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.

Embryological studies in the compositae, I. Sporogenesis, Gametogenesis, and Embryogeny in Cotula australis (Less.) Hook. F

1962 ◽  
Vol 10 (1) ◽  
pp. 1 ◽  
Author(s):  
GL Davis
Keyword(s):  
Mother Cell ◽  
Megaspore Mother Cell ◽  
Embryo Sac ◽  
Subsequent Development ◽  
Pollen Grains ◽  
Archesporial Cell ◽  
Polygonum Type ◽  
Wall Formation ◽  
Chalazal Megaspore

Cotula australis has a discoid heterogamous capitulum in which the outermost three whorls of florets are female and naked. The bisexual disk florets are fully fertile and have a four-lobed corolla with four shortly epipetalous stamens. The anthers contain only two microsporangia. Wall formation and microsporogenesis are described and the pollen grains are shed at the three-celled condition. The ovule is teguinucellate and the hypodermal archesporial cell develops directly as the megaspore mother cell. Megasporogenesis is normal and the monosporio embryo sac develops from the chalazal megaspore. Breakdown of the nucellar epidermis takes place when the embryo sac is binucleate and its subsequent development follows the Polygonum type. The synergids extend deeply into the micropyle and one persists until late in embryogeny as a haustorium. The development of the embryo is of the Asterad type, and the endosperm is cellular. C. coronopifolia agrees with C. australis in the presence of only two microsporangia in each anther and the development of a synergid haustorium.

Female gametophyte and embryo development in western hemlock (Tsuga heterophylla)

1974 ◽  
Vol 52 (4) ◽  
pp. 885-893 ◽  
Author(s):  
Elizabeth A. Stanlake ◽  
John N. Owens
Keyword(s):  
Embryo Development ◽  
Mother Cell ◽  
Megaspore Mother Cell ◽  
Morphological Study ◽  
Female Gametophyte ◽  
Tsuga Heterophylla ◽  
Western Hemlock ◽  
Seed Fall

A morphological study of the female gametophyte and embryo development was made for western hemlock (Tsuga heterophylla (Raf.) Sarg.) growing in the Victoria, B.C., area. Western hemlock follows a pattern of development similar to other members of the Pinaceae. A comparison was also made between development in western hemlock and other gymnosperm families. Meiosis of the megaspore mother cell in western hemlock begins in early February and is completed at the end of the first week in March. This is 3 weeks before pollination. Fertilization occurs 6 weeks after pollination, in the middle of May. Embryo development takes place throughout June and July and the embryo is mature by the middle of August. Seed fall occurs throughout September, 5 months after pollination.

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.

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.

Endothelial Dysfunction in Dyslipidaemia: Molecular Mechanisms and Clinical Implications

2020 ◽  
Vol 27 (7) ◽  
pp. 1021-1040 ◽  
Author(s):  
Bozidarka Zaric ◽  
Milan Obradovic ◽  
Andreja Trpkovic ◽  
Maciej Banach ◽  
Dimitri P. Mikhailidis ◽  
...  
Keyword(s):  
Endothelial Dysfunction ◽  
Molecular Mechanisms ◽  
Lymphatic Vessels ◽  
Lipoprotein Metabolism ◽  
Initial Step ◽  
Beneficial Effects ◽  
Relative Contribution ◽  
Vessel Remodeling ◽  
Vitamin C Supplementation ◽  
Further Development

