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The Arabidopsis minE mutation causes new plastid and FtsZ1 localization phenotypes in the leaf epidermis.

Fujiwara MT, Kojo KH, Kazama Y, Sasaki S, Abe T, Itoh RD - Front Plant Sci (2015)

Bottom Line: Plastids in the leaf epidermal cells of plants are regarded as immature chloroplasts that, like mesophyll chloroplasts, undergo binary fission.In atminE1, the size and shape of epidermal plastids varied widely, which contrasts with the plastid phenotype observed in atminE1 mesophyll cells.Observation of an atminE1 transgenic line harboring an AtMinE1 promoter::AtMinE1-yellow fluorescent protein fusion gene confirmed the expression and plastidic localization of AtMinE1 in the leaf epidermis.

View Article: PubMed Central - PubMed

Affiliation: RIKEN Nishina Center Saitama, Japan ; Graduate School of Science and Technology, Sophia University Tokyo, Japan.

ABSTRACT
Plastids in the leaf epidermal cells of plants are regarded as immature chloroplasts that, like mesophyll chloroplasts, undergo binary fission. While mesophyll chloroplasts have generally been used to study plastid division, recent studies have suggested the presence of tissue- or plastid type-dependent regulation of plastid division. Here, we report the detailed morphology of plastids and their stromules, and the intraplastidic localization of the chloroplast division-related protein AtFtsZ1-1, in the leaf epidermis of an Arabidopsis mutant that harbors a mutation in the chloroplast division site determinant gene AtMinE1. In atminE1, the size and shape of epidermal plastids varied widely, which contrasts with the plastid phenotype observed in atminE1 mesophyll cells. In particular, atminE1 epidermal plastids occasionally displayed grape-like morphology, a novel phenotype induced by a plastid division mutation. Observation of an atminE1 transgenic line harboring an AtMinE1 promoter::AtMinE1-yellow fluorescent protein fusion gene confirmed the expression and plastidic localization of AtMinE1 in the leaf epidermis. Further examination revealed that constriction of plastids and stromules mediated by the FtsZ1 ring contributed to the plastid pleomorphism in the atminE1 epidermis. These results illustrate that a single plastid division mutation can have dramatic consequences for epidermal plastid morphology, thereby implying that plastid division and morphogenesis are differentially regulated in epidermal and mesophyll plastids.

No MeSH data available.


Related in: MedlinePlus

Plastid morphology in leaf epidermis of atminE1. (A–J) Images of CFP-labeled plastids in leaf petiole epidermis of 2- or 3-week-old atminE1 seedlings. Fluorescence images of chlorophyll (colored in magenta) are also shown. Asterisks indicate plastid bodies with positive chlorophyll signals. Plastids in (D,F–I) lack signals. Bars = 10 μm (A–I) and 5 μm (J).
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Figure 2: Plastid morphology in leaf epidermis of atminE1. (A–J) Images of CFP-labeled plastids in leaf petiole epidermis of 2- or 3-week-old atminE1 seedlings. Fluorescence images of chlorophyll (colored in magenta) are also shown. Asterisks indicate plastid bodies with positive chlorophyll signals. Plastids in (D,F–I) lack signals. Bars = 10 μm (A–I) and 5 μm (J).

Mentions: Taking advantage of the merits of plastid-targeted CFP described above, we investigated the plastid morphology in leaf petiole epidermis of 2- and 3-week-old atminE1 seedlings using epifluorescence microscopy (Figure 2). While epidermal (pavement) cells of the leaf blade are puzzle piece-shaped with interdigitated lobes, those of the petiole assume a flat rectangular shape, making them more suitable for the observation of plastids and other organelles. First, we focused on the morphology of individual plastids. Even in the same cell, plastids were highly polymorphic in terms of their subplastidic structures such as main plastid bodies, stromules, and bulges. Importantly, it was often difficult to distinguish among these three structures (Figure 2A), which is often the case for non-green plastids (Schattat et al., 2015). Nonetheless, we typically observed giant plastids with long stromules (Figure 2B). As variations of this typical form, we observed shallow, wavy constrictions on stromules (Figure 2C) and seemingly fragmenting stromules (Figure 2D). These stromules often contained substructures resembling plastid bodies in their interior or terminal regions (Figures 2C,D). These characteristic morphologies of stromules were observed regardless of the presence of chlorophyll autofluorescence in their main plastid bodies. The atminE1 mutant also exhibited a unique morphological feature in the plastid bodies of the leaf epidermis. At low frequency, mini-sized plastid bodies aggregated into a grape-like clump (Figure 2E). In some cases, some of the plastid bodies within a clump emitted faint chlorophyll autofluorescence. Also, we noticed the presence of relatively immature, chlorophyll-free plastids, like those observed in the leaf epidermis of the A. thaliana arc6 mutant (Holzinger et al., 2008). This type of plastid assumed various shapes, appearing round, stretched, or with multiple constrictions (Figures 2F–I). We did not detect a significant relationship between plastid size and shape (Figures 2G,H), except for the predominance of a round form among small, poorly developed plastids. Another phenotype that is unique to the atminE1 epidermis among chloroplast division mutants examined thus far is the presence of mini-sized, chlorophyll-containing plastids (Figure 2J). Tiny plastids in the epidermis of chloroplast division mutants, which were previously reported, lacked chlorophyll (Holzinger et al., 2008).


