A Comparison between Prolamellar Bodies and Prothylakoid Membranes of Etioplasts of Dark-Grown Wheat Concerning Lipid and Polypeptide Composition

Selstam, Eva; Sandelius, Anna Stina

doi:10.1104/pp.76.4.1036

Cited by 95 publications

(65 citation statements)

References 24 publications

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“…4 A and B), indicating that MGD1 is not important for plastid development in the dark. This result was somewhat unexpected because previous studies have shown that etioplast membranes contain high levels of MGD (29,30). One possible explanation is that the MGD synthase function of dark-grown Arabidopsis plants is fulfilled primarily by MGD2 and͞or MGD3, and not to any significant degree by MGD1.…”

Section: This Paper Describes the Identification And Characterizationcontrasting

confidence: 44%

Galactolipid deficiency and abnormal chloroplast development in the Arabidopsis MGD synthase 1 mutant

Jarvis

Dörmann

Peto

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

264

219

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The lipid monogalactosyl diacylglycerol (MGD) is a major structural component of photosynthetic membranes in chloroplasts. Its formation is catalyzed by the enzyme MGD synthase. In many plants, MGD derives from two different biosynthetic pathways: the prokaryotic pathway, which operates entirely within the plastid, and the eukaryotic pathway, which involves steps in the endoplasmic reticulum. Here, we describe the identification and characterization of an Arabidopsis mutant with a defective MGD synthase gene (MGD1). The mutant was identified in a screen of T-DNA lines for individuals with defects in chloroplast biogenesis. It has a yellowgreen phenotype that correlates with a Ϸ50% deficiency in total chlorophyll per plant. A single T-DNA insertion is located adjacent to the transcription initiation site of the MGD1 gene, and the abundance of MGD1 mRNA is reduced by 75% compared with wild type. Correlation between steady-state MGD1 transcript levels and MGD synthase activity (also reduced by 75% in mgd1) suggests that MGD1 is the most important MGD synthase in green tissues. The amount of MGD in mutant leaves is reduced by 42% compared with wild type. MGD from the mutant contains 23% less 16:3 fatty acid and 10% more 18:3 fatty acid. Because 16:3 is a characteristic feature of MGD from the prokaryotic pathway, it is possible that MGD1 operates with some preference in the prokaryotic pathway. Finally, the MGD-deficiency of mgd1 is correlated with striking defects in chloroplast ultrastructure, strongly suggesting a unique role for MGD in the structural organization of plastidic membranes.G alactose-containing lipids are the predominant nonproteinaceous components of photosynthetic membranes in plants, algae, and a variety of bacteria. The two most common galactolipids are monogalactosyl diacylglycerol (MGD) and digalactosyl diacylglycerol (DGD). In plants, MGD and DGD occur exclusively in plastidic membranes, where they account for about 50 and 20 mol% of the lipid matrix, respectively (1). Up to 80% of all lipids in plants are associated with photosynthetic membranes, and MGD is widely considered to be the most abundant membrane lipid on earth. Most vegetables and fruits in human and animal diets are rich in galactolipids, and their breakdown products represent an important dietary source of galactose and polyunsaturated fatty acids (2, 3).Galactolipids play an important role in the organization of photosynthetic membranes. The abundance and physical properties of MGD make it particularly important in this respect. Its small galactose head group and large unsaturated fatty acid chains give it a cone-like molecular shape and a consequent predisposition to form nonlamellar, hexagonal-phase aggregates (4). The molecular shape of MGD may be important for the structural organization of thylakoid membranes. Because much of the photosynthetic apparatus is embedded within thylakoids, the lipids that make up these membranes are of profound importance. Evidence also suggests that MGD is more directly involved in certain ph...

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Section: This Paper Describes the Identification And Characterizationcontrasting

confidence: 44%

Galactolipid deficiency and abnormal chloroplast development in the Arabidopsis MGD synthase 1 mutant

Jarvis

Dörmann

Peto

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

264

219

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“…In yellow wild-type seedlings, lutein and violaxanthin are associated with the PLB seen in Figure 8A (Selstam and Sandelius, 1984). However, in the orange-yellow ccr2 seedlings, various lycopene and carotene isomers accumulate (Figure 2A), the PLB is absent ( Figures 8D and 8E), and unlike any previously described PLB-deficient plants (Sundqvist and Dahlin, 1997), POR levels are unaffected and Pchlide levels are reduced only slightly (Figure 9) (Axelsson et al, 1982;Sundqvist and Dahlin, 1997).…”

