The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
Syed Qasim Raza - One of the best experts on this subject based on the ideXlab platform.
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53bp1 represses mitotic catastrophe in syncytia elicited by the hiv 1 envelope
Cell Death & Differentiation, 2010Co-Authors: Jl Perfettini, Roberta Nardacci, Claire Seror, Syed Qasim RazaAbstract:p53 binding protein-1 (53BP1) participates in checkpoint signaling during the DNA damage response (DDR) and during mitosis. In this study we report that 53BP1 aggregates in nuclear foci within syncytia elicited by the human immunodeficiency virus (HIV)-1 envelope. 53BP1 aggregation occurs as a consequence of nuclear fusion (Karyogamy (KG)). It colocalizes partially with the promyelomonocytic leukemia protein (PML), and the ataxia telangiectasia mutated kinase (ATM), the two components of the DDR that mediate apoptosis induced by the HIV-1 envelope. ATM-dependent phosphorylation of 53BP1 on serines 25 and 1778 (53BP1S25P and 53BP1S1778P) occurs at these DNA damage foci. 53BP1S25P was also detected in syncytia present in the lymph nodes or frontal brain sections from HIV-1-infected carriers, as well as in peripheral blood mononucleated cells from HIV-1-infected individuals, correlating with viral load. Knockdown of 53BP1 caused HIV-1 envelope-induced syncytia to enter abnormal mitoses, leading to their selective destruction through mitochondrion-dependent and caspase-dependent pathways. In conclusion, depletion of 53BP1 triggers the demise of HIV-1-elicited syncytia through mitotic catastrophe.
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53BP1 represses mitotic catastrophe in syncytia elicited by the HIV-1 envelope
'Springer Science and Business Media LLC', 2010Co-Authors: Jl Perfettini, Roberta Nardacci, Claire Seror, Syed Qasim Raza, S. Sepe, H. Saidi, F. Brottes, A. Amendola, F. Subra, F. Del NonnoAbstract:p53 binding protein-1 (53BP1) participates in checkpoint signaling during the DNA damage response (DDR) and during mitosis. In this study we report that 53BP1 aggregates in nuclear foci within syncytia elicited by the human immunodeficiency virus (HIV)-1 envelope. 53BP1 aggregation occurs as a consequence of nuclear fusion (Karyogamy (KG)). It colocalizes partially with the promyelomonocytic leukemia protein (PML), and the ataxia telangiectasia mutated kinase (ATM), the two components of the DDR that mediate apoptosis induced by the HIV-1 envelope. ATM-dependent phosphorylation of 53BP1 on serines 25 and 1778 (53BP1S25P and 53BP1S1778P) occurs at these DNA damage foci. 53BP1S25P was also detected in syncytia present in the lymph nodes or frontal brain sections from HIV-1-infected carriers, as well as in peripheral blood mononucleated cells from HIV-1-infected individuals, correlating with viral load. Knockdown of 53BP1 caused HIV-1 envelope-induced syncytia to enter abnormal mitoses, leading to their selective destruction through mitochondrion-dependent and caspase-dependent pathways. In conclusion, depletion of 53BP1 triggers the demise of HIV-1-elicited syncytia through mitotic catastrophe. Cell Death and Differentiation (2010) 17, 811-820; doi:10.1038/cdd.2009.159; published online 30 October 200
Jl Perfettini - One of the best experts on this subject based on the ideXlab platform.
