Behavior of flagella and flagellar root systems in the planozygotes and settled zygotes of the green alga Bryopsis maxima Okamura (Ulvophyceae,Chlorophyta) with reference to spatial arrangement of eyespot and cell fusion site

Behaviors of male and female gametes, planozygotes and their microtubular cytoskeletons of a marine green alga Bryopsis maxima Okamura were studied using field emission scanning electron microscopy, high‐speed video microscopy, and anti‐tubulin immunofluorescence microscopy. After fusion of the biflagellate male and female gametes, two sets of basal bodies lay side by side in the planozygote. Four long female microtubular roots extended from the basal bodies to the cell posterior. Four short male roots extended to nearly half the distance to the posterior end. Two flagella, one each from the male and female gametes, become a pair. Specifically, the no. 2 flagellum of the female gamete and one male flagellum point to the right side of the eyespot of the female gamete, which is located at the cell posterior and which is associated with 2s and 2d roots of the female gamete. This spatial relationship of the flagella, microtubular roots, and the eyespot in the planozygote is retained until settlement. During forward swimming, the planozygote swings the flagella backward and moves by flagellar beating. The male and female flagella in the pair usually beat synchronously. The cell withdraws the flagella and becomes round when the planozygote settles to the substratum 20 min after mixing. The axoneme and microtubular roots depolymerize, except for the proximal part and the basal bodies. Subsequently, distinct arrays of cortical microtubules develop in zygotes until 30 min after mixing. These results are discussed with respect to the functional significance of the spatial relationships of flagellar apparatus‐eyespot‐cell fusion sites in the mating gametes and planozygote of green algae.     

我国被子植物体外受精研究—十年回顾

简要回顾了十余年来我国被子植物体外受精领域的研究历程和主要成就。我国科学家在性细胞的分离 ,尤其是生活胚囊和雌配子的分离方面走在国际前列。在一定程度上我国科学家的开拓性工作引起了国际同行的广泛兴趣和重视 ,推动了该领域的迅速发展 ,为实现被子植物真正意义的体外受精做出了独特的贡献。十年来 ,我国已建立了自己独特的被子植物离体受精实验技术系统并利用该系统与国际同行合作进行了一系列研究 ,尤其在探讨配子相互作用、卵细胞激活、避免多精入卵的机制等方面做出了创新性工作 ,为正确认识体外受精系统的优越性与局限性 ,也为深入探讨受精机制提供了有价值的新资料。目前正以体外受精操作系统结合细胞生物学和分子生物学等多种手段对受精过程中的一些重要事态与机理做进一步探讨     

Making muslim babies: Ivf and gamete donation in sunni versus shi’a islam

Medical anthropological research on science, biotechnology, and religion has focused on the “local moral worlds” of men and women as they make difficult decisions regarding their health and the beginnings and endings of human life. This paper focuses on the local moral worlds of infertile Muslims as they attempt to make, in the religiously correct fashion, Muslim babies at in vitro fertilization (IVF) clinics in Egypt and Lebanon. As early as 1980, authoritative fatwas issued from Egypt’s famed Al-Azhar University suggested that IVF and similar technologies are permissible as long as they do not involve any form of third-party donation (of sperm, eggs, embryos, or uteruses). Since the late 1990s, however, divergences in opinion over third-party gamete donation have occurred between Sunni and Shi’ite Muslims, with Iran’s leading ayatollah permitting gamete donation under certain conditions. This Iranian fatwa has had profound implications for the country of Lebanon, where a Shi’ite majority also seeks IVF services. Based on three periods of ethnographic research in Egyptian and Lebanese IVF clinics, this paper explores official and unofficial religious discourses surrounding the practice of IVF and third-party donation in the Muslim world, as well as the gender implications of gamete donation for Muslim marriages.     

Why Gametes are not Like Enriched Uranium

According to Rivka Weinberg, gametes are like enriched uranium: both are hazardous materials. Exposing human beings to enriched uranium can result in radioactivity and decreased life expectancy, while exposing sperm and ova to each other can result in the creation of needy innocent persons with full moral status. Weinberg argues that when we engage in activities that put our gametes at risk of joining with others and growing into persons, we assume the costs of that risky activity. She calls this the Hazmat Theory of parental responsibility. The theory is novel and important, and has far‐reaching consequences for the ethics of procreation, parenting, and population, implying among other things that that the only way to avoid acquiring parental responsibilities may be to “abstain from sexual intercourse or surgically interfere with our gamete‐release system.” For these reasons the theory merits careful scrutiny. In this article I criticize the theory's account of how parental responsibility is acquired and its treatment of the standard of care expected of gamete possessors, and argue that it fails to properly account for a distinction between procreative costs and parental responsibility. Even if gametes are hazardous, it does not follow that parental responsibility in Weinberg's sense is acquired whenever one brings new persons into existence.     

