Ontogenèse des sacs embryonnaires non réduits chez Eragrostis curvula

1986 ◽  
Vol 64 (8) ◽  
pp. 1778-1785 ◽  
Author(s):  
T. Rabau ◽  
B. Longly ◽  
B.-P. Louant
Keyword(s):  
Low Frequency ◽  
Reproductive Mode ◽  
Polar Nucleus ◽  
Egg Cell ◽  
Forage Grass ◽  
Female Development ◽  
Eragrostis Curvula ◽  
Male Development

The apomictic reproductive mode by diplospory is cytologically analysed in Eragrostis curvula (Schrad.) Nees, a tetraploid forage grass. The genesis of unreduced embryo sacs is followed; two kinds of sacs are then distinguished: (i) a monopolar one with a typical oogonial complex and a polar nucleus at the micropylar end; (ii) a bipolar one with an egg cell and two polar nuclei at the micropylar end, and some antipodial cells at the chalazal end. Monopolar sacs are 3 times more frequent than bipolar ones. Traces of sexuality are noted in E. curvula but with a low frequency. A chronology of female development is established according to stages of male development. This should make possible an early distinction and allow a useful comparison between diplospory and sexuality within the genus Eragrostis.

Apospory in Paspalum thunbergii

2004 ◽  
Vol 52 (1) ◽  
pp. 81 ◽  
Author(s):  
Guohua Ma ◽  
Xuelin Huang ◽  
Nanxian Zhao ◽  
Qiusheng Xu
Keyword(s):  
Chromosome Number ◽  
Developmental Stage ◽  
Pollen Viability ◽  
Paraffin Section ◽  
Embryo Sac ◽  
Low Frequency ◽  
The Other ◽  
Egg Cell ◽  
Successive Generations ◽  
Mother Cells

The cytology, development of aposporous embryo sac, pro-embryo and pseudogamy in Paspalum thunbergii Kunth ex Steud. was studied. P. thunbergii was found to be a tetraploid cytotype, with a chromosome number of 40. Meiosis of the pollen mother cells was irregular, pollen viability was low and multiporate pollens were often observed. Megasporogenesis began normally; however, the megaspore deteriorated at the developmental stage of tetrad, while one to five specific nucellar cells became active and began enlarging, and then developed into aposporous embryo sacs. The mature aposporous sacs usually had three nuclei characterised by one egg cell and two polar nuclei. The egg cell developed spontaneously to form pro-embryos prior to anthesis. When several aposporous sacs occurred in the same ovule, usually one sac near the micropyle was involved in pseudogamy, while the other sacs were not involved. Low frequency of twin-embryo seedlings was observed after seeds matured. Examination of three successive generations by paraffin-section and clearing methods revealed that no sexual sac was present. Therefore, the species P. thunbergii is considered to be an obligate apomict that reproduces by apospory.

scholarly journals SEX DETERMINATION IN THE NEMATODE C. ELEGANS: ANALYSIS OF tra-3 SUPPRESSORS AND CHARACTERIZATION OF fem GENES

Genetics ◽  
1986 ◽  
Vol 114 (1) ◽  
pp. 15-52
Author(s):  
Jonathan Hodgkin
Keyword(s):  
Sex Determination ◽  
Null Alleles ◽  
Temperature Sensitive ◽  
Female Development ◽  
C Elegans ◽  
Male Development ◽  
Maternal Contribution ◽  
New Gene ◽  
Extragenic Suppressors

ABSTRACT Mutations of the gene tra-3 result in partial masculinization of XX animals of C. elegans, which are normally hermaphrodites (males are XO). A total of 43 tra-3 revertants (one intragenic, 42 extragenic) have been isolated and analyzed, in the hope of identifying new sex-determination loci. Most (38) of the extragenic suppressors cause partial or complete feminization of XX and XO animals; the remaining four are weak suppressors. The feminizing suppressors are mostly alleles of known sex-determining genes: tra-1 (11 dominant alleles), tra-2 (one dominant allele), fem-1 (four alleles) and fem-2 (four alleles), but 18 are alleles of a new gene, fem-3. Additional alleles have been isolated for the fem-2 and fem-3 genes, as well as fem-3 deficiencies. Mutations in fem-3 resemble alleles of fem-1 (previously characterized): putative null alleles result in complete feminization of XX and XO animals, transforming them into fertile females. Severe alleles of fem-2 also cause complete feminization of XX animals at all temperatures, but feminization of fem-2 XO animals is temperature-sensitive: complete at 25°, incomplete at 20°. As with fem-1, severe mutations of fem-2 and fem-3 are wholly epistatic to masculinizing alleles of tra-2 and tra-3, and epistatic to tra-1 masculinizing alleles in the germline, but not in the soma. All three fem genes are essential for male development and appear to have a dual role in promoting spermatogenesis and repressing tra-1 activity. All three fem genes exhibit strong maternal effects; the maternal contribution of fem gene products may be inactivated in XX animals by a posttranscriptional mechanism. Maternal contributions of wild-type fem-3 product are necessary for normal XO male development and XX hermaphrodite (as opposed to female) development.

