A cytoembryological study of Agrostis pilosula

1976 ◽  
Vol 54 (21) ◽  
pp. 2490-2496 ◽  
Author(s):  
M. Muniyamma
Keyword(s):  
Mother Cell ◽  
Female Gametophyte ◽  
Lateral Displacement ◽  
Embryo Sac ◽  
First Record ◽  
Mature Female ◽  
Egg Cell ◽  
Hormonal Imbalance ◽  
Endosperm Starch ◽  
Female Gametophyte Development

A detailed investigation of microsporogenesis, megasporogenesis, female gametophyte development, and embryogeny in Agrostis pilosula Trin. has been made. The chromosome number of 2n = 44 is the first record for this species. Pollen mother cell meiosis reveals normal chromosome behaviour. Microspore tetrads are mostly isobilateral. The bitegmic ovule is initially anatropous and becomes hemianatropous. The inner integument delimits the micropyle. A single archesporial cell, which is hypodermal or, more rarely, deeply seated in origin, directly functions as the megaspore mother cell. Meiosis usually results in the formation of a T-shaped tetrad of megaspores, but occasionally a linear triad of megaspores is seen instead. After three mitotic divisions, the chalazal megaspore gives rise to an eight-nucleate embryo sac. The mature female gametophyte is atypical because of the lateral displacement of antipodals and its triangular shape. It consists of two synergids, a pear-shaped egg slightly pushed aside, fused polar nuclei in close approximation to the egg cell, and three large ballooned laterally displaced coenocytic antipodal cells with hypertrophied nuclei. This antipodal condition might be associated with hormonal imbalance. The endosperm is free nuclear at first and leads to the formation of solid endosperm. Starch grains are observed in older cells of endosperm. The embryo development is regular and conforms to Pooid type.

scholarly journals Recent advances in understanding female gametophyte development

F1000Research ◽  
2018 ◽  
Vol 7 ◽  
pp. 804 ◽  
Author(s):  
Debra J Skinner ◽  
Venkatesan Sundaresan
Keyword(s):  
Cell Fate ◽  
Female Gametophyte ◽  
Cell Communication ◽  
Embryo Sac ◽  
Cell Types ◽  
Egg Cell ◽  
Male Gametes ◽  
Reproductive Unit ◽  
Genetic Mechanisms ◽  
Female Gametophyte Development

The haploid female gametophyte (embryo sac) is an essential reproductive unit of flowering plants, usually comprising four specialized cell types, including the female gametes (egg cell and central cell). The differentiation of these cells relies on spatial signals which pattern the gametophyte along a proximal-distal axis, but the molecular and genetic mechanisms by which cell identities are determined in the embryo sac have long been a mystery. Recent identification of key genes for cell fate specification and their relationship to hormonal signaling pathways that act on positional cues has provided new insights into these processes. A model for differentiation can be devised with egg cell fate as a default state of the female gametophyte and with other cell types specified by the action of spatially regulated factors. Cell-to-cell communication within the gametophyte is also important for maintaining cell identity as well as facilitating fertilization of the female gametes by the male gametes (sperm cells).

scholarly journals The mac1 Gene: Controlling the Commitment to the Meiotic Pathway in Maize

Genetics ◽  
1996 ◽  
Vol 142 (3) ◽  
pp. 1009-1020 ◽  
Author(s):  
William F Sheridan ◽  
Nadezhda A Avalkina ◽  
Ivan I Shamrov ◽  
Tatyana B Batyea ◽  
Inna N Golubovskaya
Keyword(s):  
Female Gametophyte ◽  
Embryo Sac ◽  
Flowering Plants ◽  
Normal Female ◽  
Ovule Development ◽  
Partial Sterility ◽  
Embryo Sac Formation ◽  
Female Gametophyte Development ◽  
Normal Meiosis ◽  
Pleiotropic Mutation

Abstract The switch from the vegetative to the reproductive pathway of development in flowering plants requires the commitment of the subepidermal cells of the ovules and anthers to enter the meiotic pathway. These cells, the hypodermal cells, either directly or indirectly form the archesporial cells that, in turn, differentiate into the megasporocytes and microsporocytes. We have isolated a recessive pleiotropic mutation that we have termed multiple archesporial cells1 (macl) and located it to the short arm of chromosome 10. Its cytological phenotype suggests that this locus plays an important role in the switch of the hypodermal cells from the vegetative to the meiotic (sporogenous) pathway in maize ovules. During normal ovule development in maize, only a single hypodermal cell develops into an archesporial cell and this differentiates into the single megasporocyte. In macl mutant ovules several hypodermal cells develop into archesporial cells, and the resulting megasporocytes undergo a normal meiosis. More than one megaspore survives in the tetrad and more than one embryo sac is formed in each ovule. Ears on mutant plants show partial sterility resulting from abnormalities in megaspore differentiation and embryo sac formation. The sporophytic expression of this gene is therefore also important for normal female gametophyte development.