The endothelium consists of a monolayer of Endothelial Cells (ECs) which form the inner cellular lining of veins, arteries, capillaries and lymphatic vessels. ECs interact with the blood and lymph. The endothelium fulfils functions such as vasodilatation, regulation of adhesion, infiltration of leukocytes, inhibition of platelet adhesion, vessel remodeling and lipoprotein metabolism. ECs synthesize and release compounds such as Nitric Oxide (NO), metabolites of arachidonic acid, Reactive Oxygen Species (ROS) and enzymes that degrade the extracellular matrix. Endothelial dysfunction represents a phenotype prone to atherogenesis and may be used as a marker of atherosclerotic risk. Such dysfunction includes impaired synthesis and availability of NO and an imbalance in the relative contribution of endothelialderived relaxing factors and contracting factors such as endothelin-1 and angiotensin. This dysfunction appears before the earliest anatomic evidence of atherosclerosis and could be an important initial step in further development of atherosclerosis. Endothelial dysfunction was historically treated with vitamin C supplementation and L-arginine supplementation. Short term improvement of the expression of adhesion molecule and endothelial function during antioxidant therapy has been observed. Statins are used in the treatment of hyperlipidaemia, a risk factor for cardiovascular disease. Future studies should focus on identifying the mechanisms involved in the beneficial effects of statins on the endothelium. This may help develop drugs specifically aimed at endothelial dysfunction.

The time and duration of female meiosis in wheat, rye and barley

1973 ◽  
Vol 183 (1072) ◽  
pp. 301-319 ◽  
Keyword(s):  
Hordeum Vulgare ◽  
Nuclear Dna ◽  
Higher Plants ◽  
Embryo Sac ◽  
Nuclear Dna Content ◽  
Male Meiosis ◽  
Female Development ◽  
Female Meiosis ◽  
Male And Female ◽  
Mother Cells

Few recent investigations have been made of female meiosis in cereals, and almost nothing is known about the duration of female meiosis in higher plants. Consequently, the time and duration of female meiosis in Triticum aestivum , Hordeum vulgare and Secale cereale have been studied. The appearance of the embryo sac mother cell (e. m. c.) and of the meiotic nuclei during female meiosis in Hordeum vulgare is described and illustrated. In the species studied, each floret contains only one ovary with a single e. m. c., and meiosis is almost synchronous in the pollen mother cells from all three anthers. Conse­quently, it is possible to make precise comparisons between the stages of male and female development within individual florets. Data from these comparisons, together with know­ledge previously determined of the duration of male meiosis in these species, allowed the estimation of the time and duration of female meiosis fairly accurately for T. aestivum and H. vulgare and approximately for S. cereale . The results showed that for H. vulgar and T. aestivum grown at 20°C, the duration of female meiosis was very similar to the duration of male meiosis. Furthermore, on average male and female meiosis occurred almost synchronously. In S. cereale however, male meiosis preceeded female meiosis by about 15 h. Growing T. aestivum under environmental stress induced asynchrony between male and female development at meiosis. Synchrony was not re-established after a long period under normal conditions. Nuclear DNA content and ploidy level are known to be important factors determining or affecting the duration of male meiosis. These factors appear to play an important role in controlling the duration of female meiosis also.

scholarly journals Embryo and Endosperm Development Is Disrupted in the Female Gametophytic capulet Mutants of Arabidopsis

Genetics ◽  
2002 ◽  
Vol 162 (4) ◽  
pp. 1911-1925
Author(s):  
Paul E Grini ◽  
Gerd Jürgens ◽  
Martin Hülskamp
Keyword(s):  
Seed Development ◽  
Transgene Expression ◽  
Female Gametophyte ◽  
Higher Plants ◽  
Embryo Sac ◽  
Endosperm Development ◽  
Wild Type ◽  
Paternal Genome ◽  
Early Stages ◽  
Gametic Imprinting