Evaluation of different methods for assessing the reproductive mode of weeping lovegrass plants, Eragrostis curvula (Schrad.) Nees

2011 ◽  
Vol 59 (3) ◽  
pp. 253 ◽  
Author(s):  
Mauro Meier ◽  
Diego Zappacosta ◽  
Juan Pablo Selva ◽  
Silvina Pessino ◽  
Viviana Echenique
Keyword(s):  
Flow Cytometry ◽  
Reproductive Mode ◽  
Forage Grass ◽  
Callose Deposition ◽  
Deposition Patterns ◽  
Content Ratio ◽  
The World ◽  
Progeny Tests ◽  
Sexual Processes

Weeping lovegrass is a forage grass cultivated in semiarid regions of the world that reproduces mainly by apomixis (diplospory), a process that involves the formation of asexual seeds and bypasses the processes of meiosis and fertilisation. The aim of this work was to evaluate and compare different techniques (cytoembryology, callose deposition, flow cytometry and progeny tests) to determine the reproductive mode of weeping lovegrass. Typical sexual and apomictic processes were clearly differentiated using cytoembryology, and different callose deposition patterns were observed in sexual and apomictic genotypes. Previous studies indicated that presence of callose on the cell wall of the megaspore mother cell is associated only with sexual processes. Nevertheless, our results also found callose deposition in apomictic genotypes, although clearly different from the pattern found in sexual processes, allowing discrimination between sexual and apomictic plants. Flow cytometry seed screening using individual seeds did not differentiate between sexual and apomictic plants as the embryo : endosperm DNA content ratio was similar in sexual and apomictic plants. Progeny tests using molecular markers showed uniform patterns in offspring from apomictic plants and variable patterns among the progeny of sexual plants. The results obtained from cytological studies and progeny tests were similar, indicating that both methods provide useful tools for determination of reproductive mode. However, the callose test with aniline blue was faster and easier to use than other techniques.

scholarly journals Infection Dynamics of Coexisting Beta- and Gammaproteobacteria in the Nested Endosymbiotic System of Mealybugs

2008 ◽  
Vol 74 (13) ◽  
pp. 4175-4184 ◽  
Author(s):  
Marie Kono ◽  
Ryuichi Koga ◽  
Masakazu Shimada ◽  
Takema Fukatsu
Keyword(s):  
Population Dynamics ◽  
Phylogenetic Analyses ◽  
Reproductive Activity ◽  
Adult Males ◽  
Female Development ◽  
Male Development ◽  
Infection Dynamics ◽  
Molecular Phylogenetic ◽  
Pseudococcus Comstocki

ABSTRACT We investigated the infection dynamics of endosymbiotic bacteria in the developmental course of the mealybugs Planococcus kraunhiae and Pseudococcus comstocki. Molecular phylogenetic analyses identified a betaproteobacterium and a gammaproteobacterium from each of the mealybug species. The former bacterium was related to the β-endosymbionts of other mealybugs, i.e., “Candidatus Tremblaya princeps,” and formed a compact clade in the Betaproteobacteria. Meanwhile, the latter bacterium was related to the γ-endosymbionts of other mealybugs but belonged to distinct clades in the Gammaproteobacteria. Whole-mount in situ hybridization confirmed the peculiar nested formation in the endosymbiotic system of the mealybugs: the β-endosymbiont cells were present in the cytoplasm of the bacteriocytes, and the γ-endosymbiont cells were located in the β-endosymbiont cells. In nymphal and female development, a large oval bacteriome consisting of a number of bacteriocytes was present in the abdomen, wherein the endosymbionts were harbored. In male development, strikingly, the bacteriome progressively degenerated in prepupae and pupae and became almost unrecognizable in adult males. In the degeneration process, the γ-endosymbionts disappeared more rapidly than the β-endosymbionts did. Quantitative PCR analyses revealed that (i) the population dynamics of the endosymbionts in female development reflected the reproductive activity of the insects, (ii) the population dynamics of the endosymbionts were strikingly different between female development and male development, (iii) the endosymbiont populations drastically decreased in male development, and (iv) the γ-endosymbiont populations decreased more rapidly than the β-endosymbiont populations in male development. Possible mechanisms underlying the uncoupled regulation of the β- and γ-endosymbiont populations are discussed in relation to the establishment and evolution of this unique prokaryote-prokaryote endosymbiotic system.