ION FLUXES AND MODIFICATION OF THE EXTRACELLULAR MATRIX DURING GAMETE RELEASE IN FUCOID ALGAE

A rapid phase transition in the extracellular matrix (ECM) of the reproductive tissues (= receptacles) has been proposed to cause gamete release in fucoid algae. We tested this model with cryoanalytical energy dispersive x-ray microanalysis (EDX) scanning electron microscopy (SEM) of rapidly frozen hydrated receptacles of Silvetia compressa Serrão, Cho, Boo et Brawley that were planed to smooth faces using a cryoultramicrotome. Every receptacle typically contained a region(s) of intracellular accumulation of K and Cl and a region(s) of efflux of K and Cl to the ECMs, regardless of treatment (e.g. calm vs. shaken conditions in the light, anthracene-9-carboxylic acid). Although longitudinal variations in [K] and [Cl] between ECM and cells were common, a tissue within any transverse plane of the receptacle was in the same state of efflux or accumulation of K and Cl. The strongest and most extensive effluxes occurred during the time of irreversible commitment to gamete release (i.e. 2–4 min darkness after light potentiation). A receptacle may oscillate rapidly between global states of accumulation and efflux at this time. The polysaccharide collar between the oogonium and stalk cell expanded during Cl and K efflux into the ECM of the conceptacle and condensed when [K] and [Cl] were low in the conceptacle ECM. During periods of strong efflux associated with gamete release, the collar and other components of the exochiton ruptured. Detached gametangia were guided to the pore by the paraphyses. The ECM of the conceptacle is sulfur rich (226 mM) compared with the ECM of the medulla (8 mM). This analysis supports the importance of osmotic modification of the ECM during gamete release and demonstrates that the receptacle is a dynamic signaling organ.     

An alpha-L-fucosidase potentially involved in fertilization is present on Drosophila spermatozoa surface

Drosophila is emerging as a model organism to investigate egg fertilization in insects and the possible conservation of molecular mechanisms of gamete interactions demonstrated in higher organisms. This study shows that the spermatozoa of several species of Drosophila belonging to the melanogaster group have a plasma membrane associated alpha-L-fucosidase with features in common with alpha-L-fucosidases from sperm of other animals, including mammals. The enzyme has been purified and completely characterized in D. ananassae, because of its stability in this species. The sperm alpha-L-fucosidase is an integral protein terminally mannosylated, with the catalytic site oriented toward the extracellular space. It has a M(r) of 256 kDa and a multimeric structure made up by subunits of 48 and 55 kDa. Enzyme characterization included kinetic properties, pI, optimal pH, and thermal stability. A soluble form of the enzyme similar to the sperm associated alpha-L-fucosidase is secreted by the seminal vesicles. Synthetic peptides designed from the deduced product of the D. melanogaster gene encoding an alpha-L-fucosidase were used to raise a specific polyclonal antibody. Immunofluorescence labeling of spermatozoa showed that the enzyme is present in the sperm plasma membrane overlying the acrosome and the tail. Lectin cytochemistry analysis of the egg surface indicated that alpha-L-fucose terminal residues are present on the chorion with a strongly polarized localization on the micropyle. The alpha-L-fucosidase of Drosophila sperm plasma membrane appears to be potentially involved in gamete recognition by interacting with its glycoside ligands present on the egg surface at the site of sperm entry.     

Hologenomic speciation: synergy between a male‐killing bacterium and sex‐linkage creates a ‘magic trait’ in a butterfly hybrid zone

Danaus chrysippus (L.) in Africa comprises four substantially isolated semispecies that are migratory and hybridize on a seasonal basis throughout the eastern and central part of the continent. In the hybrid zone (but not elsewhere), the butterfly is commonly host to a male killing endosymbiotic bacterium, Spiroplasma sp., which principally infects one semispecies, Danaus chrysippus chrysippus in Kenya. A W‐autosome mutation, inherited strictly matrilinearly, links B and C colour gene loci, which have thus gained sex‐linkage in chrysippus. We have monitored variation in sex ratio and genotype at the A and C colour gene loci for two extended periods of 18 months (2004–5) and 12 months (2009–10) in adults reared from wild eggs laid on trap plants in Kasarani, near Nairobi, Kenya. Additionally, in 2009–10, all surviving adult butterflies were screened for Spiroplasma infection. The hybridizing Kasarani population is highly atypical in three respects, and has apparently been so for some 30 years: first, the sex ratio is permanently female‐biased (as expected), although subject to seasonal fluctuation, being lowest (male/female) when D. c. chrysippus (cc) peaks and highest when Danaus chrysippus dorippus (CC) predominates; second, the population is invariably dominated by Cc heterozygotes of both sexes but especially females; and third, cc males are always scarce because they are systematically eliminated by male killing, whereas the CC genotype is male‐biased. It is this imbalance of sex versus genotype that determines the massive departure from Hardy–Weinberg equilibrium in the population, in part because cc females have little choice but to pair with C‐ males. We suggest that: first, Cc hybrids of both sexes fail to disperse in the company of either parental semispecies; second, Spiroplasma positive females carrying the W‐autosome mutation have a selective advantage over females that lack the translocation; third, the endoparasite and the translocation create a ‘magic trait’ linkage group that underlies hologenomic reproductive isolation between two emerging species, D. c. chrysippus and D. c. dorippus; and, fourth, that the predominance of males in dorippus suggests that individuals must be protected by a male‐killing suppressor gene. By contrast to the C locus, Aa heterozygotes are in substantial and permanent deficit, suggesting either assortative mating between AA (chrysippus and dorippus) and aa (Danaus chrysippus alcippus), or heterozygote unfitness, or both. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 92–109.     