Abstract The female gametophyte of higher plants gives rise, by double fertilization, to the diploid embryo and triploid endosperm, which develop in concert to produce the mature seed. What roles gametophytic maternal factors play in this process is not clear. The female-gametophytic effects on embryo and endosperm development in the Arabidopsis mea, fis, and fie mutants appear to be due to gametic imprinting that can be suppressed by METHYL TRANSFERASE1 antisense (MET1 a/s) transgene expression or by mutation of the DECREASE IN DNA METHYLATION1 (DDM1) gene. Here we describe two novel gametophytic maternal-effect mutants, capulet1 (cap1) and capulet2 (cap2). In the cap1 mutant, both embryo and endosperm development are arrested at early stages. In the cap2 mutant, endosperm development is blocked at very early stages, whereas embryos can develop to the early heart stage. The cap mutant phenotypes were not rescued by wild-type pollen nor by pollen from tetraploid plants. Furthermore, removal of silencing barriers from the paternal genome by MET1 a/s transgene expression or by the ddm1 mutation also failed to restore seed development in the cap mutants. Neither cap1 nor cap2 displayed autonomous seed development, in contrast to mea, fis, and fie mutants. In addition, cap2 was epistatic to fis1 in both autonomous endosperm and sexual development. Finally, both cap1 and cap2 mutant endosperms, like wild-type endosperms, expressed the paternally inactive endosperm-specific FIS2 promoter GUS fusion transgene only when the transgene was introduced via the embryo sac, indicating that imprinting was not affected. Our results suggest that the CAP genes represent novel maternal functions supplied by the female gametophyte that are required for embryo and endosperm development.

The time and duration of female meiosis in Lilium

1975 ◽  
Vol 188 (1093) ◽  
pp. 459-475 ◽  
Keyword(s):  
Mother Cell ◽  
Embryo Sac ◽  
Female Meiosis ◽  
Flower Bud ◽  
Pollen Mother Cells ◽  
Controlled Conditions ◽  
Mean Temperature ◽  
Mother Cells ◽  
Black Beauty

The time and duration of meiosis in ovules and anthers was estimated in plants of two Lilium hybrids (cultivars ‘Sonata’ and ‘Black Beauty’) grown under controlled conditions. Within each flower bud meiosis did not start in the embryo sac mother cell (e.m.c.) until about the time when meiosis in pollen mother cells (p.m.cs) was ended. In both cultivars meiosis lasted about 50% longer in e.m.cs than in p.m.cs. Thus, at a mean temperature of 20 ± 1 °C meiosis in ‘Sonata’ took 7.5 days in p.m.cs and 10.5 days in e.m.cs, while in ‘Black Beauty’ it took 10.5 days in p.m.cs and 16.0 days in e.m.cs.

Relationships among taxa of Elymus (Poaceae: Triticeae) in Australia: reproductive biology

2003 ◽  
Vol 16 (5) ◽  
pp. 633 ◽  
Author(s):  
Michelle A. Murphy
Keyword(s):  
Chromosome Numbers ◽  
Mother Cell ◽  
Megaspore Mother Cell ◽  
Species Complex ◽  
Seed Set ◽  
Embryo Sac ◽  
Mature Embryo ◽  
The Other ◽  
Polymorphic Forms ◽  
Tribe Triticeae

Nomenclatural and taxonomic problems are common among members of the tribe Triticeae and in particular the genus Elymus L. For the Australian representatives of this genus, confusion surrounds the number of taxa present, and which literature belongs to which 'taxon'. The literature indicates at least four major taxa: (1) long-awned forms of E. scaber var. scaber equated to E. rectisetus, (2) shorter-awned forms of E. scaber var. scaber, (3) the very short-awned E. multiflorus and (4) E. scaber var. plurinervis. In addition, a form intermediate between the long- and short-awned forms of E. scaber, as well as populations containing polymorphic forms have been reported. A recent taxonomic treatment of the species complex identified a fifth taxon, E. sp. A. This taxon has previously been identified as E. scaber or E. multiflorus. The current study examined 500 pistils from megaspore mother cell to mature embryo sac, somatic and haploid chromosome numbers, and seed set of nine populations of E. scaber var. scaber sensu lato (common wheatgrass). They included forms equating to E. rectisetus, E. scaber and E. sp. A, a population with intermediate characteristics, and three polymorphic populations. Taxon (1) above is apomictic; taxon (2) contains two entities, one a facultative apomict encompassing the intermediate and polymorphic populations, and the other, the sexual E. sp. A. Exclusive sexuality was also confirmed for material of (3) and (4).

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