Genetic control of plasma membrane adhesion and fusion in Chlamydomonas gametes

1987 ◽  
Vol 88 (5) ◽  
pp. 613-621
Author(s):  
C.L. Forest
Keyword(s):  
Plasma Membrane ◽  
Chlamydomonas Reinhardtii ◽  
Genetic Control ◽  
Mating Type ◽  
Opposite Mating Type ◽  
Gamete Fusion ◽  
Gamete Interaction ◽  
Structure Interaction ◽  
Mating Structure ◽  
Membrane Adhesion

The final stages of gamete interaction in Chlamydomonas reinhardtii occur between the specialized plasma membrane organelles (mating structures) of opposite mating-type cells. A number of mutants affecting these interactions have been obtained in several laboratories; all have been defined as fusion-defective. This paper demonstrates that there are at least two genetically definable stages of mating-structure interaction: (1) the recognition/adhesion of mating structures, and (2) gamete fusion. The possibility that these two functions, the adhesion and subsequent fusion of mating structures, may be mating-type specific is raised, since of the seven independently isolated mutants analysed, all mutants defective in fusion are of mating-type (-), and only mating type (+) mutants show defects in adhesion.

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

1975 ◽  
Vol 67 (3) ◽  
pp. 623-637 ◽  
Author(s):  
U W Goodenough ◽  
R L Weiss
Keyword(s):  
Cell Wall ◽  
Chlamydomonas Reinhardtii ◽  
Mating Type ◽  
Experimental Manipulation ◽  
Wild Type ◽  
Opposite Mating Type ◽  
Mating Structure ◽  
Cell Wall Lysis ◽  
Gamete Formation ◽  
Mutant Strains

Cell fusion between mating type plus (mt+) and minus (mt-) gametes of Chlamydomonas 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 ml+ 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-l mt+ mutation are able to agglutinate but not fuse with mt- cells; the imp-l gametes are shown to have structurally defective mating structures that do not generate microfilaments in response to gametic agglutination.

scholarly journals The iso1 gene of Chlamydomonas is involved in sex determination.

1995 ◽  
Vol 6 (1) ◽  
pp. 87-95 ◽  
Author(s):  
A M Campbell ◽  
H J Rayala ◽  
U W Goodenough
Keyword(s):  
Sex Determination ◽  
Chlamydomonas Reinhardtii ◽  
Mating Type ◽  
Dna Sequences ◽  
Sexual Differentiation ◽  
Type Locus ◽  
Mating Structure ◽  
Mating Type Locus

Sexual differentiation in the heterothallic alga Chlamydomonas reinhardtii is controlled by two mating-type loci, mt+ and mt-, which behave as a pair of alleles but contain different DNA sequences. A mutation in the mt minus-linked imp11 gene has been shown previously to convert a minus gamete into a pseudo-plus gamete that expresses all the plus gametic traits except the few encoded by the mt+ locus. Here we describe the iso1 mutation which is unlinked to the mt- locus but is expressed only in minus gametes (sex-limited expression). A population of minus gametes carrying the iso1 mutation behaves as a mixture of minus and pseudo-plus gametes: the gametes isoagglutinate but they do not fuse to form zygotes. Further analysis reveals that individual gametes express either plus or minus traits: a given cell displays one type of agglutinin (flagellar glycoprotein used for sexual adhesion) and one type of mating structure. The iso1 mutation identifies a gene unlinked to the mating-type locus that is involved in sex determination and the repression of plus-specific genes.

Perithecial distribution patterns in standard and variant strains of Neurospora crassa

1981 ◽  
Vol 59 (12) ◽  
pp. 2610-2617 ◽  
Author(s):  
A. J. F. Griffiths ◽  
A. Rieck
Keyword(s):  
Neurospora Crassa ◽  
Genetic Control ◽  
Mating Type ◽  
Central Zone ◽  
Distribution Patterns ◽  
The Other ◽  
Clear Zone ◽  
Opposite Mating Type ◽  
Double Line ◽  
Inheritance Patterns

When crosses are made homozygous for the mutation fl, which completely eliminates conidiation, the patterns of sexual morphogenesis may be observed unobscured by effects due to conidia and conidial dispersal. In one cross, arbitrarily chosen as the standard, a striking double line of perithecia is seen, bordering a distinct clear central zone. Other crosses show a complex array of mating reactions, some involving an apparent invasion of one culture by nuclei of the opposite mating type, either through heterokaryotization or through overgrowth of one culture by the other. The width of the clear zone and the direction of invasion are variable and strain specific. The extent of heterokaryotization in the standard and variant crosses is discussed in relation to the situation found in other species. A complex genetic control of these reactions is indicated from inheritance patterns.

scholarly journals The Chlamydomonas Fus1 Protein Is Present on the Mating Type plus Fusion Organelle and Required for a Critical Membrane Adhesion Event during Fusion with minus Gametes