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53bp1 represses mitotic catastrophe in syncytia elicited by the hiv 1 envelope
Cell Death & Differentiation, 2010Co-Authors: Jl Perfettini, Roberta Nardacci, Claire Seror, Syed Qasim RazaAbstract:p53 binding protein-1 (53BP1) participates in checkpoint signaling during the DNA damage response (DDR) and during mitosis. In this study we report that 53BP1 aggregates in nuclear foci within syncytia elicited by the human immunodeficiency virus (HIV)-1 envelope. 53BP1 aggregation occurs as a consequence of nuclear fusion (Karyogamy (KG)). It colocalizes partially with the promyelomonocytic leukemia protein (PML), and the ataxia telangiectasia mutated kinase (ATM), the two components of the DDR that mediate apoptosis induced by the HIV-1 envelope. ATM-dependent phosphorylation of 53BP1 on serines 25 and 1778 (53BP1S25P and 53BP1S1778P) occurs at these DNA damage foci. 53BP1S25P was also detected in syncytia present in the lymph nodes or frontal brain sections from HIV-1-infected carriers, as well as in peripheral blood mononucleated cells from HIV-1-infected individuals, correlating with viral load. Knockdown of 53BP1 caused HIV-1 envelope-induced syncytia to enter abnormal mitoses, leading to their selective destruction through mitochondrion-dependent and caspase-dependent pathways. In conclusion, depletion of 53BP1 triggers the demise of HIV-1-elicited syncytia through mitotic catastrophe.
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53BP1 represses mitotic catastrophe in syncytia elicited by the HIV-1 envelope
'Springer Science and Business Media LLC', 2010Co-Authors: Jl Perfettini, Roberta Nardacci, Claire Seror, Syed Qasim Raza, S. Sepe, H. Saidi, F. Brottes, A. Amendola, F. Subra, F. Del NonnoAbstract:p53 binding protein-1 (53BP1) participates in checkpoint signaling during the DNA damage response (DDR) and during mitosis. In this study we report that 53BP1 aggregates in nuclear foci within syncytia elicited by the human immunodeficiency virus (HIV)-1 envelope. 53BP1 aggregation occurs as a consequence of nuclear fusion (Karyogamy (KG)). It colocalizes partially with the promyelomonocytic leukemia protein (PML), and the ataxia telangiectasia mutated kinase (ATM), the two components of the DDR that mediate apoptosis induced by the HIV-1 envelope. ATM-dependent phosphorylation of 53BP1 on serines 25 and 1778 (53BP1S25P and 53BP1S1778P) occurs at these DNA damage foci. 53BP1S25P was also detected in syncytia present in the lymph nodes or frontal brain sections from HIV-1-infected carriers, as well as in peripheral blood mononucleated cells from HIV-1-infected individuals, correlating with viral load. Knockdown of 53BP1 caused HIV-1 envelope-induced syncytia to enter abnormal mitoses, leading to their selective destruction through mitochondrion-dependent and caspase-dependent pathways. In conclusion, depletion of 53BP1 triggers the demise of HIV-1-elicited syncytia through mitotic catastrophe. Cell Death and Differentiation (2010) 17, 811-820; doi:10.1038/cdd.2009.159; published online 30 October 200
Takashi Okamoto - One of the best experts on this subject based on the ideXlab platform.
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polyspermy in angiosperms its contribution to polyploid formation and speciation
Molecular Reproduction and Development, 2020Co-Authors: Erika Toda, Takashi OkamotoAbstract:: Polyploidization has played a major role in the long-term diversification and evolutionary success of angiosperms. Triploid formation among diploid plants, which is generally considered to be achieved by fertilization of an unreduced gamete with a reduced one, has been accepted as a means of polyploid production. In addition, it has been supposed that polyspermy also contributes to the triploid formation in maize, wheat, and some orchids; however, such a mechanism has been considered uncommon because reproducing the polyspermic situation and unambiguously investigating developmental profiles of polyspermic zygotes are difficult. To overcome these problems, rice polyspermic zygotes have been successfully produced by electrofusion of an egg cell with two sperm cells, and their developmental profiles have been monitored. The triploid zygotes progress through Karyogamy and divide into two-celled embryos via a typical bipolar mitotic division; the two-celled embryos further develop into triploid plants, indicating that polyspermic plant zygotes, unlike those of animals, can develop normally. Furthermore, progenies consisting of triparental genetic materials have been successfully obtained in Arabidopsis through the pollination of two different kinds of male parents with a female parent. These different pieces of evidence for development and emergence of polyspermic zygotes in vitro and in planta suggest that polyspermy is a key event in polyploidization and species diversification.