Ovule and Female Gametophyte Development in Fertile and Sterile Safflower Plants (Carthamus tinctorius L.)

1989 ◽  
Vol 37 (6) ◽  
pp. 519 ◽  
Author(s):  
J Carapetian ◽  
EA Rupert
Keyword(s):  
Cell Differentiation ◽  
Female Gametophyte ◽  
Embryo Sac ◽  
Carthamus Tinctorius ◽  
Gametophyte Development ◽  
Male Gametogenesis ◽  
Delayed Initiation ◽  
Rapid Elongation ◽  
Functional Megaspore ◽  
Female Gametophyte Development

Development of safflower ovules and female gametophytes was compared in fertile and genetically sterile F2 and backcross segregants from the cross between 'US-10' and '57-147' genotypes. Fertile plants formed normal anatropous ovules with eight-nucleate embryo sacs, typical of the angiosperms. One week before anthesis, the eight-nucleate embryo sac is well developed and undergoes rapid elongation and expansion during the 24 h prior to anthesis, accompanied by a doubling in length of the florets. Sterile plants also formed normal ovules, but apparently with a delayed initiation of meiosis which was subsequently arrested at Metaphase I. Embryo sacs did not form in sterile florets except for rare observations of uninucleate embryo sacs which began to degenerate before anthesis. The integumentary tapetum which normally developed upon completion of meiosis in fertile plants, was well developed during Prophase I of megasporogenesis in sterile plants. This observation suggests that cell differentiation and development of this nutritive jacket is basically controlled by the age of the ovules rather than initiated by appearance of the functional megaspore. Failure of both female and male gametogenesis seems to result from interaction of three independently segregating genes.

Megagametogenesis, fertilization, and embryo development in Larixdecidua

1986 ◽  
Vol 16 (6) ◽  
pp. 1301-1309 ◽  
Author(s):  
Grzegorz Kosiński
Keyword(s):  
Cell Wall ◽  
Sexual Reproduction ◽  
Mother Cell ◽  
Megaspore Mother Cell ◽  
Female Gametophyte ◽  
Nuclear Stage ◽  
Empty Seed ◽  
Development Failure ◽  
Major Factors ◽  
Female Gametophyte Development

The phenology of sexual reproduction in Larixdecidua Mill, varies from year to year, and some intra- and inter-clonal differences were also found. Megaspore mother cell meiosis occurred at the time of pollination, during the second half of April, resulting in three or four megaspores. The free nuclear stage and cell wall and archegonia formation were completed in late May and the first half of June. An average of four archegonia was observed in each ovule, but the number ranged from two to six. Fertilization occurred during the first 20 days of June, about 7 weeks after pollination. A four-tiered, 16-celled proembryo formed. Meristematic regions formed in the embryo from the end of June to mid-July. Fully developed embryos were observed in mid-August. Simple polyembryony and delayed cleavage polyembryony were observed. Lack of pollination, disturbances during megasporogenesis and female gametophyte development, failure of fertilization, and embryo degeneration are the major factors resulting in empty seed.

Anther and Ovule Development in Tasmannia (Winteraceae)

1992 ◽  
Vol 40 (6) ◽  
pp. 877 ◽  
Author(s):  
N Prakash ◽  
AL Lim ◽  
FB Sampson
Keyword(s):  
Mother Cell ◽  
Female Gametophyte ◽  
Cell Plate ◽  
Basic Type ◽  
Ovule Development ◽  
Linear Tetrad ◽  
Polygonum Type ◽  
Secretory Type ◽  
Mother Cells ◽  
Female Gametophyte Development

Three species of Tasmannia R.Br. ex DC., T. glaucifolia, T. insipida and T. stipitata are studied. The anther is tetrasporangiate and its waU development conforms to the Basic type. The tapetum follows the secretory type of development. Cytokinesis in the microspore mother cells is simultaneous but an evanescent cell plate is present at telophase I and anaphase I1 during meiosis. Pollen tetrads are permanent and tetrahedral. The mature pollen is anaulcerate, reticulate and 2-celled. The ovule. is anatropous, bitegmic and crassinucellate. The micropyle in T. stipitata and T. Glaucifolia is formed by the inner integument only whereas in T. insipida it is formed by both the integuments and is zigzag in outline. Meiosis in the single megaspore mother cell produces a linear or T-shaped megaspore tetrad in T. stipitata and T. glaucifolia but only a linear tetrad in T. insipida. Female gametophyte development is of the monosporic Polygonum type. Fertilisation is porogamous; triple fusion and syngamy occur simultaneously.

scholarly journals Embryo development in Carica papaya Linn

2021 ◽  
Author(s):  
Miguel Acevedo-Benavides ◽  
Pablo Bolaños-Villegas
Keyword(s):  
Cell Fate ◽  
Female Gametophyte ◽  
Carica Papaya ◽  
Genetic Regulation ◽  
Draft Genome ◽  
Embryo Sac ◽  
Egg Cell ◽  
Parental Line ◽  
Before And After ◽  
Autonomous Development