The Caenorhabditis elegans spe‐49 gene is required for fertilization and encodes a sperm‐specific transmembrane protein homologous to SPE‐42

Fertilization, the fusion of sperm and oocyte to form a zygote, is the first and arguably the most important cell–cell interaction event in an organism’s life. Forward and reverse genetic approaches in the nematode Caenorhabditis elegans have identified many genes that are required for gametogenesis and fertilization and thus are beginning to elucidate the molecular pathways that underlie these processes. We identified an allele of the spe‐49 gene in a second filial generation (F₂) mutagenesis screen for spermatogenesis‐defective (spe) mutants. Mutant worms for spe‐49 produce sperm that have normal morphology, activate to form ameboid spermatozoa, and can migrate to and maintain their position in the hermaphrodite reproductive tract but fail to fertilize oocytes. This phenotype puts spe‐49 in the spe‐9 class of late‐acting genes that function in sperm at the time of fertilization. We cloned the spe‐49 gene through a combination of deficiency mapping, transgenic rescue, and genomic sequencing. spe‐49 messenger RNA (mRNA) is enriched in male germ cells, and the complementary DNA (cDNA) encodes a predicted 772‐amino‐acid six‐pass transmembrane protein that is homologous to SPE‐42. Indeed, SPE‐49 and SPE‐42 have identical predicted membrane topology and domain structure, including a large extracellular domain with six conserved cysteine residues, a DC‐STAMP domain, and a C‐terminal cytoplasmic domain containing a C4–C4 RING finger motif. The presence of two SPE‐42 homologs in animal genomes from worms to humans suggests that these proteins are highly conserved components of the molecular apparatus required for the sperm–oocyte recognition, binding, and fusion.     

NEUTRAL LIPIDS AS MAJOR STORAGE PRODUCTS IN ZOOSPORES OF THE GIANT KELP MACROCYSTIS PYRIFERA (PHAEOPHYCEAE)1

Neutral lipids, consisting primarily of triacylglycerols, were found to be a major form of carbon reserve in zoospores of the giant kelp Macrocystis pyrifera (L.) C. Ag. The fluorescent stain Nile Red revealed large lipid droplets in the posterior end of the cell, which comprised 20–41% of cellular carbon in newly released spores. Flow cytometric analyses of newly released spores stained with Nile Red revealed considerable variation in the neutral lipid content among spores that was independent of spore size. Lipid droplets were consumed during germination in spores maintained either under constant light or in continual darkness. The availability of light appeared to delay, but did not preclude, lipid use. The rate of lipid use during germination varied considerably among germlings with some cells consuming all of their lipid reserves within 5 h after release. In addition to zoospores, lipid droplets were observed in both male and female gametes. Numerous droplets were observed in eggs, while single lipid droplets were observed in sperm. Neutral lipid droplets were not observed in gametophytes or sporophytes except in developing gametes and spores. Large lipid reserves thus seem to be confined to the microscopic life history stages that presumably have relatively high energy demands. By serving as a supplemental fuel reserve, neutral lipids may be important in extending the effective range of zoospore dispersal.     

普通小麦×根茎冰草×黑麦三属杂种自交可育性的细胞学机理

普通小麦（ＴｒｉｔｉｃｕｍａｅｔｉｖｕｍＬ．,２ｎ＝６ｘ＝４２;ＡＡＢＢＤＤ）和根茎冰草（ＡｇｒｏｐｙｒｏｎｍｉｃｈｎｏｉＲｅｓｈｅｖ．,２ｎ＝４ｘ＝２８;ＰＰＰＰ）间的Ｆ１杂种（２ｎ＝５ｘ＝３５：ＡＢＤＰＰ）与两个黑麦（ＳｅｃａｌｅｃｅｒｅａｌｅＬ．,２ｎ＝２ｘ＝１４;ＲＲ）品种杂交,产生了自交可育的三属杂种。经细胞学研究表明,这种自交可育性是由于在某些细胞中通过两种方式发生了第一次减数分裂的失败,即单价染色体在赤道板发生分裂和单价染色体在一极的聚集,从而异致了有功能的雌、雄配子的形成。有功能配子的形成受染色体配对频率、基因型和环境状况的影响。冰草属的Ｐ染色体组存在染色体分离的控制基因,从而引起含有冰草属的杂种能够形成有功能的配子且自交可育。