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sperm entry into the egg cell induces the progression of Karyogamy in rice zygotes
Plant and Cell Physiology, 2019Co-Authors: Yukinosuke Ohnishi, Iwao Kokubu, Tetsu Kinoshita, Takashi OkamotoAbstract:Karyogamy is a prerequisite event for plant embryogenesis, in which dynamic changes in nuclear architecture and the establishment of appropriate gene expression patterns must occur. However, the precise role of the male and female gametes in the progression of Karyogamy still remains elusive. Here, we show that the sperm cell possesses the unique property to drive steady and swift nuclear fusion. When we fertilized egg cells with sperm cells in vitro, the immediate fusion of the male and female nuclei in the zygote progressed. This rapid nuclear fusion did not occur when two egg cells were artificially fused. However, the nuclear fusion of two egg nuclei could be accelerated by additional sperm entry or the exogenous application of calcium, suggesting that possible increase of cytosolic Ca2+ level via sperm entry into the egg cell efficiently can facilitate Karyogamy. In contrast to zygotes, the egg-egg fusion cells failed to proliferate beyond an early developmental stage. Our transcriptional analyses also revealed the rapid activation of zygotic genes in zygotes, whereas there was no expression in fused cells without the male contribution. Thus, the male sperm cell has the ability to cause immediate Karyogamy and to establish appropriate gene expression patterns in the zygote.
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Nuclear migration during Karyogamy in rice zygotes is mediated by continuous convergence of actin meshwork toward the egg nucleus
Journal of Plant Research, 2017Co-Authors: Yukinosuke Ohnishi, Takashi OkamotoAbstract:Fertilization is comprised of two sequential fusion processes; plasmogamy and Karyogamy. Karyogamy completes with migration and fusion of the male and female nuclei in the fused cell. In animals, microtubules organized by the centrosome control female/male pronuclei migration. In contrast, the nuclear migration in fused gametes of angiosperms is controlled by actin filaments, but the mechanism that regulates actin filament-dependent nuclear migration is not clear. In this study, we prepared fused rice ( Oryza sativa L.) gametes/zygotes using in vitro fertilization and observed the spatial and temporal movements of actin filaments and sperm nuclei. Our results show that actin filaments in egg cells form a meshwork structure surrounding the nuclei. Quantitative analysis of the actin meshwork dynamics suggests that actin meshwork converges toward the egg nucleus. In egg cells fused with sperm cells, actin filaments appeared to interact with a portion of the sperm nuclear membrane. The velocity of the actin filaments was positively correlated with the velocity of the sperm nucleus during Karyogamy. These results suggest that sperm nuclear membrane and actin filaments physically interact with each other during Karyogamy, and that the sperm nucleus migrates toward the egg nucleus through the convergence of the actin meshwork. Interestingly, actin filament velocity increased promptly after gamete fusion and was further elevated during nuclear fusion. In addition to the migration of gamete nuclei, convergence of actin meshwork may also be critical during early zygotic developments.
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Karyogamy in rice zygotes actin filament dependent migration of sperm nucleus chromatin dynamics and de novo gene expression
Plant Signaling & Behavior, 2015Co-Authors: Yukinosuke Ohnishi, Takashi OkamotoAbstract:In angiosperms, the fusion of a sperm cell with an egg cell, termed plasmogamy, triggers egg activation. Then, Karyogamy, migration of the sperm nucleus toward the egg nucleus and their subsequent nuclear fusion, progresses, and de novo gene expression from the zygotic genome is initiated for early embryogenesis. Therefore, Karyogamy is an important post-fusion event that bridges egg activation and de novo gene expression in fused gametes/zygotes. In this study, we monitored the progression of Karyogamy in rice zygotes produced by in vitro fusion. The results indicated that the sperm nucleus migrated adjacent to the egg nucleus via an actin cytoskeleton, and the egg chromatin then appeared to move unidirectionally into the sperm nucleus through a possible nuclear connection. An enlargement of the sperm nucleus accompanied this possible chromatin remodeling. Then, 30–70 min after fusion, the sperm chromatin began to decondense, and Karyogamy was completed. The development of early rice zygotes from plasmog...