ABSTRACTPapaya (Carica papaya Linn.) is a tropical plant whose draft genome has been sequenced. Papaya produces large fruits rich in vitamins A and C and is an important cash crop in developing countries. Nonetheless, little is known about how the female gametophyte develops, how it is fertilized and how it develops into a mature seed containing an embryo and an endosperm. The Papaya female gametophyte displays a Polygonum-type architecture consisting of two synergid cells, an egg cell, a central cell, and three antipodal cells. Reports are available of the presumed existence of varieties in which cross fertilization is bypassed and autonomous development of embryos occurs (e.g., apomixis). In this study, we analyzed the development of female gametophytes in a commercial Hawaiian parental line and in the presumed apomictic Costa Rican line L1. Samples were collected before and after anthesis to compare the overall structure, size and transcriptional patterns of several genes that may be involved in egg and endosperm cell fate and proliferation. These genes were the putative papaya homologs of ARGONAUTE9 (AGO9), MEDEA (MEA), RETINOBLASTOMA RELATED-1 (RBR1), and SLOW WALKER-1 (SWA1). Our results suggest that its feasible to identify the contour of structural features of Polygonum-type development, and that in bagged female flowers of line L1 we might have observed autonomous development of embryo-like structures. Possible downregulation of papaya homologs for AGO9, MEA, RBR1 and SWA1 was observed in embryo sacs from line L1 before and after anthesis, which may suggest a tentative link between suspected apomixis and transcriptional downregulation of genes for RNA-directed DNA methylation, histone remodelers, and rRNA processing. Most notably, the large size of the papaya embryo sac suggests that it could be a cytological alternative to Arabidopsis thaliana for study. Significant variation in embryo sac size was observed between the varieties under study, suggesting wide differences in the genetic regulation of anatomical features.

scholarly journals The dyad gene is required for progression through female meiosis in Arabidopsis

Development ◽  
2000 ◽  
Vol 127 (1) ◽  
pp. 197-207 ◽  
Author(s):  
I. Siddiqi ◽  
G. Ganesh ◽  
U. Grossniklaus ◽  
V. Subbiah
Keyword(s):  
Mother Cell ◽  
Megaspore Mother Cell ◽  
Female Gametophyte ◽  
Molecular Mechanisms ◽  
Higher Plants ◽  
Embryo Sac ◽  
Initial Step ◽  
Female Meiosis ◽  
Female Germ Cell ◽  
Further Development

In higher plants the gametophyte consists of a gamete in association with a small number of haploid cells, specialized for sexual reproduction. The female gametophyte or embryo sac, is contained within the ovule and develops from a single cell, the megaspore which is formed by meiosis of the megaspore mother cell. The dyad mutant of Arabidopsis, described herein, represents a novel class among female sterile mutants in plants. dyad ovules contain two large cells in place of an embryo sac. The two cells represent the products of a single division of the megaspore mother cell followed by an arrest in further development of the megaspore. We addressed the question of whether the division of the megaspore mother cell in the mutant was meiotic or mitotic by examining the expression of two markers that are normally expressed in the megaspore mother cell during meiosis. Our observations indicate that in dyad, the megaspore mother cell enters but fails to complete meiosis, arresting at the end of meiosis 1 in the majority of ovules. This was corroborated by a direct observation of chromosome segregation during division of the megaspore mother cell, showing that the division is a reductional and not an equational one. In a minority of dyad ovules, the megaspore mother cell does not divide. Pollen development and male fertility in the mutant is normal, as is the rest of the ovule that surrounds the female gametophyte. The embryo sac is also shown to have an influence on the nucellus in wild type. The dyad mutation therefore specifically affects a function that is required in the female germ cell precursor for meiosis. The identification and analysis of mutants specifically affecting female meiosis is an initial step in understanding the molecular mechanisms underlying early events in the pathway of female reproductive development.

scholarly journals Development of Female Gametophyte in Gladiolus italicus Miller (Iridaceae)

Caryologia ◽  
2021 ◽  
Vol 74 (3) ◽  
pp. 91-97
Author(s):  
Ciler Kartal ◽  
Nuran Ekici ◽  
Almina Kargacıoğlu ◽  
Hazal Nurcan Ağırman
Keyword(s):  
Light Microscopy ◽  
Female Gametophyte ◽  
Embryo Sac ◽  
Polygonum Type ◽  
Gametophyte Development ◽  
Embryo Sac Development ◽  
Secondary Nucleus ◽  
Microscopy Techniques ◽  
Female Gametophyte Development ◽  
First Time

In this study gynoecium, megasporogenesis, megagametogenesis and female gametophyte of Gladiolus italicus Miller were examined cytologically and histologically by using light microscopy techniques. Ovules of G. italicus are of anatropous, bitegmic and crassinucellate type. Embryo sac development is of monosporic Polygonum type. Polar nuclei fuse before fertilization to form a secondary nucleus near the antipodals. The female gametophyte development of G. italicus was investigated for the first time with this study.

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