BIOSYNTHESIS IN ISOLATED <i>ACETABULARIA</i> CHLOROPLASTS

Shephard, David C.; Levin, Wendy B.

doi:10.1083/jcb.54.2.279

Cited by 23 publications

(5 citation statements)

References 25 publications

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“…Chlorophytes, the algae most often ingested by sacoglossans, produce numerous photosynthates including carbohydrates, lipids and proteins [3, 4, 10–13]. The main photosynthate produced however is starch, a combination of amylose and amylopectin [10].…”

Section: Introductionmentioning

confidence: 99%

“…The main photosynthate produced however is starch, a combination of amylose and amylopectin [10]. To establish whether or not photosynthates are made available to a sacoglossan slug, radiolabeling studies with 14 C or 13 C were conducted [5, 14–19], finding that both photosynthetically and heterotrophically fixed carbon is present in multiple slug-derived compounds for some species.…”

Section: Introductionmentioning

confidence: 99%

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Photosynthate accumulation in solar-powered sea slugs - starving slugs survive due to accumulated starch reserves

et al. 2017

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BackgroundSolar-powered sea slugs are famed for their ability to survive starvation due to incorporated algal chloroplasts. It is well established that algal-derived carbon can be traced in numerous slug-derived compounds, showing that slugs utilize the photosynthates produced by incorporated plastids. Recently, a new hypothesis suggests that the photosynthates produced are not continuously made available to the slug. Instead, at least some of the plastid’s photosynthetic products are stored in the plastid itself and only later become available to the slug. The long-term plastid-retaining slug, Elysia timida and its sole food source, Acetabularia acetabulum were examined to determine whether or not starch, a combination of amylose and amylopectin and the main photosynthate produced by A. acetabulum, is produced by the stolen plastids and whether it accumulates within individual kleptoplasts, providing an energy larder, made available to the slug at a later time.ResultsHistological sections of Elysia timida throughout a starvation period were stained with Lugol’s Iodine solution, a well-known stain for starch granules in plants. We present here for the first time, an increase in amylose concentration, within the slug’s digestive gland cells during a starvation period, followed by a sharp decrease. Chemically blocking photosynthesis in these tissues resulted in no observable starch, indicating that the starch in untreated animals is a product of photosynthetic activity.ConclusionThis suggests that kleptoplasts function as both, a nutritive producer and storage device, holding onto the polysaccharides they produce for a certain time until they are finally available and used by the starving slug to withstand extended starvation periods.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photosynthate accumulation in solar-powered sea slugs - starving slugs survive due to accumulated starch reserves

et al. 2017

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“…A filtration step with a 5-/Lm membrane has been used because it has been found to be effective in disrupting cytoplasts that are formed when Acetabularia cells are chopped (18). The extraction buffer has a high buffering capacity because vacuoles in the Acetabularia cells contribute a large amount of acid to the medium.…”

Section: Materials and Methods Preparation Of Chloroplasts A Meditementioning

confidence: 99%

Tandemly repeated nonribosomal DNA sequences in the chloroplast genome of an Acetabularia mediterranea strain.

Tymms¹,

Schweiger²

1985

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

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A purified chloroplast fraction was prepared from caps of the giant unicellular green alga Acetabularia mediterranea (strain 17). High molecular weight DNA obtained from these chloroplasts contains at least five copies of a 10-kilobase-pair (kbp) sequence tandemly arranged. This unique sequence is present in DNA from chloroplasts of all stages of the life cycle examined. A chloroplast rDNA clone from mustard hybridized with some restriction fragments from Acetabularia chloroplast DNA but not with the repeated sequence. An 8-kbp EcoRI-.Pst I fragment of the repeated sequence was cloned into pBR322 and used as a hybridization probe. No homology was found between the cloned 8-kbp sequence and chloroplast DNA from related species Acetabularia crenulata or chloroplast DNA from spinach.Chloroplast genomes are usually considered to have a conservative structure and to be circular with a contour length of 37-46 ,um in higher plants. A One of the most ancient families of green algae, Dacycladaceae, which is known by numerous fossil species, has a number of present day representatives of which Acetabularia is the best known. Early studies with Acetabularia have shown that DNA from chloroplast fractions contains long lengths of DNA when viewed in the electron microscope (7). The kinetic complexity of this DNA resembles that of Escherichia coli rather than that of Chlamydomonas (8). With this information we have started a study to further characterize the chloroplast genome of Acetabularia.In this paper we describe experiments that reveal that the chloroplast genome in a strain of Acetabularia mediterranea contains tandemly repeated sequences that are stable during the life cycle and that are not homologous to heterologous probes for ribosomal RNA genes. MATERIALS AND METHODS Preparation of Chloroplasts. A. mediterranea was grown inMuller's medium as described (for references, see ref. 9). Cells of three different stages, 1 cm long, 3.5 cm long (i.e., just prior to cap formation), and fully developed caps (9) were studied.Caps from A. mediterranea cells were harvested prior to the formation of secondary nuclei. Five-thousand caps ('100 g) were homogenized in a blender fitted with razor blades on a vertical shaft in 1 liter of ice-cold buffer A containing 0.6 M sorbitol, 0.1 M 2-{[tris (hydroxymethyl) methyl]amino}ethanesulfonic acid (Tes; pH 7.8), 0.005 M disodium EDTA, and 0.002 M 2,3-dihydroxy-1,4-dithiobutane.After five 3-sec bursts in the blender, the homogenate was filtered through two layers of Miracloth (Calbiochem) and 1 layer of 10-gm nylon cloth. Chloroplasts were pelleted by centrifugation at 3500 rpm in a GSA rotor (Sorvall) for 4 min at 40C. The crude chloroplast pellets were suspended in 400 ml of buffer B containing 0.6 M sorbitol, 0.01 M Tes (pH 7.8), 0.005 M EDTA, and 0.002 M 2,3-dihydroxy-1, 4-dithiobutane. After a minimum of 1 hr at 0C to reduce aggregation, the chloroplast suspension was filtered slowly through 5-,&m Nuclepore polycarbonate membranes with use of a syringe. Each 50-mm filter c...

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“…Plusieurs essais pr~liminaires ont montr~ qu'une purification des chloroplastes par centrifugation sur gradient discontinu de saccharose donne des organites ayant des spectres d'6mission plus altar, s que ceux de la figure lB. Afin de mieux preserver les chloroplastes, nous homog~n6isons rapidement les algues dans le tampon de Shephard et Levin [7], et nous r~coltons les chloroplastes (contamin~s par d'autres constituants cellulaires) sur un ffltre Millipore muni d'un pr~ffltre qui retient les fragments des patois cellulaires. Cette operation ne dure que quelques minutes.…”

Section: (3) Extraction Et Traitement Des Chloroplastesunclassified

La differenciation plastidale chez l'acetabulaire etudiee par l'emission de fluorescence a 77° K

Dujardin¹,

Bonotto²,

Sironval³

et al. 1975

Plant Science Letters

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BIOSYNTHESIS IN ISOLATED ACETABULARIA CHLOROPLASTS

Cited by 23 publications

References 25 publications

Photosynthate accumulation in solar-powered sea slugs - starving slugs survive due to accumulated starch reserves

Photosynthate accumulation in solar-powered sea slugs - starving slugs survive due to accumulated starch reserves

Tandemly repeated nonribosomal DNA sequences in the chloroplast genome of an Acetabularia mediterranea strain.

La differenciation plastidale chez l'acetabulaire etudiee par l'emission de fluorescence a 77° K

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