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Tatsuya Togashi - One of the best experts on this subject based on the ideXlab platform.
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Within-clutch variability in Gamete size arises from the size variation in gametangia in the marine green alga Monostroma angicava
Plant Reproduction, 2018Co-Authors: Yusuke Horinouchi, Tatsuya TogashiAbstract:Key message Within-clutch Gamete size variability in Monostroma angicava. Abstract In many organisms, it is unclear how the size variation in Gametes is generated in each clutch (i.e., total Gametes produced by a gametophyte for a single spawning) or how Gamete size is adjusted. Within-clutch variation in Gamete size has been explained as a result of either physiological/developmental constraints or bet hedging during gametogenesis. These two explanations have been assumed to be mutually exclusive, and related observations are conflicting. The slightly anisogamous dioecious green alga Monostroma angicava employs a simple mechanism to produce Gametes of each sex: each vegetative cell becomes a single gametangium cell, which synchronously divides to form equally sized Gametes. The number of such cell divisions has several variations, which might vary Gamete size. We measured the volume of gametangia in each clutch, counted the number of cell divisions in each gametangium and estimated the size of the Gametes. We found that larger gametangia divided more times than smaller gametangia in both sexes, although male gametangia were smaller than female gametangia when they underwent the same number of cell divisions. Therefore, the variation in the number of cell divisions during gametogenesis serves to adjust Gamete size in each sex rather than to vary it. Within-clutch Gamete size variability originates in within-clutch variation in gametangium size: any factors that increase the variation in the size of gametangia can increase the within-clutch variation in Gamete size.
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within clutch variability in Gamete size arises from the size variation in gametangia in the marine green alga monostroma angicava
Sexual Plant Reproduction, 2018Co-Authors: Yusuke Horinouchi, Tatsuya TogashiAbstract:Within-clutch Gamete size variability in Monostroma angicava. In many organisms, it is unclear how the size variation in Gametes is generated in each clutch (i.e., total Gametes produced by a gametophyte for a single spawning) or how Gamete size is adjusted. Within-clutch variation in Gamete size has been explained as a result of either physiological/developmental constraints or bet hedging during gametogenesis. These two explanations have been assumed to be mutually exclusive, and related observations are conflicting. The slightly anisogamous dioecious green alga Monostroma angicava employs a simple mechanism to produce Gametes of each sex: each vegetative cell becomes a single gametangium cell, which synchronously divides to form equally sized Gametes. The number of such cell divisions has several variations, which might vary Gamete size. We measured the volume of gametangia in each clutch, counted the number of cell divisions in each gametangium and estimated the size of the Gametes. We found that larger gametangia divided more times than smaller gametangia in both sexes, although male gametangia were smaller than female gametangia when they underwent the same number of cell divisions. Therefore, the variation in the number of cell divisions during gametogenesis serves to adjust Gamete size in each sex rather than to vary it. Within-clutch Gamete size variability originates in within-clutch variation in gametangium size: any factors that increase the variation in the size of gametangia can increase the within-clutch variation in Gamete size.
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evolutionary trajectories explain the diversified evolution of isogamy and anisogamy in marine green algae
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Tatsuya Togashi, John L Bartelt, Jin Yoshimura, Kei-ichi TainakaAbstract:The evolution of anisogamy (the production of Gametes of different size) is the first step in the establishment of sexual dimorphism, and it is a fundamental phenomenon underlying sexual selection. It is believed that anisogamy originated from isogamy (production of Gametes of equal size), which is considered by most theorists to be the ancestral condition. Although nearly all plant and animal species are anisogamous, extant species of marine green algae exhibit a diversity of mating systems including both isogamy and anisogamy. Isogamy in marine green algae is of two forms: isogamy with extremely small Gametes and isogamy with larger Gametes. Based on disruptive selection for fertilization success and zygote survival (theory of Parker, Baker, and Smith), we explored how environmental changes can contribute to the evolution of such complex mating systems by analyzing the stochastic process in the invasion simulations of populations of differing Gamete sizes. We find that both forms of isogamy can evolve from other isogamous ancestors through anisogamy. The resulting dimensionless analysis accounts for the evolutionary stability of all types of mating systems in marine green algae, even in the same environment. These results imply that evolutionary trajectories as well as the optimality of Gametes/zygotes played an important role in the evolution of Gamete size.
