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Ikenaga J, Kajihara H, Yoshida M. Kulikovia alborostrata and Kulikovia fulva comb. nov. (Nemertea: Heteronemertea) are Sister Species with Prezygotic Isolating Barriers. Zoolog Sci 2021; 38:193-202. [PMID: 33812359 DOI: 10.2108/zs200112] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 10/13/2020] [Indexed: 11/17/2022]
Abstract
The heteronemertean Kulikovia alborostrata (Takakura, 1898) was originally described as Lineus alborostratus based on material from Misaki, Japan. Although this species was regarded as consisting of two color variants, purple and brown-yellow, the identity of these variants has never been examined based on topotypes. In this study, we performed a multi-locus phylogeny reconstruction, species delimitation analyses, and cross-fertilization experiments to examine the species status of Takakura's original taxon concept consisting of these color variants. Our results suggest that the purple type is identical to Lineus alborostratus Takakura, 1898 auct. (currently Kulikovia alborostrata), whereas the brown-yellow type is conspecific with Lineus fulvus Iwata, 1954, originally established from Hokkaido. These two species appear to have a sister-taxon relationship and are reproductively isolated from each other by prezygotic mechanisms involving gamete incompatibility, minimally separated with 2.8% (16S rRNA) and 14.4% (COI) uncorrected p-distances. We propose that the purple type be considered as representing the true identity of the nominal species Lineus alborostratus (currently assigned to the genus Kulikovia) to maintain the common usage of the name. Although Takakura's type material is not extant, we consider that neotypification is unnecessary in this case because no taxonomic/nomenclatural confusion persists. We also propose to transfer Lineus fulvus to yield Kulikovia fulva comb. nov.
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Affiliation(s)
- Jumpei Ikenaga
- Misaki Marine Biological Station, School of Science, The University of Tokyo, Misaki, Miura, Kanagawa 238-0225, Japan
| | - Hiroshi Kajihara
- Faculty of Science, Hokkaido University, Sapporo, Hokkaido 060-0180, Japan
| | - Manabu Yoshida
- Misaki Marine Biological Station, School of Science, The University of Tokyo, Misaki, Miura, Kanagawa 238-0225, Japan,
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Limatola N, Chun JT, Santella L. Effects of Salinity and pH of Seawater on the Reproduction of the Sea Urchin Paracentrotus lividus. THE BIOLOGICAL BULLETIN 2020; 239:13-23. [PMID: 32812816 DOI: 10.1086/710126] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
AbstractFertilization and early development are usually the most vulnerable stages in the life of marine animals, and the biological processes during this period are highly sensitive to the environment. In nature, sea urchin gametes are shed in seawater, where they undergo external fertilization and embryonic development. In a laboratory, it is possible to follow the exact morphological and biochemical changes taking place in the fertilized eggs and the developing embryos. Thus, observation of successful fertilization and the subsequent embryonic development of sea urchin eggs can be used as a convenient biosensor to assess the quality of the marine environment. In this paper, we have examined how salinity and pH changes affect the normal fertilization process and the following development of Paracentrotus lividus. The results of our studies using confocal microscopy, scanning and transmission electron microscopy, and time-lapse Ca2+ image recording indicated that both dilution and acidification of seawater have subtle but detrimental effects on many aspects of the fertilization process. They include Ca2+ signaling and coordinated actin cytoskeletal changes, leading to a significantly reduced rate of successful fertilization and, eventually, to abnormal or delayed embryonic development.
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Polyspermy-preventing mechanisms in sea urchin eggs: New developments for an old problem. Biochem Biophys Res Commun 2019; 520:695-698. [DOI: 10.1016/j.bbrc.2019.10.024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 10/01/2019] [Indexed: 12/21/2022]
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Espinoza-Fonseca LM. The Ca 2+-ATPase pump facilitates bidirectional proton transport across the sarco/endoplasmic reticulum. MOLECULAR BIOSYSTEMS 2017; 13:633-637. [PMID: 28290590 DOI: 10.1039/c7mb00065k] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Ca2+ transport across the sarco/endoplasmic reticulum (SR) plays an essential role in intracellular Ca2+ homeostasis, signalling, cell differentiation and muscle contractility. During SR Ca2+ uptake and release, proton fluxes are required to balance the charge deficit generated by the exchange of Ca2+ and other ions across the SR. During Ca2+ uptake by the SR Ca2+-ATPase (SERCA), two protons are countertransported from the SR lumen to the cytosol, thus partially compensating for the charge moved by Ca2+ transport. Studies have shown that protons are also transported from the cytosol to the lumen during Ca2+ release, but a transporter that facilitates proton transport into the SR lumen has not been described. In this article we propose that SERCA forms pores that facilitate bidirectional proton transport across the SR. We describe the location and structure of water-filled pores in SERCA that form cytosolic and luminal pathways for protons to cross the SR membrane. Based on this structural information, we suggest mechanistic models for proton translocation to the cytosol during active Ca2+ transport, and into the SR lumen during SERCA inhibition by endogenous regulatory proteins. Finally, we discuss the physiological consequences of SERCA-mediated bidirectional proton transport across the SR membrane of muscle and non-muscle cells.
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Affiliation(s)
- L Michel Espinoza-Fonseca
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA.