Section: Carotenoids Plb Formation and Photomorphogenesismentioning

confidence: 78%

Identification of the Carotenoid Isomerase Provides Insight into Carotenoid Biosynthesis, Prolamellar Body Formation, and Photomorphogenesis

et al. 2002

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Carotenoids are essential photoprotective and antioxidant pigments synthesized by all photosynthetic organisms. Most carotenoid biosynthetic enzymes were thought to have evolved independently in bacteria and plants. For example, in bacteria, a single enzyme (CrtI) catalyzes the four desaturations leading from the colorless compound phytoene to the red compound lycopene, whereas plants require two desaturases (phytoene and -carotene desaturases) that are unrelated to the bacterial enzyme. We have demonstrated that carotenoid desaturation in plants requires a third distinct enzyme activity, the carotenoid isomerase (CRTISO), which, unlike phytoene and -carotene desaturases, apparently arose from a progenitor bacterial desaturase. The Arabidopsis CRTISO locus was identified by the partial inhibition of lutein synthesis in light-grown tissue and the accumulation of poly-cis -carotene precursors in dark-grown tissue of crtISO mutants. After positional cloning, enzymatic analysis of CRTISO expressed in Escherichia coli confirmed that the enzyme catalyzes the isomerization of poly-cis -carotenoids to all-trans -carotenoids. Etioplasts of darkgrown crtISO mutants accumulate acyclic poly-cis -carotenoids in place of cyclic all-trans -xanthophylls and also lack prolamellar bodies (PLBs), the lattice of tubular membranes that defines an etioplast. This demonstrates a requirement for carotenoid biosynthesis to form the PLB. The absence of PLBs in crtISO mutants demonstrates a function for this unique structure and carotenoids in facilitating chloroplast development during the first critical days of seedling germination and photomorphogenesis.

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“…The extremely fragile nature of an organelle which encloses starch granules causes a disruption of the envelope-membrane during isolation, thus precluding the isolation of the intact amyloplast while maintaining both its structural integrity and functional competence. Although the isolation of intact amyloplasts has been reported by several investigators using various plant materials (7,8,23,30), these reports appear to be still deficient; careful examination indicates that the evidence for the presence of an intact envelope surrounding the organelle appears to be rather weak.…”

mentioning

confidence: 93%

Isolation and Characterization of the Amyloplast Envelope-Membrane from Cultured White-Wild Cells of Sycamore (Acer pseudoplatanus L.)

Ngernprasirtsiri¹,

Harinasut²,

Macherel³

et al. 1988

Plant Physiol.

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To study the characteristic features of the amyloplast, a uniquely differentiated plastid-type which synthesizes and accumulates reserve starch, in comparison with those of the chloroplast, these two types of plastids were isolated from white-wild and green-mutant protoplasts of cultured sycamore (Acer pseudoplatanus L.) cells, respectively. The intactness of the isolated amyloplast preparations was 70%. Electron microscopic ultrastructural analysis of both plastid types revealed unique structural features of the green-mutant chloroplasts, including well developed grana membranes and abundant ribosomal particles and plastoglobuli. After osmotic rupture of the isolated amyloplasts and chloroplasts, a clear separation of the envelope-membranes was achieved by discontinuous sucrose density gradient centrifugation. Although the visible absorption spectra of the envelope lipid components were indistinguishable between the amyloplasts and chloroplasts, the envelope-membrane polypeptide patterns were clearly distinct as judged by denaturing electrophoresis. By immunoblotting analysis using the specific antiserum raised against the pea chloroplast 29-kilodalton Pi-translocator, the amount of this carrier-protein (31-kilodalton) in the white-wild amyloplast envelope-membranes was estimated to be at least 10-fold less than in the green-mutant envelopes.The amyloplast is a uniquely differentiated plastid-type which synthesizes and accumulates starch in the stromal matrix. It has long been hypothesized that this organelle is ontogenically and I

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A Comparison between Prolamellar Bodies and Prothylakoid Membranes of Etioplasts of Dark-Grown Wheat Concerning Lipid and Polypeptide Composition

Cited by 95 publications

References 24 publications

Galactolipid deficiency and abnormal chloroplast development in the Arabidopsis MGD synthase 1 mutant

Galactolipid deficiency and abnormal chloroplast development in the Arabidopsis MGD synthase 1 mutant

Identification of the Carotenoid Isomerase Provides Insight into Carotenoid Biosynthesis, Prolamellar Body Formation, and Photomorphogenesis

Isolation and Characterization of the Amyloplast Envelope-Membrane from Cultured White-Wild Cells of Sycamore (Acer pseudoplatanus L.)

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