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Effects of Gamete behavior and density on fertilization success in marine green algae: insights from three-dimensional numerical simulations
Aquatic Ecology, 2008Co-Authors: Tatsuya Togashi, Kei-ichi Tainaka, Jin Yoshimura, Masaru Nagisa, Tatsuo Miyazaki, John L BarteltAbstract:We developed a numerical simulation of mating experiment to study effects of phototactic Gamete behavior and density on fertilization success, using the C++ programming language, and pseudo-parallelization methods with input parameters based on experimental data. In our experiments, we found that Gametes with positive phototaxis are favored, particularly in shallow water, because they can search for potential mates on the two-dimensional (2-D) water surface rather than randomly in three dimensions. We also found evidence that sperm (male Gametes) limitation might not be the dominant selective force in the evolution of isogamous or slightly anisogamous marine green algae because almost all of female Gametes can be fertilized on the 2-D water surface meaning they might not be under sperm limited conditions. Gamete density also appears to affect mating success seriously. These findings were produced by some technical progress made recently to rapidly and correctly count the numbers of zygotes formed calculating the locations of huge numbers of male and female Gametes in the test tank. Both Gamete behavior and density might be determined by environmental conditions of habitat, particularly the depth of water.
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Simulation of Gamete behaviors and the evolution of anisogamy: reproductive strategies of marine green algae
Ecological Research, 2004Co-Authors: Tatsuya Togashi, John L BarteltAbstract:In marine green algae, isogamous or slightly anisogamous species are taxonomically widespread. They produce positively phototactic Gametes in both sexes. We developed a new numerical simulator of Gamete behavior using C++ and pseudo-parallelization methods to elucidate potential advantages of phototaxis. Input parameters were set based on experimental data. Each Gamete swimming in a virtual rectangular test tank was tracked and the distances between the centers of nearby male and female were measured at each step to detect collisions. Our results shed light on the roles of Gamete behavior and the mechanisms of the evolution of anisogamy and more derived forms of sexual dimorphism. We demonstrated that not only Gametes with positive phototaxis were favored over those without, particularly in shallow water. This was because they could search for potential mates on the 2-D water surface rather than randomly in three dimensions. Also, phototactic behavior clarified the difference between isogamy and slight anisogamy. Isogamous species produced more zygotes than slightly anisogamous ones only under the phototactic conditions. Our results suggested that ‘sperm limitation’ might be easily resolved particularly in the slightly anisogamous species. Some more markedly anisogamous species produce the smaller male Gametes without any phototactic devices and the larger positively phototactic female Gametes. In such species, female Gametes attract their partners using a sexual pheromone. This pheromonal attraction system might have played a key role in the evolution of anisogamy, because it could enable markedly anisogamous species achieve 2-D search efficiencies on the water surface. The mating systems appear to be tightly tuned o the environmental conditions of their habitats.
Taizo Motomura - One of the best experts on this subject based on the ideXlab platform.
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a brown algal sex pheromone reverses the sign of phototaxis by camp ca2 dependent signaling in the male Gametes of mutimo cylindricus cutleriaceae
Journal of Photochemistry and Photobiology B-biology, 2019Co-Authors: Nana Kinoshitaterauchi, Taizo Motomura, Kogiku Shiba, Taiki Umezawa, Fuyuhiko Matsuda, Kazuo InabaAbstract:Abstract Male Gametes of the brown alga Mutimo cylindricus show positive phototaxis soon after spawning in seawater but gradually change the sign of phototaxis with time. This conversion appears to need the decrease of intracellular Ca2+ concentration. In this study, we revealed that the conversion of male Gamete phototactic sign, positive to negative, was accelerated by mixing with female Gametes. The supernatant after the centrifugation of female Gamete suspension showed the same activity to change the phototactic sign, suggesting that a factor released from female Gametes was responsible for the reaction. A known brown algal sex pheromone, ectocarpene, induced chemotaxis of male Gametes of M. cylindricus. The addition of this compound induced the change of phototactic sign, clearly indicating that a sex pheromone is essential for the reversal. An inhibitor of phosphodiesterase, theophylline, inhibited the chemotaxis and phototactic sign reversion by a factor released from female Gametes and ectocarpene. Measurements of cyclic nucleotides showed that the increase in intracellular concentration of cAMP, not cGMP, was parallel to the change of phototactic sign. The inhibition of phototactic sign by theophylline was not observed in low Ca2+ sea water. These results suggest that a signaling pathway mediated by cAMP and Ca2+ concentrations drives the interconversion between two important behaviors of male Gametes, phototaxis and chemotaxis.