scholarly journals The TRANSFORMER Genes of the Fern Ceratopteris Simultaneously Promote Meristem and Archegonia Development and Repress Antheridia Development in the Developing Gametophyte

Genetics ◽  
1997 ◽  
Vol 147 (4) ◽  
pp. 1885-1897 ◽  
Author(s):  
Jo Ann Banks
Keyword(s):  
Sex Determination ◽  
Sex Expression ◽  
The Other ◽  
Female Development ◽  
Epistatic Interactions ◽  
Male Development ◽  
Sporophyte Development

Abstract The sex of the haploid gametophyte of the fern Ceratopteris is determined by the presence or absence of the pheromone antheridiogen, which, when present, promotes male development and represses female development of the gametophyte. Several genes involved in sex determination in Ceratopteris have been identified by mutation. In this study, the epistatic interactions among new and previously described sex-determining mutants have been characterized. These results show that sex expression is regulated by two sets of genes defined by the FEM1 and TRA loci. Each promotes the expression of either male or female traits and simultaneously represses the expression of the other. A model describing how antheridiogen regulates the expression of these genes and the sex of the gametophyte is described. The observation that some gametophytic sexdetermining mutants have phenotypic effects on the spore phyte plant indicates that sex determination in the Ceratopteris gametophyte is regulated by a mechanism that also regulates sporophyte development.

scholarly journals The ultrastructure of the mature embryo sac in the natural tetraploid of red clover (Trifolium pratense L.): that has a very low rate of seed formation

2014 ◽  
Vol 66 (1) ◽  
pp. 13-20 ◽  
Author(s):  
Gönül Algan ◽  
H. Nurhan Bakar
Keyword(s):  
Endoplasmic Reticulum ◽  
Trifolium Pratense ◽  
Embryo Sac ◽  
Red Clover ◽  
Mature Embryo ◽  
Polar Nucleus ◽  
Central Cell ◽  
Egg Cell ◽  
Ultrastructural Organization ◽  
Seed Formation

In this study, ultrastructural organization of cells in the mature embryo sac of natural tetraploid <em>Trifolium pratense</em> L. was investigated. The mature embryo sac of this plant contains an egg cell with two synergids at the micropylar end, and a central cell with two polar nuclei. The ultrastructure of these cells agrees with what is known for most angiosperms studied with the electron microscope. The egg cell is a large and highly vacuolate cell, partially surrounded by a wall. Much of the cytoplasm is located around the nucleus at the chalazal end and there are few numbers of channel-shaped endoplasmic reticulum, mitochondria, plastids and numerous ribosomes distributed throughout the cytoplasm. Unlike the egg cell, much of the cytoplasm in synergid cells is located at micropylar part of the cell and the synergid cytoplasm contains especially, large numbers of rough endoplasmic reticulum, free ribosomes, mitochondria and plastids. The central cell of <em>T. pratense</em> L. contains two large polar nuclei which lie close to the egg apparatus. Each polar nucleus has a single, large, dense nucleolus that contains several nucleolar vacuoles. Much of the central cell cytoplasm consisting of granular and agranular endoplasmic reticulum, mitochondria, plastids, ribosomes, dictyosomes and lipid bodies are placed around polar nuclei.

Genetic control of sex determination in the germ line of Caenorhabditis elegans

1988 ◽  
Vol 322 (1208) ◽  
pp. 11-18 ◽  
Keyword(s):  
Caenorhabditis Elegans ◽  
Sex Determination ◽  
Genetic Control ◽  
Germ Line ◽  
Female Development ◽  
Tissue Specific ◽  
C Elegans ◽  
Male Development

The nematode Caenorhabditis elegans normally exists as one of two sexes: self-fertilizing hermaphrodite or male. Development as hermaphrodite or male requires the differentiation of each tissue in a sex-specific way. In this review, I discuss the genetic control of sex determination in a single tissue of C. elegans : the germ line. Sex determination in the germ line depends on the action of two types of genes: - those that act globally in all tissues to direct male or female development and those that act only in the germ line to specify either spermatogenesis or oogenesis. First, I consider a tissue-specific sex-determining gene, fog-1 , which promotes spermatogenesis in the germ line. Second, I consider the regulation of the hermaphrodite pattern of germ ­ line gametogenesis where first sperm and then oocytes are produced.

scholarly journals Triploid plover female provides support for a role of the W chromosome in avian sex determination

