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  • 1
    Electronic Resource
    Electronic Resource
    Endogenous oscillator controls surface density of mating receptors in Chlamydomonas eugametos (1988)
    Springer
    Sexual plant reproduction 1 (1988), S. 46-50 
    Details
    ISSN: 1432-2145
    Keywords: Agglutinins ; Chlamydomonas ; Circadian rhythm ; Flagella ; Gametes ; Receptors(mating)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We describe a circadian rhythm in the surface density of receptors that play a dominant role in the mating process of the unicellular green alga Chlamydomonas eugametos.These receptors — called agglutinins — are large glycoproteins extrinsically bound to the membrane of gamete flagella. We found circadian fluctuations in their density. Since inhibition of protein synthesis affected the agglutinin density without a lag period at any time,we conclude that the density was dependent on de novo synthesis and that the fluctuations in density are caused by circadian oscillations in the rate of agglutinin synthesis. This phenomenon evidently underlies the pronounced endogenous rhythm in mating competence that we described previously (Demets et al. 1987). Finally, we speculate on the nature of the time keeping mechanism that is generating these rhythmic events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227022
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Cell-cell coordination in conjugatingChlamydomonas gametes (1990)
    Springer
    Protoplasma 155 (1990), S. 188-199 
    Details
    ISSN: 1615-6102
    Keywords: Adhesion ; Agglutinin ; Chlamydomonas ; Conjugation ; Flagellum ; Gamete ; Signalling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary During conjugation, complementaryChlamydomonas gametes [mating type plus (mt+) and mating type minus (mt−)] are mutually attached via specific adhesion molecules, called agglutinins, which are located at the surface of the flagella. By these contacts the gametes are stimulated to fuse. It is demonstrated that fusion is preceded by a compulsary sequence of events: first, the flagellar swimming beat is arrested, next the flagellar contact is reinforced and finally, the position of the cell bodies is adjusted to permit fusion. Evidence is presented that each consecutive step of the mating process requires a higher level in cell-cell signalling, which is obtained by the formation of additional agglutinin contacts. It is shown that the mt+ and mt− traverse their conjugation process in synchrony, probably because the two sexes acquire new agglutinin contacts at equal rates. It is proposed that this symmetrical behavior is due to the complementarity of the mt+ and mt− agglutinin molecules. A scenario of the conjugation process inC. eugametos, incorporating the recent findings, is provided.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322628
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Turnover and transport of agglutinins in conjugatingChlamydomonas gametes (1990)
    Springer
    Protoplasma 155 (1990), S. 200-209 
    Details
    ISSN: 1615-6102
    Keywords: Cell adhesion,Chlamydomonas ; Flagellum ; Gamete activation ; Receptor turnover ; Sexual agglutinins ; Signalling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary During gamete-gamete adhesion in the unicellular green algaChlamydomonas eugametos, the sexual adhesion molecules or agglutinins that are located on the flagella are subject to tip-oriented migration and rapid inactivation. It is demonstrated that sexual adhesiveness is maintained by incorporation of additional agglutinins, recruited from a cellular pool. The location of this reservoir is unknown but, as indicated by its insensitivity to the chaotropic agent guanidine thiocyanate, it appears to be distinct from the large amount of agglutinins on the plasma membrane of the cell body. By viewing flagella of conjugating gametes in a confocal scanning laser microscope after immuno-labelling of the agglutinins, evidence was obtained for a linear arrangement of the agglutinins in two rows on the flagellar surface. This suggests that after insertion at the base of the flagellum, the agglutinins follow linear tracks to the tip and that the transport system is confined to two longitudinal domains. It is estimated that the half-life of flagellar agglutinins drops from 1–2 h in nonconjugating gametes to 1 min during conjugation, which suggests that after incorporation at the flagellar base, the agglutinins migrate to the tip with a velocity of 100 nm/s. Presumably after arrival at the tip, the molecules are inactivated. It is postulated that rapid turnover and transport of agglutinins are required for optimal signalling between partner gametes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322629
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Cell-cell adhesion in conjugatingChlamydomonas gametes: a self-enhancing process (1988)
    Springer
    Protoplasma 145 (1988), S. 27-36 
    Details
    ISSN: 1615-6102
    Keywords: Adhesion ; Agglutinin ; Chlamydomonas ; Flagellum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The flagellar adhesiveness of gametes ofChlamydomonas eugametos increases during conjugation such that the cell-cell contacts are intensified. The rise in adhesiveness is due to an increase in agglutinin exposure which can be visualized by immunolabeling. The adhesiveness in the one cell is stimulated by the agglutinins of the adherent partner cell, and vice versa. Thus, sexual cell-cell adhesion is a self-enhancing process. In addition, it is shown that the gametes are able to activate potential partners at distance via agglutinin-rich vesicles which they shed into their environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01323253
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    Paper (German National Licenses)
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