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Identification of three proteins involved in fertilization and parthenogenetic development of a brown alga, Scytosiphon lomentaria
Planta, 2014Co-Authors: Tatyana A. Klochkova, Junbo Shim, Chikako Nagasato, Taizo MotomuraAbstract:Metabolic pathways of cell organelles may influence the expression of nuclear genes involved in fertilization and subsequent zygote development through a retrograde regulation. In Scytosiphon lomentaria , inheritance of chloroplast is biparental but mitochondria are maternally inherited. Male and female Gametes underwent different parthenogenetic outcomes. Most (>99 %) male Gametes did not differentiate rhizoid cells or survived beyond four-cell stage, while over 95 % of female Gametes grew into mature asexual plants. Proteomic analysis showed that the protein contents of male and female Gametes differed by approximately 1.7 %, 12 sex-specific proteins out of 700 detected proteins. Three sex-specific proteins were isolated and identified using CAF-MALDI mass spectrometry and RACE-PCR. Among them, a male Gamete-specific homoaconitate hydratase (HACN) and a female Gamete-specific succinate semialdehyde dehydrogenase (SSADH) were predicted to be the genes involved in mitochondrial metabolic pathways. The expression level of both mitochondrial genes was dramatically changed at the fertilization event. During parthenogenetic development the male-specific HACN and GTP-binding protein were gradually down-regulated but SSADH stayed up-regulated up to 48 h. To observe the effect of chemicals on the expression of these genes, male and female Gametes were treated with γ-aminobutyric acid (GABA), hydrogen peroxide and l -ascorbic acid. Among them GABA treatment significantly reduced SSADH gene expression in female Gamete but the same treatment induced high upregulation of the gene in male Gamete. GABA treatment affected the behavior of Gametes and their parthenogenetic development. Both Gametes showed prolonged motile stage, retarded settlement and subsequent parthenogenetic development. Our results suggest that male and female Gametes regulate mitochondrial metabolic pathways differentially during fertilization, which may be the reason for their physiological and behavioral differences.
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gametic behavior in a marine green alga monostroma angicava an effect of phototaxis on mating efficiency
Sexual Plant Reproduction, 1999Co-Authors: Tatsuya Togashi, Taizo Motomura, Terunobu IchimuraAbstract:The role of phototactic behavior of Gametes was tested experimentally in the slightly anisogamous marine green alga Monostroma angicava Kjellman, and the effect of phototaxis on mating efficiency was discovered. Both male and female Gametes showed positive phototaxis in response to a white light source. In contrast, they did not respond to a red light source. Their swimming velocity did not differ between these two illuminating light sources. It was, therefore, suggested that the search ability of the Gamete itself might not vary between phototactic and non-phototactic conditions. The number of zygotes formed during the mating process may be expressed as the product of the number of encounters between male and female Gametes and the fraction of encounters that result in sexual fusion. In this study, with high densities of male and female Gametes mixed in test tubes, almost all minor (fewer in number) Gametes fused sexually within 10 min. After dilution of the Gamete suspensions by half, mating efficiency in test tubes illuminated by white light from above was higher than that in dark controls. This suggests that male and female Gametes gathered at the water surface through their positive phototaxis, thus increasing the rate of encounters. Mating efficiency also decreased if the test tubes were illuminated from above by white light and also shaken. Since negative phototaxis is clearly shown in planozygotes, we suggest that positive phototaxis of male and female Gametes in M. angicava is an adaptive trait for increasing the rate of gametic encounters rather than for the dispersal of zygotes as previously reported for zoospores of some marine algae.
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production of anisoGametes and Gamete motility dimorphism in monostroma angicava
Sexual Plant Reproduction, 1997Co-Authors: Tatsuya Togashi, Taizo Motomura, Terunobu IchimuraAbstract:The reproductive strategy of a marine alga with a heteromorphic biphasic life cycle was studied by analyzing various sexual reproductive characters in light of the evolution of anisogamy. Gametophytes of Monostroma angicava were dioecious and their Gametes were slightly anisogamous. Volume of gametangium, density of gametangia and area of mature gametangial parts on each gametophyte did not differ from male to female. Therefore, the reproductive biomass investment for Gamete production was considered to be the same for each sex. Anisogamy in this alga appeared to be derived from the difference in the number of cell divisions during gametogenesis, because the majority of male gametangia each produced 64 (26) Gametes and the female produced 32 (25) Gametes. This corresponded with measurements of cell size in male and female Gametes. Further, the sex ratio was 1:1 for sexually mature plants sampled at Charatsunai. Therefore, it was suggested that in the field twice as many male Gametes are released as female Gametes. Liberated Gametes of both sexes showed positive phototaxis. The swimming velocity of freshly liberated male Gametes was a little higher than that of female Gametes. Male Gametes had the potential to swim for ca. 72 h and female Gametes for ca. 84 h. The difference in Gamete motility between the two sexes seemed to be related to cell size. Planozygotes were negatively phototactic and swam more rapidly than Gametes of either sex.