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Dynamics of Male and Female Chromatin during Karyogamy in Rice Zygotes
Plant Physiology, 2014Co-Authors: Yukinosuke Ohnishi, Rina Hoshino, Takashi OkamotoAbstract:In angiosperms, the conversion of an egg cell into a zygote involves two sequential gametic processes: plasmogamy, the fusion of the plasma membranes of male and female gametes, and Karyogamy, the fusion of the gametic nuclei. In this study, the nuclei and nuclear membranes of rice (Oryza sativa) gametes were fluorescently labeled using histones 2B-green fluorescent protein/red fluorescent protein and Sad1/UNC-84-domain protein2-green fluorescent protein, respectively, which were heterologously expressed. These gametes were fused in vitro to produce zygotes, and the nuclei and nuclear membranes in the zygotes were observed during Karyogamy. The results indicated that the sperm nucleus migrates adjacent to the egg nucleus 5 to 10 min after plasmogamy via an actin cytoskelton, and the egg chromatin then appears to move unidirectionally into the sperm nucleus through a possible nuclear connection. The enlargement of the sperm nucleus accompanies this possible chromatin remodeling. Then, 30 to 70 min after fusion, the sperm chromatin begins to decondense with the completion of Karyogamy. Based on these observations, the development of early rice zygotes from plasmogamy to Karyogamy was divided into eight stages, and using reverse transcription PCR analyses, paternal and de novo synthesized transcripts were separately detected in zygotes at early and late Karyogamy stages, respectively.
Terunobu Ichimura - One of the best experts on this subject based on the ideXlab platform.
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Spindle formation in Karyogamy-blocked zygotes of the isogamous brown alga Scytosiphon lomentaria (Scytosiphonales, Phaeophyceae)
European Journal of Phycology, 2000Co-Authors: Chikako Nagasato, Taizo Motomura, Terunobu IchimuraAbstract:The first spindle formation in Karyogamy-blocked zygotes in the isogamous brown alga Scytosiphon lomentaria was studied by electron and immunofluorescence microscopy using anti-centrin and anti-β-tubulin antibodies. Zygotes blocked in Karyogamy by incubation at high temperature (22 °C) were compared with normal zygotes incubated at 14 °C. In normal zygotes, after the disappearance of female gamete centrioles, centrioles from the male gamete duplicated and migrated to both poles in the metaphase, and a bipolar spindle was formed. The nuclear envelope was almost intact except at the poles. In Karyogamy-blocked zygotes of S. lomentaria, both DNA synthesis and chromosomal condensation occurred in the male and female nuclei. A bipolar mitotic spindle with a pair of centrioles at each of two poles could be observed in the male nucleus, but not in the female nucleus. In some cases, after a pair of centrioles derived from the male gamete duplicated and separated, one of the two pairs migrated towards the female n...
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Karyogamy BLOCK BY HEAT STRESS IN THE FERTILIZATION OF BROWN ALGAE
Journal of Phycology, 1999Co-Authors: Chikako Nagasato, Taizo Motomura, Terunobu IchimuraAbstract:Karyogamy was inhibited by heat stress in zygotes of Scytosiphon lomentaria (Lyngbye) Link (isogamy), Cutleria cylindrica Okamura (anisogamy), and Fucus distichus subsp. evanescens (C. Agardh) Powell (oogamy). Although high temperatures did not inhibit migration of the male and female nuclei, nuclear envelope fusion was blocked. The ultrastructural stage at which Karyogamy was inhibited varied among these species. In S. lomentaria, the outer membranes fused with each other, but the inner membranes did not fuse. Partial fusion of the nuclear envelope occurred in C. cylindrica. In F. distichus, the block of Karyogamy at high temperature was incomplete, and nuclear fusion proceeded gradually. The block to Karyogamy in S. lomentaria zygotes was reversible, and Karyogamy proceeded when zygotes were transferred from 22° to 14° C. Experiments using inhibitors suggested that proteins that might be formed de novo after fertilization do not participate in Karyogamy or its inhibition at either 14° or 22° C.
