Genetical study on the parthenogenesis in Laminaria japonica

The parthenogenesis and natural doubling of chromosomes in wild type female gametophytes of Laminaria japonica were studied. The results indicate that not all the female gametophytes from the wild type hybrid parent can propagate through parthenogenesis. Most parthenosporophytes can mature, their spores germinate into gametophytes, the latter then developed into female sporophytes. To form these parthenosporophytes the natural doubling of chromosomes occurred mainly at the first and second cell divisions of the spores. It is thus considered that the parthenogenesis of L. japonica is inheritable and the relative genes link closely with the genes controlling the natural doubling of chromosomes and the female determination.

Induction of Parthenogenesis in Plants and Application in Breeding

Parthenogenesis is a kind of reproductive mode by which the egg develops into embryo without fertilization and grows into plant finally. This article summarizes the advances of inducing parthenogenesis in plants in relation to induction methods, affecting factors and the studies in embryology. In addition, the application of parthenogenesis in breeding is also discussed.

Parthenogenesis and activation of mammalian oocytes for <i>in vitro</i>embryo production: A review

Parthenogenesis is a form of asexual reproduction found in females, where growth and development of embryos occurs without fertilization by a male. Parthenogenesis occurs naturally in aphids, Daphnia, rotifers, nematodes and some other invertebrates but can also be induced efficiently in mammalian oocytes by providing appropriate stimuli invitro. Recently, parthenogenesis has attracted wide attention because of the role of activated oocytes in the field of research that have been described such as intra cytoplasmic sperm injection, cloning by nuclear transfer, somatic cell cloning, investigating culture conditions etc. & potential for deriving pluripotent stem cell lines and their differentiation into various cell lines that can be utilized for various tissue engineering applications. The parthenogenetically activated oocytes possess maternal genome and can developed in to either haploid, diploid or polyploidy embryos with the help of it we can analyze the possible role of all the genes involved in imprinting processes as well as the role the paternal genome plays during early embryo development by comparing them with fertilized embryos. Several methods are able to induce parthenogenetic activation through the elevation of cytoplasmic free calcium in oocytes. But one common, universal method or activation agents has not been developed for all species because the process is highly specific for each species. Therefore, activation step for each species need to be optimized accordingly. This review describes the general method of activation of mammalian oocytes and their genomic imprinting analysis.

Novel microsatellite markers suggest the mechanism of parthenogenesis in Extatosoma tiaratum is automixis with terminal fusion

Parthenogenetic reproduction is taxonomically widespread and occurs through various cytological mechanisms, which have different impact on the genetic variation of the offspring. Extatosoma tiaratum is a facultatively parthenogenetic Australian insect （Phasmatodea）, in which females oviposit continuously throughout their adult lifespan irre- spective of mating. Fertilized eggs produce sons and daughters through sexual reproduction and unfertilized eggs produce female offspring via parthenogenesis. Here, we developed novel microsatellite markers for E. tiaratum and characterized them by genotyping indi- viduals from a natural population. We then used the microsatellite markers to infer the cytological mechanism of parthenogenesis in this species. We found evidence suggesting parthenogenesis in E. tiaratum occurs through automixis with terminal fusion, resulting in substantial loss of microsatellite heterozygosity in the offspring. Loss of microsatel- lite heterozygosity may be associated with loss of heterozygosity in fitness related loci. The mechanism of parthenogenetic reproduction can therefore affect fitness outcomes and needs to be considered when comparing costs and benefits of sex versus parthenogenesis.

“胰岛素-转铁蛋白-硒钠”对山羊卵母细胞体外成熟及胚胎发育的影响(英文)

[Objective] The research aimed to enhance culture efficiencies of oocyte and embryo of goat in vitro and to explore serum-free culture system in vitro.[Method] At present,the conventional solutions of oocyte maturation and embryo development in vitro were always added into 1% ITS(Insulin-transferrin-selenium) or using 1% ITS to replace FBS in 2 kinds culture solutions for conducting in vitro cultures of goat oocyte and parthenogenetic embryo.The influences of ITS on their developments were detected.[Result] ITS in maturation liquid of oocytes could not increase oocytes maturation rate but significantly increased blastocyst rate (58.06% vs. 48.19%)of parthenogenetic embryo.If FBS in maturation liquid of oocytes was replaced by ITS, the maturation rate, cleavage rate and blastocyst rate were basically unchanged.Adding ITS into embryo medium could increase blastocyst rate (68.30% vs. 56.82%)of parthenogenetic embryo of goat.If FBS in embryo medium was replaced by ITS,the cleavage rate didn’t change basically,while the blastocyst rate in ITS was obviously lower than that in FBS group(42.33% vs.56.82%).[Conclusion] ITS could promote maturation of oocyte in vitro and early embryonic development, in addition,ITS could replace serum in maturation medium of oocyte as serum-free culture system for conducting relevant researches.

