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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.


Related in: MedlinePlus

Schematic drawing of stress-induced degradation of dictyosomes in Micrasterias. (A) Control dictyosome with 11 cisternae (cis-side in red). (B) Beginning degradation, outermost cis- and trans-cisternae form balls. (C) Proceeding degradation and reduction of cisternal number. Cisternal balls include other cisternal balls. Numerous degradation products are visible close to the degrading dictyosome. (D) Dictyosome has completely disintegrated into balls. (E) The cisternal balls fuse with long, stress-induced ER cisternae. Reprinted with permission from Lütz-Meindl et al. (2015), Copyright© 2015 Royal Microscopical Society.
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Figure 8: Schematic drawing of stress-induced degradation of dictyosomes in Micrasterias. (A) Control dictyosome with 11 cisternae (cis-side in red). (B) Beginning degradation, outermost cis- and trans-cisternae form balls. (C) Proceeding degradation and reduction of cisternal number. Cisternal balls include other cisternal balls. Numerous degradation products are visible close to the degrading dictyosome. (D) Dictyosome has completely disintegrated into balls. (E) The cisternal balls fuse with long, stress-induced ER cisternae. Reprinted with permission from Lütz-Meindl et al. (2015), Copyright© 2015 Royal Microscopical Society.

Mentions: In contrast, function of the endomembrane system was considerably impaired. ER cisternae were swollen and dramatically increased in number, whereas the cisternal number per Golgi stack decreased. Single dictyosomal cisternae were detached from the stack, both at the cis- and the trans-side. The remaining dictyosomal cisternae were completely inoperable as vesicles were no longer found in their proximity (Affenzeller et al., 2009b). When KCl treatment was continued for up to 24 h, degrading dictyosomes consisting of only two or three coiled cisternae were frequently found in contact with large ER compartments. 3-D analyses by FIB-SEM tomography provided evidence for the dictyosomal degradation process that occurred as consequence of KCl stress (Figure 8; Lütz-Meindl et al., 2015). Dictyosomal degradation starts with detachment of single cisternae from a stack. These cisternae form balls that may contain other cisternae of the same stack (Figures 7B,C). They increase in size by fusion with ER compartments and are finally absorbed by huge ER cisternae that pervade the cytoplasm. In contrast to our earlier assumptions (Affenzeller et al., 2009a,b) dictyosomes in Micrasterias are not disintegrated via autophagy. Although detailed studies on stress-induced dictyosomal disintegration are still missing there is also no evidence in the literature for autophagic degradation of dictyosomes in higher plant cells. Comprehensive articles that summarize selective autophagy in plants (Michaeli and Galili, 2014) report on autophagy of ER, mitochondria, plastids and peroxisomes, but not of dictyosomes.


Micrasterias as a Model System in Plant Cell Biology.

Lütz-Meindl U - Front Plant Sci (2016)

Schematic drawing of stress-induced degradation of dictyosomes in Micrasterias. (A) Control dictyosome with 11 cisternae (cis-side in red). (B) Beginning degradation, outermost cis- and trans-cisternae form balls. (C) Proceeding degradation and reduction of cisternal number. Cisternal balls include other cisternal balls. Numerous degradation products are visible close to the degrading dictyosome. (D) Dictyosome has completely disintegrated into balls. (E) The cisternal balls fuse with long, stress-induced ER cisternae. 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 8: Schematic drawing of stress-induced degradation of dictyosomes in Micrasterias. (A) Control dictyosome with 11 cisternae (cis-side in red). (B) Beginning degradation, outermost cis- and trans-cisternae form balls. (C) Proceeding degradation and reduction of cisternal number. Cisternal balls include other cisternal balls. Numerous degradation products are visible close to the degrading dictyosome. (D) Dictyosome has completely disintegrated into balls. (E) The cisternal balls fuse with long, stress-induced ER cisternae. Reprinted with permission from Lütz-Meindl et al. (2015), Copyright© 2015 Royal Microscopical Society.
Mentions: In contrast, function of the endomembrane system was considerably impaired. ER cisternae were swollen and dramatically increased in number, whereas the cisternal number per Golgi stack decreased. Single dictyosomal cisternae were detached from the stack, both at the cis- and the trans-side. The remaining dictyosomal cisternae were completely inoperable as vesicles were no longer found in their proximity (Affenzeller et al., 2009b). When KCl treatment was continued for up to 24 h, degrading dictyosomes consisting of only two or three coiled cisternae were frequently found in contact with large ER compartments. 3-D analyses by FIB-SEM tomography provided evidence for the dictyosomal degradation process that occurred as consequence of KCl stress (Figure 8; Lütz-Meindl et al., 2015). Dictyosomal degradation starts with detachment of single cisternae from a stack. These cisternae form balls that may contain other cisternae of the same stack (Figures 7B,C). They increase in size by fusion with ER compartments and are finally absorbed by huge ER cisternae that pervade the cytoplasm. In contrast to our earlier assumptions (Affenzeller et al., 2009a,b) dictyosomes in Micrasterias are not disintegrated via autophagy. Although detailed studies on stress-induced dictyosomal disintegration are still missing there is also no evidence in the literature for autophagic degradation of dictyosomes in higher plant cells. Comprehensive articles that summarize selective autophagy in plants (Michaeli and Galili, 2014) report on autophagy of ER, mitochondria, plastids and peroxisomes, but not of dictyosomes.

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