Wall loss and origin of soluble carbohydrates during mating of Chlamydomonas reinhardi

Solter, Kenneth M.; Chow, Hsian-Chia; Ray, Darryl A.; Gibor, Aharon

doi:10.1016/0031-9422(80)83009-3

Cited by 6 publications

(2 citation statements)

References 30 publications

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“…Such studies are easiest to perform with a plant in which protoplasts can be readily obtained in quantities suitable for enzyme extraction, and which rapidly and synchronously resynthesize cell walls. This can be achieved in the unicellular green alga Chlamydomonas reinhardii, which possesses a hydroxyproline-rich cell wall (Roberts, 1974;Solter et al, 1980). The extracellular matrix can be easily solubilized, and the resulting protoplasts will rapidly resynthesize cell walls.…”

Section: Introductionmentioning

confidence: 99%

Characterization of a low-relative-molecular-mass prolyl 4-hydroxylase from the green alga Chlamydomonas reinhardii

Kaska¹,

Günzler²,

Kivirikko³

et al. 1987

Biochemical Journal

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Prolyl 4-hydroxylase was partially purified and characterized from the unicellular green alga, Chlamydomonas reinhardii. This enzyme differed from all the animal and plant prolyl 4-hydroxylases studied so far in that its Mr was only about 40,000 by gel filtration, being thus less than one-sixth of those determined for the vertebrate and higher-plant enzymes. The algal enzyme did not hydroxylate to any significant extent chick-embryo protocollagen or triple-helical (Pro-Pro-Gly)10, whereas a low hydroxylation rate was found with denatured (Pro-Pro-Gly)10. Poly(L-proline), which is an effective inhibitor of the vertebrate enzymes but acts as a substrate for some higher-plant enzymes, was a good substrate. In the absence of poly(L-proline) the enzyme catalysed an uncoupled decarboxylation of 2-oxoglutarate. Studies of the Km values for the co-substrates and cofactors and the specificity of the 2-oxoglutarate requirement, as well as inhibition studies with selected 2-oxoglutarate analogues, suggested that the catalytic site of the algal enzyme is similar to, but not identical with, those of the vertebrate enzymes. The existence of distinct similarities was further demonstrated by an inhibition of the algal enzyme activity with a monoclonal antibody to the beta-subunit of human prolyl 4-hydroxylase. The amount of prolyl 4-hydroxylase activity in the algal cells was not altered by signals which recognize the presence or absence of the cell wall, as determined in studies on experimental cell-wall regeneration and wall-less mutants.

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Section: Introductionmentioning

confidence: 99%

Characterization of a low-relative-molecular-mass prolyl 4-hydroxylase from the green alga Chlamydomonas reinhardii

Kaska¹,

Günzler²,

Kivirikko³

et al. 1987

Biochemical Journal

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“…Gametes of opposite mating types interact by their flagellar surfaces by means of species-, gamete-, and mating type (mr)specific agglutinin molecules (1,39); this reaction has been intensively studied as a model system for specific cell-cell interactions. Flagellar membrane contact is followed by reorientation of the flagella (6,32,36), flagellar tip activation (38), transmission of a signal from the flagella to the cell bodies (14,64), loss of cell walls due to release of a specific lysin (53,60,65), activation of a specific mating structure on each partner (20,21), cell-cell fusion (67), and de-adhesion of the flagellar surfaces (61,62). This carefully programmed sequence of events can be completed in under 5 min, resulting in a heterokaryon that will later become a zygote after flagellar resorption and nuclear fusion.…”

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Transient increase in calcium efflux accompanies fertilization in Chlamydomonas.

Bloodgood¹,

Levin²

1983

The Journal of Cell Biology

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Mating in Chlamydomonas is a complex process initiated by contact of gametic flagellar surfaces, resulting in transmission of a signal from the flagella to the cell bodies. This signal triggers later events of cell wall loss, mating structure activation, and cell-cell fusion. Little is known about the nature of the signal or the role of Ca in these events. It was found that extracellular Ca is not necessary for successful mating in Chlamydomonas. However, cells will take up Ca from the medium in a linear manner for many hours and will accumulate micromolar concentrations, presumably by sequestering Ca within intracellular storage sites. If gametic cells of one mating type (preloaded with 45Ca) are mated with gametes of the opposite mating type (preloaded with unlabeled calcium), there is a rapid, transient increase in calcium efflux rate (20 times that of the control) that lasts ,--6 min. This effect is not associated with cell-cell fusion, since the same observation is made if (+) gametes preloaded with 45-Ca are agglutinated by isolated flagella from (-) gametes preloaded with unlabeled Ca. Other experiments have shown that the increased efflux rate is not a simple consequence of cell wall release. Ca efflux in unmated gametes is greatly reduced in deflagellated cells, suggesting that much of the Ca movement is associated with the flagellar membrane. Although signaling itself may involve Ca fluxes across the flagellar membrane, it is also possible that a consequence of signaling is release of Ca from intracellular storage sites (perhaps functional equivalents of the sarcoplasmic reticulum). The observed transient increase in Ca efflux rate may reflect a transient increase in the cytoplasmic free-Ca concentration. This increase in cytoplasmic Ca may regulate the later events in mating (such as cell wall release and mating structure activation).Ca has been frequently implicated in the early events of fertilization, particularly in marine eggs (see references 13, 25, 58, 68 for reviews). In these systems, external Ca is generally necessary for sperm activation, but is not necessary for fertilization of eggs by previously acrosome-reacted sperm (55, 56). Fertilization results in a transient increase in free cytoplasmic Ca, presumably released from some intracellular membrane-bounded compartment. The increase in cytoplasmic free-Ca concentration induces the cortical granule reaction, which results in formation of the fertilization membrane from the vitelline envelope.Mating events in Chlamydomonas have been the subject of intense study (17,19,22). Chlamydomonas is an isogamous green alga in which the gametes of the two different mating types are of equal size and of almost identical structure. Gametes of opposite mating types interact by their flagellar surfaces by means of species-, gamete-, and mating type (mr)-specific agglutinin molecules (1, 39); this reaction has been intensively studied as a model system for specific cell-cell interactions. Flagellar membrane contact is followed by reorientation of ...

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Initiation of cell wall lysis in gametes of Chlamydomonas reinhardi by isolated flagella of the complementary mating type*1

Kaska

Gibor

1982

Experimental Cell Research

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Wall loss and origin of soluble carbohydrates during mating of Chlamydomonas reinhardi

Cited by 6 publications

References 30 publications

Characterization of a low-relative-molecular-mass prolyl 4-hydroxylase from the green alga Chlamydomonas reinhardii

Characterization of a low-relative-molecular-mass prolyl 4-hydroxylase from the green alga Chlamydomonas reinhardii

Transient increase in calcium efflux accompanies fertilization in Chlamydomonas.

Initiation of cell wall lysis in gametes of Chlamydomonas reinhardi by isolated flagella of the complementary mating type*1

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