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Karyogamy follows plasmogamy in the life cycle of derbesia tenuissima chlorophyta
Phycologia, 1998Co-Authors: Taizo Motomura, Terunobu IchimuraAbstract:AbstractFertilization in a multinucleate siphonous green alga, Derbesia tenuissima (Moris et De Notaris) Crouan, was studied using light, fluorescence, and electron microscopy. The male nucleus was...
Mark D Rose - One of the best experts on this subject based on the ideXlab platform.
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distinct roles for key Karyogamy proteins during yeast nuclear fusion
Molecular Biology of the Cell, 2009Co-Authors: Shu Shen, Patricia G Melloy, Erin White, Mark D RoseAbstract:During yeast mating, cell fusion is followed by the congression and fusion of the two nuclei. Proteins required for nuclear fusion are found at the surface (Prm3p) and within the lumen (Kar2p, Kar5p, and Kar8p) of the nuclear envelope (NE). Electron tomography (ET) of zygotes revealed that mutations in these proteins block nuclear fusion with different morphologies, suggesting that they act in different steps of fusion. Specifically, prm3 zygotes were blocked before formation of membrane bridges, whereas kar2, kar5, and kar8 zygotes frequently contained them. Membrane bridges were significantly larger and occurred more frequently in kar2 and kar8, than in kar5 mutant zygotes. The kinetics of NE fusion in prm3, kar5, and kar8 mutants, measured by live-cell fluorescence microscopy, were well correlated with the size and frequency of bridges observed by ET. However the kar2 mutant was defective for transfer of NE lumenal GFP, but not diffusion within the lumen, suggesting that transfer was blocked at the NE fusion junction. These observations suggest that Prm3p acts before initiation of outer NE fusion, Kar5p may help dilation of the initial fusion pore, and Kar2p and Kar8p act after outer NE fusion, during inner NE fusion.
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the two forms of Karyogamy transcription factor kar4p are regulated by differential initiation of transcription translation and protein turnover
Molecular and Cellular Biology, 1999Co-Authors: Alison E Gammie, Bruce G Stewart, Charles F Scott, Mark D RoseAbstract:Kar4p is a transcription factor in Saccharomyces cerevisiae that is required for the expression of Karyogamy-specific genes during mating, for the efficient transit from G1 during mitosis, and for essential functions during meiosis. Kar4p exists in two forms: a constitutive slower-migrating form, which predominates during vegetative growth, and a faster-migrating form, which is highly induced by mating pheromone. Transcript mapping of KAR4 revealed that the constitutive mRNA was initiated upstream of two in-frame ATG initiation codons, while the major inducible mRNA originated between them. Thus, the two forms of Kar4p are derived from the translation of alternative transcripts, which possess different AUG initiation codons. Site-directed mutations were constructed to inactivate one or the other of the initiation codons, allowing the expression of the two Kar4p forms separately. At normal levels of expression, the constitutive form of Kar4p did not support wild-type levels of mating. However, the two forms of Kar4p could also be expressed separately from the regulatable GAL1 promoter, and no functional difference was detected when they were expressed at equivalent levels. Pulse-chase experiments showed that the induced form of Kar4p was highly expressed and stable during mating but rapidly turned over in vegetative cells. In contrast, the constitutively expressed longer form showed the same rate of turnover regardless of the growth condition. Furthermore, overexpression of either form of Kar4p in vegetative cells was toxic. Thus, the elaborate regulation of the two forms of Kar4p at the levels of transcription, translation, and protein turnover reflects the requirement for high levels of the protein during mating and for low levels during the subsequent phases of the cell cycle.