Differentiation of neuron-like cells from mouse parthenogenetic embryonic stem cells

Parthenogenetic embryonic stem cells have pluripotent differentiation potentials, akin to fertilized embryo-derived embryonic stem cells. The aim of this study was to compare the neuronal differentiation potential of parthenogenetic and fertilized embryo-derived embryonic stem cells. Before differentiation, karyotype analysis was performed, with normal karyotypes detected in both parthenogenetic and fertilized embryo-derived embryonic stem cells. Sex chromosomes were identified as XX. Immunocytochemistry and quantitative real-time PCR detected high expression of the pluripotent gene, Oct4, at both the mRNA and protein levels, indicating pluripotent differentiation potential of the two embryonic stem cell subtypes. Embryonic stern cells were induced with retinoic acid to form embryoid bodies, and then dispersed into single cells. Single cells were differentiated in N2 differentiation medium for 9 days. Immunocytochemistry showed parthenogenetic and fertilized embryo-derived embryonic stem cells both express the neuronal cell markers nestin, ~lll-tubulin and myelin basic protein. Quantitative real-time PCR found expression of neuregenesis related genes （Sox-1, Nestin, GABA, Pax6, Zic5 and Pitxl） in both types of embryonic stem cells, and Oct4 expression was significantly decreased. Nestin and Pax6 expression in parthenogenetic embryonic stem cells was significantly higher than that in fertilized embryo-derived embryonic stem cells. Thus, our experimental findings indicate that parthenogenetic embryonic stem cells have stronger neuronal differentiation potential than fertilized embryo-derived embryonic stem cells.

Reproductive polyphenism and its advantages in aphids:Switching between sexual and asexual reproduction

Reproductive polyphenism,which allows one genotype to produce sexual and asexual morphs,is an extreme case of phenotypic plasticity and is commonly observed in aphids.Aphids are typical species that switch these reproductive modes,and the pathway orientation is triggered by the environmental conditions(mainly photoperiod and temperature).The typical arm ual life of aphids in eludes a successi on of parthenogenetic gen erations duri ng the spri ng and summer and a single sexual generation in autumn.In this review,we describe how the environmental cues orientate the reproductive mode of aphids from photoperiodic perception to endocrine regulation,and how juvenile hormones may act on the target cells(oocytes)to initiate the gametogenesis and embryogenesis in sexual and asexual reproduction.We also discuss the paradox of sex,especially the advantages of sexual reproduction in aphids.With the recent development of genomic resources in aphids,many potential genes involved in the reproductive polyphenism will enter the public's awareness.In particular,we describe a novel RNAi method in aphids,which may provide a molecular technique for determining the developmental fate and multiple reproductive strategies.

First record of Ulva californica in the mainland of China:a single alien parthenogenetic population in discontinuous distribution

Molecular investigations have raised concerns about the ecological risks of green tides caused by alien Ulva species in new habitats.The green tide-forming species U.californica Wille was generally considered to be native to North America,but new records have been widely reported in Europe,Asia,and Oceania in recent decades,indicating a strong dispersal capacity of the species.In this study,the first record of U.californica on the coastline of China's Mainland was reported,following a combined identification with multi-molecular markers and morphological characterization.It was shown that this species has a discontinuous distribution pattern along the coast of China's Mainland,with northern populations in the Yellow Sea and southern populations in the East China Sea and South China Sea.According to results of examination for life cycles and identification with mating type(MT)genetic markers,it was indicated that all U.californica samples were male gametophytes,and reproduced themselves through parthenogenesis solely.Combined with the fact that southern and northern populations are highly genetically identical,here we believed that U.californica was a recent alien species to China's Mainland with a rapid local spread.This finding provided evidences that the ability to reproduce in a variety of ways may play an important role in the spread of Ulva species,as well as essential basic data for marine risk management of green tides in China.In addition,according to the phylogeographic analysis,the possible geographical origin and global dispersal routes of U.californica were also proposed.

Collection of superovulated mouse oocytes continuously by surgery and their development after activation

Objective:To establish a new way to collect superovulated oocytes or zygotes repeatedlyfrom an individual mouse.Methods:Superovulations were induced by injection PMSG and hCG in Kunming strainmice.The ampullaes of oviduct of all anaesthetised mouse were put in a specially designed'U'sink and released.The second and third times of PMSG injection were made on the sixth day andeleventh day after the first superovulation injection.The capacity of development was examinedby in vitro culture of parthenogenesis activation oocytes.Results:Development to blastocyst stage was not significantly different between the first andsecond time collection.The percentage of blastocyst stage in CD and Sr^(++) treatment was signifi-cantly higher(P<0.05)than the oocytes treated in CB and Sr^(++).Conclusion:This method enables us to collect oocytes or zygotes repeatedly from one individ-ual mouse in an interval as short as 5 days and without influence on the quality of oocytes.