2003 ◽  
Vol 14 (6) ◽  
pp. 2530-2542 ◽  
Author(s):  
Michael J. Misamore ◽  
Surabhi Gupta ◽  
William J. Snell
Keyword(s):  
Genetic Analysis ◽  
Mating Type ◽  
Plasma Membranes ◽  
Molecular Mechanisms ◽  
External Surface ◽  
Early Step ◽  
Entire Surface ◽  
Gamete Fusion ◽  
Eukaryotic Genes ◽  
Membrane Adhesion

The molecular mechanisms of the defining event in fertilization, gamete fusion, remain poorly understood. The FUS1 gene in the unicellular, biflagellated green alga Chlamydomonas is one of the few sex-specific eukaryotic genes shown by genetic analysis to be essential for gamete fusion during fertilization. In Chlamydomonas, adhesion and fusion of the plasma membranes of activated mt+ and mt- gametes is accomplished via specialized fusion organelles called mating structures. Herein, we identify the endogenous Fus1 protein, test the idea that Fus1 is at the site of fusion, and identify the step in fusion that requires Fus1. Our results show that Fus1 is a ∼95-kDa protein present on the external surface of both unactivated and activated mt+ gametes. Bioassays indicate that adhesion between mating type plus and mating type minus fusion organelles requires Fus1 and that Fus1 is functional only after gamete activation. Finally, immunofluorescence demonstrates that the Fus1 protein is present as an apical patch on unactivated gametes and redistributes during gamete activation over the entire surface of the microvillous-like activated plus mating structure, the fertilization tubule. Thus, Fus1 is present on mt+ gametes at the site of cell-cell fusion and essential for an early step in the fusion process.

scholarly journals Cyclic AMP functions as a primary sexual signal in gametes of Chlamydomonas reinhardtii.

1987 ◽  
Vol 105 (5) ◽  
pp. 2279-2292 ◽  
Author(s):  
S M Pasquale ◽  
U W Goodenough
Keyword(s):  
Adenylate Cyclase ◽  
Chlamydomonas Reinhardtii ◽  
Mating Type ◽  
Cyclic Nucleotide ◽  
Actin Polymerization ◽  
Cyclic Nucleotide Phosphodiesterase ◽  
Intracellular Camp ◽  
Opposite Mating Type ◽  
Flagellar Membrane ◽  
Camp Levels

When Chlamydomonas reinhardtii gametes of opposite mating type are mixed together, they adhere by a flagella-mediated agglutination that triggers three rapid mating responses: flagellar tip activation, cell wall loss, and mating structure activation accompanied by actin polymerization. Here we show that a transient 10-fold elevation of intracellular cAMP levels is also triggered by sexual agglutination. We further show that gametes of a single mating type can be induced to undergo all three mating responses when presented with exogenous dibutyryl-cAMP (db-cAMP). These events are also induced by cyclic nucleotide phosphodiesterase inhibitors, which elevate endogenous cAMP levels and act synergistically with db-cAMP. Non-agglutinating mutants of opposite mating type will fuse efficiently in the presence of db-cAMP. No activation of mating events is induced by calcium plus ionophores, 8-bromo-cGMP, dibutyryl-cGMP, nigericin at alkaline pH, phorbol esters, or forskolin. H-8, an inhibitor of cyclic nucleotide-dependent protein kinase, inhibits mating events in agglutinating cells and antagonizes the effects of cAMP on non-agglutinating cells. Adenylate cyclase activity was detected in both the gamete cell body and flagella, with the highest specific activity displayed in flagellar membrane fractions. The flagellar membrane adenylate cyclase is preferentially stimulated by Mn++, unresponsive to NaF, GTP, GTP gamma S, AlF4-, and forskolin, and is inhibited by trifluoperazine. Cyclic nucleotide phosphodiesterase activity is also present in flagella. Our observations indicate that cAMP is a sufficient initial signal for all of the known mating reaction events in C. reinhardtii, and suggest that the flagellar cyclase and/or phosphodiesterase may be important loci of control for the agglutination-stimulated production of this signal.

ESCAPE FROM MATING-TYPE INCOMPATIBILITY IN BISEXUAL (A + a) NEUROSPORA HETEROKARYONS

1975 ◽  
Vol 17 (3) ◽  
pp. 441-449 ◽  
Author(s):  
A. M. DeLange ◽  
A. J. F. Griffiths
Keyword(s):  
Mating Type ◽  
Loss Of Function ◽  
Wild Type ◽  
Opposite Mating Type ◽  
Type Locus ◽  
Heterokaryon Incompatibility ◽  
Recessive Mutant ◽  
Type Rate ◽  
Wild Type Rate ◽  
Incompatibility Locus

In Neurospora crassa, strains of opposite mating type generally do not form stable heterokaryons because the mating type locus acts as a heterokaryon incompatibility locus. However, when one A and one a strain, having complementing auxotrophic mutants, are placed together on minimal medium, growth may occur, although the growth is generally slow. In this study, escape from such slow growth to that at a wild type or near-wild type rate was observed. The escaped cultures are stable heterokaryons, mostly having lost the mating type allele function from one component nucleus, so that the nuclear types are heterokaryon compatible. Either A or a mating type can be lost. This loss of function has been attributed to deletion since only one nuclear type could be recovered in all heterokaryons except one, but deletion spanning adjacent loci has been directly demonstrated in a minority of cases. Alternatively when one component strain is tol and the other tol+ (tol being a recessive mutant suppressing the heterokaryon incompatibility associated with mating type), escape may occur by the deletion or mutation of tol+, also resulting in heterokaryon compatibility. An induction mechanism for escape is speculated upon.