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kar9p is a novel cortical protein required for cytoplasmic microtubule orientation in yeast
Journal of Cell Biology, 1998Co-Authors: Rita K Miller, Mark D RoseAbstract:kar9 was originally identified as a bilateral Karyogamy mutant, in which the two zygotic nuclei remained widely separated and the cytoplasmic microtubules were misoriented (Kurihara, L.J., C.T. Beh, M. Latterich, R. Schekman, and M.D. Rose. 1994. J. Cell Biol. 126:911–923.). We now report a general defect in nuclear migration and microtubule orientation in kar9 mutants. KAR9 encodes a novel 74-kD protein that is not essential for life. The kar9 mitotic defect was similar to mutations in dhc1 / dyn1 (dynein heavy chain gene), jnm1 , and act5. kar9Δ dhc1Δ , kar9Δ jnm1Δ , and kar9Δ act5Δ double mutants were synthetically lethal, suggesting that these genes function in partially redundant pathways to carry out nuclear migration. A functional GFP-Kar9p fusion protein localized to a single dot at the tip of the shmoo projection. In mitotic cells, GFP-Kar9p localized to a cortical dot with both mother–daughter asymmetry and cell cycle dependence. In small-budded cells through anaphase, GFP-Kar9p was found at the tip of the growing bud. In telophase and G1 unbudded cells, no localization was observed. By indirect immunofluorescence, cytoplasmic microtubules intersected the GFP-Kar9p dot. Nocodazole experiments demonstrated that Kar9p's cortical localization was microtubule independent. We propose that Kar9p is a component of a cortical adaptor complex that orients cytoplasmic microtubules.
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kar4p a Karyogamy specific component of the yeast pheromone response pathway
Molecular and Cellular Biology, 1996Co-Authors: L J Kurihara, B G Stewart, Alison E Gammie, Mark D RoseAbstract:Karyogamy is the process whereby two haploid nuclei fuse to form a diploid nucleus during mating in Saccharomyces cerevisiae. Here, we describe the characterization of the KAR4 gene, previously identified in a screen for new nuclear fusion-defective mutants. During mating, kar4 mutants were defective for the microtubule-dependent movement of nuclei, a phenotype identical to that of mutations in KAR3 and CIK1. Consistent with its mutant phenotype, we found that the kar4 mutation resulted in failure to induce KAR3 and CIK1 mRNA during mating. Expression of KAR3 and CIK1 under independent regulatory control suppressed the kar4 defect, indicating that KAR4 is required primarily for the induction of KAR3 and CIK1. KAR4 was also required for meiosis, during which it may regulate KAR3; however, mitotic expression of KAR3 and CIK1 during S/G2 phase was independent of KAR4. A 30-bp region upstream of KAR3 conferred both KAR4- and STE12-dependent induction by mating pheromone. This region contained one moderate and two weak matches to the consensus pheromone response element to which the Ste12p transcriptional activator binds and five repeats of the sequence CAAA(A). Overproduction of Ste12p suppressed the kar4 defect in KAR3 induction and nuclear fusion. In contrast, Ste12p-independent expression of Kar4p did not alleviate the requirement for Ste12p during KAR3 induction. We propose that Kar4p assists Ste12p in the pheromone-dependent expression of KAR3 and CIK1. KAR4 defines a novel level of regulation for the pheromone response pathway, acting at a subset of Stel2p-inducible genes required for Karyogamy.
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nuclear congression and membrane fusion two distinct events in the yeast Karyogamy pathway
Journal of Cell Biology, 1994Co-Authors: Laurie Jo Kurihara, Martin Latterich, Randy Schekman, Christopher T Beh, Mark D RoseAbstract:Karyogamy is the process where haploid nuclei fuse to form a diploid nucleus during yeast mating. We devised a novel genetic screen that identified five new Karyogamy (KAR) genes and three new cell fusion (FUS) genes. The kar mutants fell into two classes that represent distinct events in the yeast Karyogamy pathway. Class I mutations blocked congression of the nuclei due to cytoplasmic microtubule defects. In Class II mutants, nuclear congression proceeded and the membranes of apposed nuclei were closely aligned but unfused. In vitro, Class II mutant membranes were defective in a homotypic ER/nuclear membrane fusion assay. We propose that Class II mutants define components of a novel membrane fusion complex which functions during vegetative growth and is recruited for Karyogamy.