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Fernández-de Gortari E, Espinoza-Fonseca LM. Preexisting domain motions underlie protonation-dependent structural transitions of the P-type Ca 2+-ATPase. Phys Chem Chem Phys 2017; 19:10153-10162. [PMID: 28374038 PMCID: PMC5472844 DOI: 10.1039/c7cp00243b] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We have performed microsecond molecular dynamics (MD) simulations to determine the mechanism for protonation-dependent structural transitions of the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA), one of the most prominent members of the large P-type ATPase superfamily that transports ions across biological membranes. The release of two H+ from the transport sites activates SERCA by inducing a structural transition between low (E2) and high (E1) Ca2+-affinity states (E2-to-E1 transition), but the structural mechanism by which transport site deprotonation facilitates this transition is unknown. We performed microsecond all-atom MD simulations to determine the effects of transport site protonation on the structural dynamics of the E2 state in solution. We found that the protonated E2 state has structural characteristics that are similar to those observed in crystal structures of E2. Upon deprotonation, a single Na+ ion rapidly (<10 ns) binds to the transmembrane transport sites and induces a kink in M5, disrupts the M3-M5 interface, and increases the mobility of the M3/A-M3 linker. Principal component analysis showed that counter-rotation of the cytosolic N-A domains about the membrane normal axis, which is the primary motion driving the E2-to-E1 transition, is present in both protonated and deprotonated E2 states; however, protonation-dependent structural changes in the transmembrane domain control the hierarchical organization and amplitude of this motion. We propose that preexisting rigid-body domain motions underlie structural transitions of SERCA, where the functionally important directionality is preserved while transport site protonation controls the dominance and amplitude of motion to shift the equilibrium between the E1 and E2 states. We conclude that ligand-induced modulation of preexisting domain motions is likely a common theme in structural transitions of the P-type ATPase superfamily.
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Affiliation(s)
- Eli Fernández-de Gortari
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA.
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Takayama J, Onami S. The Sperm TRP-3 Channel Mediates the Onset of a Ca 2+ Wave in the Fertilized C. elegans Oocyte. Cell Rep 2016; 15:625-637. [DOI: 10.1016/j.celrep.2016.03.040] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 02/02/2016] [Accepted: 03/10/2016] [Indexed: 11/17/2022] Open
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Stricker SA, Beckstrom B, Mendoza C, Stanislawski E, Wodajo T. Oocyte aging in a marine protostome worm: The roles of maturation-promoting factor and extracellular signal regulated kinase form of mitogen-activated protein kinase. Dev Growth Differ 2016; 58:250-9. [PMID: 26918273 DOI: 10.1111/dgd.12269] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 12/29/2015] [Accepted: 01/10/2016] [Indexed: 12/15/2022]
Abstract
The roles of maturation-promoting factor (MPF) and an extracellular signal regulated kinase form of mitogen-activated protein kinase (ERK MAPK) are analyzed during oocyte aging in the marine protostome worm Cerebratulus. About a day after removal from the ovary, unfertilized metaphase-I-arrested oocytes of Cerebratulus begin to flatten and swell before eventually lysing, thereby exhibiting characteristics of a necroptotic mode of regulated cell death. Based on immunoblots probed with phospho-specific antibodies, MPF and ERK are initially active in freshly mature specimens. However, as oocytes age, both kinase activities decline, with ERK deactivation occurring well before MPF downregulation. Experiments using pharmacological modulators indicate that oocyte degradation is promoted by the maturation-initiated activation of ERK as well as by the deactivation of MPF that occurs in extensively aged specimens. The potential significance of these findings is discussed relative to previously published results for apoptotic eggs and oocytes of echinoderm and vertebrate deuterostomes.
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Affiliation(s)
- Stephen A Stricker
- Department of Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM, 87131, USA
| | - Bradley Beckstrom
- Department of Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM, 87131, USA
| | - Cristina Mendoza
- Department of Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM, 87131, USA
| | - Emma Stanislawski
- Department of Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM, 87131, USA
| | - Tewodros Wodajo
- Department of Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM, 87131, USA
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Santella L, Limatola N, Chun JT. Calcium and actin in the saga of awakening oocytes. Biochem Biophys Res Commun 2015; 460:104-13. [PMID: 25998739 DOI: 10.1016/j.bbrc.2015.03.028] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 03/06/2015] [Indexed: 12/12/2022]
Abstract
The interaction of the spermatozoon with the egg at fertilization remains one of the most fascinating mysteries of life. Much of our scientific knowledge on fertilization comes from studies on sea urchin and starfish, which provide plenty of gametes. Large and transparent, these eggs have served as excellent model systems for studying egg activation and embryo development in seawater, a plain natural medium. Starfish oocytes allow the study of the cortical, cytoplasmic and nuclear changes during the meiotic maturation process, which can also be triggered in vitro by hormonal stimulation. These morphological and biochemical changes ensure successful fertilization of the eggs at the first metaphase. On the other hand, sea urchin eggs are fertilized after the completion of meiosis, and are particularly suitable for the study of sperm-egg interaction, early events of egg activation, and embryonic development, as a large number of mature eggs can be fertilized synchronously. Starfish and sea urchin eggs undergo abrupt changes in the cytoskeleton and ion fluxes in response to the fertilizing spermatozoon. The plasma membrane and cortex of an egg thus represent "excitable media" that quickly respond to the stimulus with the Ca(2+) swings and structural changes. In this article, we review some of the key findings on the rapid dynamic rearrangements of the actin cytoskeleton in the oocyte/egg cortex upon hormonal or sperm stimulation and their roles in the modulation of the Ca(2+) signals and in the control of monospermic fertilization.
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Affiliation(s)
- Luigia Santella
- Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Villa Comunale 1, Napoli, I-80121, Italy.
| | - Nunzia Limatola
- Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Villa Comunale 1, Napoli, I-80121, Italy
| | - Jong T Chun
- Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Villa Comunale 1, Napoli, I-80121, Italy
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