scholarly journals Characterization of novel genes induced by sexual adhesion and gamete fusion and of their transcriptional regulation in Chlamydomonas reinhardtii

2008 ◽  
Vol 49 (6) ◽  
pp. 981-993 ◽  
Author(s):  
T. Kubo ◽  
J. Abe ◽  
T. Oyamada ◽  
M. Ohnishi ◽  
H. Fukuzawa ◽  
...  
Keyword(s):  
Transcriptional Regulation ◽  
Chlamydomonas Reinhardtii ◽  
Novel Genes ◽  
Gamete Fusion

scholarly journals The Chlamydomonas Mating Type Plus Fertilization Tubule, a Prototypic Cell Fusion Organelle: Isolation, Characterization, and In Vitro Adhesion to Mating Type Minus Gametes

1997 ◽  
Vol 137 (7) ◽  
pp. 1537-1553 ◽  
Author(s):  
Nedra F. Wilson ◽  
Mary J. Foglesong ◽  
William J. Snell
Keyword(s):  
Cell Fusion ◽  
Mating Type ◽  
Plasma Membranes ◽  
Surface Proteins ◽  
Filamentous Actin ◽  
Mating Structure ◽  
Cell Protrusion ◽  
Isolation And Characterization ◽  
In Vitro Adhesion

In the biflagellated alga Chlamydomonas, adhesion and fusion of the plasma membranes of gametes during fertilization occurs via an actin-filled, microvillus-like cell protrusion. Formation of this ∼3-μm-long fusion organelle, the Chlamydomonas fertilization tubule, is induced in mating type plus (mt+) gametes during flagellar adhesion with mating type minus (mt−) gametes. Subsequent adhesion between the tip of the mt+ fertilization tubule and the apex of a mating structure on mt− gametes is followed rapidly by fusion of the plasma membranes and zygote formation. In this report, we describe the isolation and characterization of fertilization tubules from mt+ gametes activated for cell fusion. Fertilization tubules were detached by homogenization of activated mt+ gametes in an EGTA-containing buffer and purified by differential centrifugation followed by fractionation on sucrose and Percoll gradients. As determined by fluorescence microscopy of samples stained with a fluorescent probe for filamentous actin, the method yielded 2–3 × 106 fertilization tubules/μg protein, representing up to a 360-fold enrichment of these organelles. Examination by negative stain electron microscopy demonstrated that the purified fertilization tubules were morphologically indistinguishable from fertilization tubules on intact, activated mt+ gametes, retaining both the extracellular fringe and the internal array of actin filaments. Several proteins, including actin as well as two surface proteins identified by biotinylation studies, copurified with the fertilization tubules. Most importantly, the isolated mt+ fertilization tubules bound to the apical ends of activated mt− gametes between the two flagella, the site of the mt− mating structure; a single fertilization tubule bound per cell, binding was specific for gametes, and fertilization tubules isolated from trypsin-treated, activated mt+ gametes did not bind to activated mt− gametes.

scholarly journals GENETICS OF CHLAMYDOMONAS REINHARDTII DIPLOIDS. II. THE EFFECTS OF DIPLOIDY AND ANEUPLOIDY ON THE TRANSMISSION OF NON-MENDELIAN MARKERS

Genetics ◽  
1984 ◽  
Vol 107 (4) ◽  
pp. 563-576
Author(s):  
Eva M Eves ◽  
Kwen-Sheng Chiang
Keyword(s):  
Drug Resistance ◽  
Chloroplast Dna ◽  
Chlamydomonas Reinhardtii ◽  
Cell Line ◽  
Mating Type ◽  
Secondary Effect ◽  
Chloroplast Gene ◽  
A Cell ◽  
Resistance Markers ◽  
Normal Laboratory

ABSTRACT The transmission of two non-Mendelian drug resistance markers has been studied in crosses of Chlamydomonas reinhardtii involving diploids and aneuploids with different mating type genotypes. Under normal laboratory conditions for gametogenesis, mating and zygote maturation, the transmission pattern of the non-Mendelian markers sr-u-1 (resistance to streptomycin) and spr-u-1-27-3 (resistance to spectinomycin) is primarily determined by the mating type genotypes of the parental cells. Our results confirm and expand an earlier observation suggesting that an apparent codominant function of the female (mt  +) allele in regulating chloroplast gene transmission in meiosis appears to be distinct and separate from its recessive function in regulating mating behavior. The chloroplast DNA complement (as indexed by the number of extranuclear DNA-containing bodies) may exert a secondary effect on the transmission of these markers. Within a mating type group (mt+/mt- or mt-/mt-) a cell line with more chloroplast DNA tended to transmit its non-Mendelian markers more frequently than a cell line with less chloroplast DNA.

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