (2015), Copyright© 2015 Royal Microscopical Society.
Mentions: Experimental addition of KCl or NaCl to the culture medium leads to severe ultrastructural and physiological changes in M. denticulata that can be clearly distinguished from changes induced by osmotic stress (Affenzeller et al., 2009a,b). KCl (200 mM) caused the most pronounced effects by inducing foam-like vacuolization of the cytoplasm and severe morphological changes of mitochondria even after 3 h incubation. The outer membrane of all mitochondria showed balloon-like protrusions and their matrix appeared condensed indicating a kind of shrinkage induced by KCl induced intra-organelle osmotic changes (Figure 7A). Similar structural alterations of mitochondria are known from higher plant cells under anoxic conditions (Virolainen et al., 2002) and also from nerve cell during PCD (Muriel et al., 2000). Interestingly the severe structural changes did not influence their function in Micrasterias. Respiration in KCl exposed cells was not decreased (Affenzeller et al., 2009b).

Bottom Line: The review focuses particularly on cell wall formation and composition, dictyosomal structure and function, cytoskeleton control of growth and morphogenesis as well as on ionic regulation and signal transduction.It has been also shown in the recent years that Micrasterias is a highly sensitive indicator for environmental stress impact such as heavy metals, high salinity, oxidative stress or starvation.This review is intended to summarize and discuss the most important results obtained in Micrasterias in the last 20 years and to compare the results to similar processes in higher plant cells.

View Article: PubMed Central - PubMed

Affiliation: Plant Physiology Division, Cell Biology Department, University of Salzburg Salzburg, Austria.

ABSTRACT
The unicellular freshwater alga Micrasterias denticulata is an exceptional organism due to its complex star-shaped, highly symmetric morphology and has thus attracted the interest of researchers for many decades. As a member of the Streptophyta, Micrasterias is not only genetically closely related to higher land plants but shares common features with them in many physiological and cell biological aspects. These facts, together with its considerable cell size of about 200 μm, its modest cultivation conditions and the uncomplicated accessibility particularly to any microscopic techniques, make Micrasterias a very well suited cell biological plant model system. The review focuses particularly on cell wall formation and composition, dictyosomal structure and function, cytoskeleton control of growth and morphogenesis as well as on ionic regulation and signal transduction. It has been also shown in the recent years that Micrasterias is a highly sensitive indicator for environmental stress impact such as heavy metals, high salinity, oxidative stress or starvation. Stress induced organelle degradation, autophagy, adaption and detoxification mechanisms have moved in the center of interest and have been investigated with modern microscopic techniques such as 3-D- and analytical electron microscopy as well as with biochemical, physiological and molecular approaches. This review is intended to summarize and discuss the most important results obtained in Micrasterias in the last 20 years and to compare the results to similar processes in higher plant cells.

No MeSH data available.


Related in: MedlinePlus