Autolyse der zellwand bei den gameten von Chlamydomonas reinhardii

Claes, Hedwig

doi:10.1007/bf00424874

Cited by 82 publications

(38 citation statements)

References 6 publications

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“…The pH shock procedure used in this paper was originally designed to isolate biologically active flagella (29) and is normally carried out in the presence of sucrose. However, when the sucrose was omitted, the agglutination factor was released into the medium (this paper) and the flagella became inactive (5,10). The fact that the mt' agglutination factor can be solubilized by lowering the pH to 4.3 for 1 min, or by an osmotic shock ( Table I), suggests that the plus factor is only loosely bound to the cell surface and is probably an extrinsic membrane protein.…”

Section: Discussionmentioning

confidence: 81%

Sexual Agglutination in the Unicellular Green Alga Chlamydomonas eugametos

Klis

Samson²,

Touw³

et al. 1985

Plant Physiol.

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Gametes of the unicellular green alga Chlamydomonas eugametos agglutinate via their flagella. The mating type plus agglutination factor was solubilized by relatively mild treatments such as a short pH shock or an osmotic shock indicating that it is an extrinsic 'membrane component. It was also extracted in the nonionic detergent Triton X-100. A simple two-step procedure consisting of gel filtration over Sepharose 4B-cross-linked followed by anion exchange chromatography of the void volume yielded an electrophoretically pure preparation of a single high molecular weight glycoprotein. The agglutination factor sedimented as a 93 S particle (assuming a density of 1.50) in sucrose gradients. This low value, compared with the high apparent molecular weight seen during gel filtration and electrophoresis, suggests that the agglutination factor is a rod-like molecule. This was confirmed by viewing rotary-shadowed preparations in the electron microscope. A population of long slender molecules was revealed (328 ± 20 nanometers), many of which had a knob at one end and a flexible region about one fourth of the length from the other end.Cell-cell recognition in plants plays a role in a remarkable range of phenomena including sexual reproduction, parasitism, grafting, and many others (15). The sexual agglutination process shown by gametes of Chlamydomonas represents a spectacular example of such a recognition process (11,27,28 . More recently, the isolation of the mtV agglutination factor was also reported (6, 24). In C. eugametos, a species that cannot sexually agglutinate with C. reinhardtii, the mtr agglutination factor has been purified and analyzed by Musgrave et al. (19) and by Homan (12). In this paper we report the purification of the mt+ agglutination factor ofthis species, and show that it is a long linearglycoprotein. MATERIALS AND METHODSCell Cultures. Chlamydomonas eugametos strains 11-5/9 (mt+) and 11-5/10 (mtr) from the Sammlung von Algenkulturen, Gottingen, Federal Republic of Germany, were cultivated in Petri dishes on agar-containing medium in a 12-h light/12-h dark regimen as described by Mesland (17). Gamete suspensions were obtained by flooding 2-to 3-week-old cultures with distilled H20 just before the start of the dark period. They were harvested the following light period. A Petri dish culture contained on the average 2.5 x 108 cells. Suspensions of vegetative cells were obtained by flooding with 0.5% (w/v) NH4Cl (23).Detergent Extraction of mt' Agglutination Factor. Gamete suspensions were centrifuged at 5°C at 1500g for 15 min. The cells were resuspended in ice-cold 0.1I% (w/v) Triton X-100 (1 ml/culture) and gently shaken at 5°C for 1 h. The suspension was then centrifuged at 48,000g for 30 min. The supernatant was collected and mixed with extensively washed Amberlite XAD-2 (20 g wet weight/100 ml) to remove Triton X-100 (4). The Amberlite suspension was shaken at 5°C for 15 min and filtered to remove the Amberlite. Fresh Amberlite was added to the filtrate and the procedure was repeated. T...

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Section: Discussionmentioning

confidence: 81%

Sexual Agglutination in the Unicellular Green Alga Chlamydomonas eugametos

Klis

Samson²,

Touw³

et al. 1985

Plant Physiol.

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“…FIGURE 14 Negatively stained cell wall from which a mated gamete has emerged through the ruptured anterior end. x 10,000. matings involving the nonagglutinating strains i m p -5 , irnp-7, and i m p -8 , nor does it occur when wild-type ceils are rendered nonagglutinable by trypsinization (26), as noted also by Claes (2).…”

Section: Figure 12mentioning

confidence: 97%

“…1, an interaction that appears to involve surface components of the flagellar membranes (1,24). Four events follow in quick succession: (a) a lytic activity digests the cell walls so that gametes are converted to naked protoplasts (2): (b) a cytoplasmic protuberance [the fertilization tubule (4)] extends from the mt+ cell surface (Fig. 1, tong arrow), an event mediated by the specialized mating structure first described by Friedmann et al (4); (c) the fertilization tubule makes contact with an mt-mating structure to form a narrow cytoplasmic bridge (4); and (d) the bridge expands in diameter until the mating pair is transformed into a single quadriflagellate zygote, an event that can be termed zygotic cell fusion (see Fig.…”

mentioning

confidence: 99%

Gametic differentiation in Chlamydomonas reinhardtii. III. Cell wall lysis and microfilament-associated mating structure activation in wild-type and mutant strains.