The Arabidopsis minE mutation causes new plastid and FtsZ1 localization phenotypes in the leaf epidermis.

Fujiwara MT, Kojo KH, Kazama Y, Sasaki S, Abe T, Itoh RD - Front Plant Sci (2015)

Plastid morphology in leaf epidermis of atminE1. (A–J) Images of CFP-labeled plastids in leaf petiole epidermis of 2- or 3-week-old atminE1 seedlings. Fluorescence images of chlorophyll (colored in magenta) are also shown. Asterisks indicate plastid bodies with positive chlorophyll signals. Plastids in (D,F–I) lack signals. Bars = 10 μm (A–I) and 5 μm (J).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4593956&req=5

Figure 2: Plastid morphology in leaf epidermis of atminE1. (A–J) Images of CFP-labeled plastids in leaf petiole epidermis of 2- or 3-week-old atminE1 seedlings. Fluorescence images of chlorophyll (colored in magenta) are also shown. Asterisks indicate plastid bodies with positive chlorophyll signals. Plastids in (D,F–I) lack signals. Bars = 10 μm (A–I) and 5 μm (J).
Mentions: Taking advantage of the merits of plastid-targeted CFP described above, we investigated the plastid morphology in leaf petiole epidermis of 2- and 3-week-old atminE1 seedlings using epifluorescence microscopy (Figure 2). While epidermal (pavement) cells of the leaf blade are puzzle piece-shaped with interdigitated lobes, those of the petiole assume a flat rectangular shape, making them more suitable for the observation of plastids and other organelles. First, we focused on the morphology of individual plastids. Even in the same cell, plastids were highly polymorphic in terms of their subplastidic structures such as main plastid bodies, stromules, and bulges. Importantly, it was often difficult to distinguish among these three structures (Figure 2A), which is often the case for non-green plastids (Schattat et al., 2015). Nonetheless, we typically observed giant plastids with long stromules (Figure 2B). As variations of this typical form, we observed shallow, wavy constrictions on stromules (Figure 2C) and seemingly fragmenting stromules (Figure 2D). These stromules often contained substructures resembling plastid bodies in their interior or terminal regions (Figures 2C,D). These characteristic morphologies of stromules were observed regardless of the presence of chlorophyll autofluorescence in their main plastid bodies. The atminE1 mutant also exhibited a unique morphological feature in the plastid bodies of the leaf epidermis. At low frequency, mini-sized plastid bodies aggregated into a grape-like clump (Figure 2E). In some cases, some of the plastid bodies within a clump emitted faint chlorophyll autofluorescence. Also, we noticed the presence of relatively immature, chlorophyll-free plastids, like those observed in the leaf epidermis of the A. thaliana arc6 mutant (Holzinger et al., 2008). This type of plastid assumed various shapes, appearing round, stretched, or with multiple constrictions (Figures 2F–I). We did not detect a significant relationship between plastid size and shape (Figures 2G,H), except for the predominance of a round form among small, poorly developed plastids. Another phenotype that is unique to the atminE1 epidermis among chloroplast division mutants examined thus far is the presence of mini-sized, chlorophyll-containing plastids (Figure 2J). Tiny plastids in the epidermis of chloroplast division mutants, which were previously reported, lacked chlorophyll (Holzinger et al., 2008).

Bottom Line: Plastids in the leaf epidermal cells of plants are regarded as immature chloroplasts that, like mesophyll chloroplasts, undergo binary fission.In atminE1, the size and shape of epidermal plastids varied widely, which contrasts with the plastid phenotype observed in atminE1 mesophyll cells.Observation of an atminE1 transgenic line harboring an AtMinE1 promoter::AtMinE1-yellow fluorescent protein fusion gene confirmed the expression and plastidic localization of AtMinE1 in the leaf epidermis.

View Article: PubMed Central - PubMed

Affiliation: RIKEN Nishina Center Saitama, Japan ; Graduate School of Science and Technology, Sophia University Tokyo, Japan.

ABSTRACT
Plastids in the leaf epidermal cells of plants are regarded as immature chloroplasts that, like mesophyll chloroplasts, undergo binary fission. While mesophyll chloroplasts have generally been used to study plastid division, recent studies have suggested the presence of tissue- or plastid type-dependent regulation of plastid division. Here, we report the detailed morphology of plastids and their stromules, and the intraplastidic localization of the chloroplast division-related protein AtFtsZ1-1, in the leaf epidermis of an Arabidopsis mutant that harbors a mutation in the chloroplast division site determinant gene AtMinE1. In atminE1, the size and shape of epidermal plastids varied widely, which contrasts with the plastid phenotype observed in atminE1 mesophyll cells. In particular, atminE1 epidermal plastids occasionally displayed grape-like morphology, a novel phenotype induced by a plastid division mutation. Observation of an atminE1 transgenic line harboring an AtMinE1 promoter::AtMinE1-yellow fluorescent protein fusion gene confirmed the expression and plastidic localization of AtMinE1 in the leaf epidermis. Further examination revealed that constriction of plastids and stromules mediated by the FtsZ1 ring contributed to the plastid pleomorphism in the atminE1 epidermis. These results illustrate that a single plastid division mutation can have dramatic consequences for epidermal plastid morphology, thereby implying that plastid division and morphogenesis are differentially regulated in epidermal and mesophyll plastids.

No MeSH data available.


Related in: MedlinePlus