2012 ◽  
Vol 8 (5) ◽  
pp. 787-789 ◽  
Author(s):  
Clemens Küpper ◽  
Jakob Augustin ◽  
Scott Edwards ◽  
Tamás Székely ◽  
András Kosztolányi ◽  
...  
Keyword(s):  
Sex Determination ◽  
Sex Chromosome ◽  
W Chromosome ◽  
Female Development ◽  
Linked Gene ◽  
Charadrius Alexandrinus ◽  
Male Development ◽  
Polymorphic Microsatellite ◽  
Kentish Plover

Two models, Z Dosage and Dominant W , have been proposed to explain sex determination in birds, in which males are characterized by the presence of two Z chromosomes, and females are hemizygous with a Z and a W chromosome. According to the Z Dosage model, high dosage of a Z-linked gene triggers male development, whereas the Dominant W model postulates that a still unknown W-linked gene triggers female development. Using 33 polymorphic microsatellite markers, we describe a female triploid Kentish plover Charadrius alexandrinus identified by characteristic triallelic genotypes at 14 autosomal markers that produced viable diploid offspring. Chromatogram analysis showed that the sex chromosome composition of this female was ZZW. Together with two previously described ZZW female birds, our results suggest a prominent role for a female determining gene on the W chromosome. These results imply that avian sex determination is more dynamic and complex than currently envisioned.

scholarly journals The role of the Wolffian ducts in the formation of the sinus vagina: an organ culture study

Development ◽  
1983 ◽  
Vol 73 (1) ◽  
pp. 275-295
Author(s):  
Gabriele Bok ◽  
Ulrich Drews
Keyword(s):  
Organ Culture ◽  
Mouse Embryos ◽  
The Other ◽  
Urogenital Sinus ◽  
Female Development ◽  
Culture Study ◽  
Male Development ◽  
Stage Of Development ◽  
Sinus Formation

In mammals formation of a sinus vagina is inhibited in the male by endogenous testosterone from the embryonic testes. To answer the question which morphogenetic events during formation of thevagina are influenced by testosterone, we explanted genital tracts of mouse embryos in the indifferent stage of development in organ culture. Half of the explants were treated with testosterone and therefore developed in male direction. The other half was kept without testosterone and developed constitutively in female direction. Since the antiMüller factor was not present, in both types of cultures the Müllerian ducts were preserved. During female development the Müllerian ducts fused with the dorsolaterally apposed caudal segments of the Wolffian ducts. Thus the caudal segments of the Wolffian ducts were incorporated in the vaginal plate, while cranially the Wolffian ducts degenerated as expected. During male development fusion between Müllerian and Wolffian ducts did not occur. Under the influence of testosterone the respective caudal segments of the Wolffian ducts were surrounded by dense mesenchyme and further male differentiation took place. We conclude that the ‘sinus protrusions’ or ‘sinovaginal bulbs’ observed during development of the vagina, are in fact the caudal segments of the Wolffian ducts. They serve as a link between Müllerian ducts and urogenital sinus. Formation of a sinus vagina is prevented by testosterone simply by induction of male development in this area.

scholarly journals Eragrostis curvula, a Model Species for Diplosporous Apomixis

Plants ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1818
Author(s):  
Jose Carballo ◽  
Diego Zappacosta ◽  
Juan Pablo Selva ◽  
Mario Caccamo ◽  
Viviana Echenique
Keyword(s):  
Small Rna ◽  
Embryo Sac ◽  
Genotyping By Sequencing ◽  
Reproductive Mode ◽  
Hybrid Vigour ◽  
Rna Seq ◽  
Model Species ◽  
Eragrostis Curvula ◽  
Embryo Sac Development ◽  
Mendelian Factor

Eragrostis curvula (Schrad.) Ness is a grass with a particular apomictic embryo sac development called Eragrostis type. Apomixis is a type of asexual reproduction that produces seeds without fertilization in which the resulting progeny is genetically identical to the mother plant and with the potential to fix the hybrid vigour from more than one generation, among other advantages. The absence of meiosis and the occurrence of only two rounds of mitosis instead of three during embryo sac development make this model unique and suitable to be transferred to economically important crops. Throughout this review, we highlight the advances in the knowledge of apomixis in E. curvula using different techniques such as cytoembryology, DNA methylation analyses, small-RNA-seq, RNA-seq, genome assembly, and genotyping by sequencing. The main bulk of evidence points out that apomixis is inherited as a single Mendelian factor, and it is regulated by genetic and epigenetic mechanisms controlled by a complex network. With all this information, we propose a model of the mechanisms involved in diplosporous apomixis in this grass. All the genetic and epigenetic resources generated in E. curvula to study the reproductive mode changed its status from an orphan to a well-characterised species.

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