温度对棉蚜实验种群的影响

本实验是在恒温下进行的。结果表明,随着温度的增高,初产若蚜的体重逐渐减轻。因而采用校正产蚜量的新方法建立了五种温度(15、18、22、25及29℃)下的时间繁殖特征生命表。其结论是:1)随着温度的增高,平均世代历期和生态寿命逐渐缩短;2)存活曲线为B型。年龄特征产若率呈瑞利分布;3)在稳定年龄组配中,若虫占60.69～71.85％,成虫占28.15～39.31％。内禀增长能力(人)与温度呈抛物线关系。当温度为23.75℃时,rm理论值最大。

Reproductive biology of harvestmen(Arachnida:Opiliones):a review of a rapidly evolving research field

Harvestmen are a major arachnid order that has experienced a dramatic increase in biological knowledge in the 21st century.The publication of the book Harvestmen:The Biology of Opiliones in 2007 stimulated the development of many behavioral studies.Although the book is relatively recent,our understanding of the reproductive biology of harvestmen is already outdated due to the fast accumulation of new data.Our goal is to provide an updated review of the subject to serve as a benchmark for the following years.In the pre-copulatory phase,we explore the evolu-tion of facultative parthenogenesis,the factors that may affect the types of mating system,and the role of nuptial gifts in courtship.Regarding the copulatory phase,harvestmen are unique arachnids because they have aflagellate spermatozoa and a penis with complex morphology.We discuss the implications of these two features for sperm competition and cryptic female choice.In the post-copulatory phase,we connect ovi-position site selection and climate conditions to the widespread occurrence of resource defense polygyny,alternative reproductive tactics,and sexual dimorphism in several clades of tropical harvestmen.Finally,we present the different forms of parental care in the order,and discuss the benefits and costs of this behavior,which can be performed either by females or males.Throughout the review,we indicate gaps in our knowl-edge and subjects that deserve further studies.Hopefully,the information synthesized here will stimulate researchers worldwide to embrace harvestmen as a study system and to improve our effort to unravel the mysteries of their reproductive biology.

Genetic distinctness of parthenogenetic forms of European Polydrusus weevils of the subgenus Scythodrusus

Among eight species of Polydrusus weevils which belong to subgenus Scythodrusus, at least two possess parthenogenetic forms： P （S.） inustus and P （S.）pilifer. Both of these species consist of dioecious populations in the Caspian area and of parthenogenetic populations in Eastern Europe （R （S.） inustus）, the Caucasus region （both species） and Middle Asia （P （S.）pilifer）. The origin of parthenogenesis in this subgenus is unresolved; however some data suggest that the parthenogenetic forms are of hybrid ancestry. The genetic distinctness of parthenogenetic Scythodrusus was assessed on the basis of COII, ITS2, EFI-a and Wolbachia wsp, 16S ribosomal DNA, ftsZ and hcpA sequence comparisons. Both taxa turned out to be monophyletic for all markers, which is an evidence against hybridization of their dioecious ancestors. On the other hand, a high frequency of heterozygous P （S.） inustus females suggests an origin resulting from hybridization between genetically distinct dioecious representatives of this species. Very similar strains of Wolbachia supergroup A were found in both species, indicating that they have been either inherited from a common ancestor or were transmitted between parthenogenetic Scythodrusus weevils and probably spread randomly across their ranges.

Mitochondrial DNA suggests a single maternal origin for the widespread triploid parthenogenetic pest species, Paratanytarsus grimmii, but microsatellite variation shows local endemism

Parthenogenesis is common among invasive pest species, with many partheno- genetic species also showing polyploidy. Parthenogenetic polyploid species often have multiple hybrid origins and the potential to rapidly spread over vast geographical ar- eas. In this study, we examine patterns of mitochondrial and microsatellite variation in a widespread triploid parthenogenetic chironomid pest species, Paratanytarsus grimmii. Based on samples from five countries, including Australia, England, Germany, Japan, and Canada, we found extremely low mitochondrial diversity （〈0.14%）, with most individuals sharing a common and widespread haplotype. In contrast, microsatellite diversity revealed 41 clonal variants, which were regionally endemic. These findings suggest a single invasive maternal lineage ofP grimmii is likely to have recently spread over a broad geographical range. High levels of genotypic endemism suggest P grimmii populations have remained relatively isolated after an initial spread, with little ongoing migration. This, in part, can be attributed to rapid genetic differentiation via mutations of common clonal genotypes after P. grimmii spread, but multiple polyploidization and subsequent founder events are also likely to be contributing factors.

Microsatellites reveal the genetic structure of thelytokous strains of the migratory locust

This study reports on two parthenogenetic strains of the migratory locust Locusta migratoria. The offspring of thelytokou females had a single fragment per microsatellite loci. All offspring of the parthenogenetic F1 females were genetically identical. These results further confirmed that restitution of the sister products of early cleavage mitoses and cell fusion might be the most likely diploidization mechanisms in the thelytokous locusts. Polymerase chain reaction amplification results demonstrated that thelytoky in the locust was not induced by Wolbachia bacteria. Apart from the low fitness gained in thelytokous females, large populations with migration and losing heterozygosity may be other reasons why regular parthenogenesis has not evolved in the locust.