Jin Yoshimura - One of the best experts on this subject based on the ideXlab platform.
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evolutionary trajectories explain the diversified evolution of isogamy and anisogamy in marine green algae
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Tatsuya Togashi, John L Bartelt, Jin Yoshimura, Kei-ichi TainakaAbstract:The evolution of anisogamy (the production of Gametes of different size) is the first step in the establishment of sexual dimorphism, and it is a fundamental phenomenon underlying sexual selection. It is believed that anisogamy originated from isogamy (production of Gametes of equal size), which is considered by most theorists to be the ancestral condition. Although nearly all plant and animal species are anisogamous, extant species of marine green algae exhibit a diversity of mating systems including both isogamy and anisogamy. Isogamy in marine green algae is of two forms: isogamy with extremely small Gametes and isogamy with larger Gametes. Based on disruptive selection for fertilization success and zygote survival (theory of Parker, Baker, and Smith), we explored how environmental changes can contribute to the evolution of such complex mating systems by analyzing the stochastic process in the invasion simulations of populations of differing Gamete sizes. We find that both forms of isogamy can evolve from other isogamous ancestors through anisogamy. The resulting dimensionless analysis accounts for the evolutionary stability of all types of mating systems in marine green algae, even in the same environment. These results imply that evolutionary trajectories as well as the optimality of Gametes/zygotes played an important role in the evolution of Gamete size.
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Effects of Gamete behavior and density on fertilization success in marine green algae: insights from three-dimensional numerical simulations
Aquatic Ecology, 2008Co-Authors: Tatsuya Togashi, Kei-ichi Tainaka, Jin Yoshimura, Masaru Nagisa, Tatsuo Miyazaki, John L BarteltAbstract:We developed a numerical simulation of mating experiment to study effects of phototactic Gamete behavior and density on fertilization success, using the C++ programming language, and pseudo-parallelization methods with input parameters based on experimental data. In our experiments, we found that Gametes with positive phototaxis are favored, particularly in shallow water, because they can search for potential mates on the two-dimensional (2-D) water surface rather than randomly in three dimensions. We also found evidence that sperm (male Gametes) limitation might not be the dominant selective force in the evolution of isogamous or slightly anisogamous marine green algae because almost all of female Gametes can be fertilized on the 2-D water surface meaning they might not be under sperm limited conditions. Gamete density also appears to affect mating success seriously. These findings were produced by some technical progress made recently to rapidly and correctly count the numbers of zygotes formed calculating the locations of huge numbers of male and female Gametes in the test tank. Both Gamete behavior and density might be determined by environmental conditions of habitat, particularly the depth of water.
Kei-ichi Tainaka - One of the best experts on this subject based on the ideXlab platform.
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evolutionary trajectories explain the diversified evolution of isogamy and anisogamy in marine green algae
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Tatsuya Togashi, John L Bartelt, Jin Yoshimura, Kei-ichi TainakaAbstract:The evolution of anisogamy (the production of Gametes of different size) is the first step in the establishment of sexual dimorphism, and it is a fundamental phenomenon underlying sexual selection. It is believed that anisogamy originated from isogamy (production of Gametes of equal size), which is considered by most theorists to be the ancestral condition. Although nearly all plant and animal species are anisogamous, extant species of marine green algae exhibit a diversity of mating systems including both isogamy and anisogamy. Isogamy in marine green algae is of two forms: isogamy with extremely small Gametes and isogamy with larger Gametes. Based on disruptive selection for fertilization success and zygote survival (theory of Parker, Baker, and Smith), we explored how environmental changes can contribute to the evolution of such complex mating systems by analyzing the stochastic process in the invasion simulations of populations of differing Gamete sizes. We find that both forms of isogamy can evolve from other isogamous ancestors through anisogamy. The resulting dimensionless analysis accounts for the evolutionary stability of all types of mating systems in marine green algae, even in the same environment. These results imply that evolutionary trajectories as well as the optimality of Gametes/zygotes played an important role in the evolution of Gamete size.