Goodenough¹,

Weiss²

1975

The Journal of Cell Biology

121

100

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Cell fusion between mating type plus (mr +) and minus (rot-) gametes ofChlamydomonas reinhardtii is analyzed structurally and subjected to experimental manipulation. Cell wall lysis, a necessary prelude to fusion, is shown to require flagellar agglutination between competent gametes; glutaraldehyde-fixed gametes ("corpses") of one mating type will elicit both agglutination and cell wall lysis in the opposite mating type, whereas nonagglutinating impotent (imp) mutant strains are without effect. The fusion process is mediated by a narrow fertilization tubule which extends from the mt+ gamete and establishes contact with the mt-gamete. Formation of the tubule requires the "activation" of a specialized mating structure associated with the mt + cell membrane; activation causes microfilaments to polymerize from the mating structure into the growing fertilization tubule. Mating structure activation is shown to depend on gametic flagellar agglutination; isoagglutination mediated by the lectin concanavalin A has no effect. Gametes carrying the imp-I mt+ mutation are able to agglutinate but not fuse with rotcells; the imp-1 gametes are shown to have structurally defective mating structures that do not generate microfilaments in response to gametic agglutination.The mating reaction of the biflagellate alga Chlamydomonas reinhardtii involves an elaborate sequence of events that can be presumed to depend on precise levels of cellular communication. The reaction is initiated by an agglutination between the flagellar tips of mating type plus (mr +) and minus (mr-) gametes (18), as illustrated in Fig. 1, an interaction that appears to involve surface components of the flagellar membranes (1, 24). Four events follow in quick succession: (a) a lytic activity digests the cell walls so that gametes are converted to naked protoplasts (2): (b) a cytoplasmic protuberance [the fertilization tubule (4)] extends from the mt+ cell surface (Fig. 1, tong arrow), an event mediated by the specialized mating structure first described by Friedmann et al. (4); (c) the fertilization tubule makes contact with an mt-mating structure to form a narrow cytoplasmic bridge (4); and (d) the bridge expands in diameter until the mating pair is transformed into a single quadriflagellate zygote, an event that can be termed zygotic cell fusion (see Fig. I). Quadriflagellate zygotes typically appear within 5 rain after mt § and rot-gametes are mixed; all of these events must therefore occur in a rapid and highly coordinated fashion.

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“…Flagellar adhesion between mt + and mt-gametes initiates a sexual signal leading to formation of mating structures involved in cell fusion and activation of the cell wall degrading enzyme, lysin (7). Chlamydomonas is particularly useful for studies on cell contact-mediated signaling because it is a unicellular organism that is amenable to genetic analysis and mutants blocked at several stages of fertilization are already available (10).…”

mentioning

confidence: 99%

Regulated secretion of a serine protease that activates an extracellular matrix-degrading metalloprotease during fertilization in Chlamydomonas.

Snell

Eskue

Buchanan

1989

The Journal of Cell Biology

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Abstract. During fertilization in the biflagellated alga, Chlamydomonas reinhardtii, gametes of opposite mating types adhere to each other via agglutinin molecules located on their flagellar surfaces, generating a sexual signal that induces several cellular responses including cell wall release. This cell contact-generated signal is mediated by cAMP and release of the wall, which is devoid of cellulose and contains several hydroxyproline-rich glycoproteins, is due to the activation of a metalloprotease, lysin. Although we originally assumed that lysin would be stored intracellulady in a compartment structurally separate from its substrate, recently we showed that lysin is stored in the periplasm as an inactive, higher relative molecular mass precursor, prolysin (Buchanan, M. J., S. H.

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Autolyse der zellwand bei den gameten von Chlamydomonas reinhardii

Cited by 82 publications

References 6 publications

Sexual Agglutination in the Unicellular Green Alga Chlamydomonas eugametos

Sexual Agglutination in the Unicellular Green Alga Chlamydomonas eugametos

Gametic differentiation in Chlamydomonas reinhardtii. III. Cell wall lysis and microfilament-associated mating structure activation in wild-type and mutant strains.

Regulated secretion of a serine protease that activates an extracellular matrix-degrading metalloprotease during fertilization in Chlamydomonas.

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