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Effects of Gamete behavior and density on fertilization success in marine green algae: insights from three-dimensional numerical simulations
Aquatic Ecology, 2008Co-Authors: Tatsuya Togashi, Kei-ichi Tainaka, Jin Yoshimura, Masaru Nagisa, Tatsuo Miyazaki, John L BarteltAbstract:We developed a numerical simulation of mating experiment to study effects of phototactic Gamete behavior and density on fertilization success, using the C++ programming language, and pseudo-parallelization methods with input parameters based on experimental data. In our experiments, we found that Gametes with positive phototaxis are favored, particularly in shallow water, because they can search for potential mates on the two-dimensional (2-D) water surface rather than randomly in three dimensions. We also found evidence that sperm (male Gametes) limitation might not be the dominant selective force in the evolution of isogamous or slightly anisogamous marine green algae because almost all of female Gametes can be fertilized on the 2-D water surface meaning they might not be under sperm limited conditions. Gamete density also appears to affect mating success seriously. These findings were produced by some technical progress made recently to rapidly and correctly count the numbers of zygotes formed calculating the locations of huge numbers of male and female Gametes in the test tank. Both Gamete behavior and density might be determined by environmental conditions of habitat, particularly the depth of water.
Yusuke Horinouchi - One of the best experts on this subject based on the ideXlab platform.
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Within-clutch variability in Gamete size arises from the size variation in gametangia in the marine green alga Monostroma angicava
Plant Reproduction, 2018Co-Authors: Yusuke Horinouchi, Tatsuya TogashiAbstract:Key message Within-clutch Gamete size variability in Monostroma angicava. Abstract In many organisms, it is unclear how the size variation in Gametes is generated in each clutch (i.e., total Gametes produced by a gametophyte for a single spawning) or how Gamete size is adjusted. Within-clutch variation in Gamete size has been explained as a result of either physiological/developmental constraints or bet hedging during gametogenesis. These two explanations have been assumed to be mutually exclusive, and related observations are conflicting. The slightly anisogamous dioecious green alga Monostroma angicava employs a simple mechanism to produce Gametes of each sex: each vegetative cell becomes a single gametangium cell, which synchronously divides to form equally sized Gametes. The number of such cell divisions has several variations, which might vary Gamete size. We measured the volume of gametangia in each clutch, counted the number of cell divisions in each gametangium and estimated the size of the Gametes. We found that larger gametangia divided more times than smaller gametangia in both sexes, although male gametangia were smaller than female gametangia when they underwent the same number of cell divisions. Therefore, the variation in the number of cell divisions during gametogenesis serves to adjust Gamete size in each sex rather than to vary it. Within-clutch Gamete size variability originates in within-clutch variation in gametangium size: any factors that increase the variation in the size of gametangia can increase the within-clutch variation in Gamete size.
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within clutch variability in Gamete size arises from the size variation in gametangia in the marine green alga monostroma angicava
Sexual Plant Reproduction, 2018Co-Authors: Yusuke Horinouchi, Tatsuya TogashiAbstract:Within-clutch Gamete size variability in Monostroma angicava. In many organisms, it is unclear how the size variation in Gametes is generated in each clutch (i.e., total Gametes produced by a gametophyte for a single spawning) or how Gamete size is adjusted. Within-clutch variation in Gamete size has been explained as a result of either physiological/developmental constraints or bet hedging during gametogenesis. These two explanations have been assumed to be mutually exclusive, and related observations are conflicting. The slightly anisogamous dioecious green alga Monostroma angicava employs a simple mechanism to produce Gametes of each sex: each vegetative cell becomes a single gametangium cell, which synchronously divides to form equally sized Gametes. The number of such cell divisions has several variations, which might vary Gamete size. We measured the volume of gametangia in each clutch, counted the number of cell divisions in each gametangium and estimated the size of the Gametes. We found that larger gametangia divided more times than smaller gametangia in both sexes, although male gametangia were smaller than female gametangia when they underwent the same number of cell divisions. Therefore, the variation in the number of cell divisions during gametogenesis serves to adjust Gamete size in each sex rather than to vary it. Within-clutch Gamete size variability originates in within-clutch variation in gametangium size: any factors that increase the variation in the size of gametangia can increase the within-clutch variation in Gamete size.
