scholarly journals Distribution of poly(A)-containing RNA during normal pollen development and during induced pollen embryogenesis in Hyoscyamus niger.

1981 ◽  
Vol 89 (3) ◽  
pp. 593-606 ◽  
Author(s):  
V Raghavan
Keyword(s):  
Transcriptional Activation ◽  
Pollen Grains ◽  
Pollen Embryogenesis ◽  
Vegetative Nucleus ◽  
Generative Nucleus ◽  
Hyoscyamus Niger ◽  
Polyuridylic Acid ◽  
Rna Accumulation ◽  
Rna Formation

The distribution of poly(A)-containing RNA [poly(A)+RNA] in pollen grains of Hyoscyamus niger during normal gametophytic development and embryogenic development induced by culture of anther segments was followed by in situ hybridization with [3H]-polyuridylic acid as a probe. No binding of the isotope occurred in pollen grains during the uninucleate phase of their development. Although [3H]polyuridylic acid binding sites were present in the generative and vegetative cells of maturing pollen grains, they almost completely disappeared from mature grains ready to germinate. During pollen germination, poly(A)+RNA formation was transient and was due to the activity of the generative nucleus, whereas the vegetative nucleus and the sperm cells failed to interact with the applied probe. In cultured anther segments, moderate amounts of poly(A)+RNA were detected in the uninucleate, nonvacuolate, embryogenically determined pollen grains. Poly(A)+RNA accumulation in these grains was sensitive to actinomycin D, suggesting that it represents newly transcribed mRNA. After the first haploid mitosis in the embryogenically determined pollen grains, only those grains in which the generative nucleus alone or along with the vegetative nucleus accumulated poly(A)+RNA in the surrounding cytoplasm were found to divide in the embryogenic pathway. Overall, the results suggest that, in contrast to normal gametophytic development, embryogenic development in the uninucleate pollen grains of cultured anther segments of H. niger is due to the transcriptional activation of an informational type of RNA. Subsequent divisions in the potentially embryogenic binucleate pollen grains appeared to be mediated by the continued synthesis of mRNA either in the generative nucleus or in both the generative and vegetative nuclei.

scholarly journals Microsporogenesis, Macrosporogenesis, and Development of the Macrogametophyte and Seeds of Duboisia Leighhardtii (F.v.M.) and D. Myoporoides (R.Br.)

1949 ◽  
Vol 2 (3) ◽  
pp. 241 ◽  
Author(s):  
C Barnard
Keyword(s):  
Pollen Tube ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Vegetative Nucleus ◽  
Generative Nucleus ◽  
Haploid Number ◽  
Starch Grains ◽  
The Family

In Duboisia Leichhardtii and D. myoporoides macrosporogenesis and the development of the embryo-sac are similar to the descriptions reported for other genera of the family Solanaceae. The haploid number of chromosomes in both species is 30. A generative and vegetative nucleus is formed in each micros pore which later becomes filled with starch grains and uninucleate as a result of degeneration of the vegetative nucleus. At maturity the pollen grains are devoid of starch and are uninucleate. Division of the generative nucleus to form two male nuclei presumably occurs just prior to the discharge of the pollen tube.

scholarly journals 3H-thymidyne incorporation into the microspores and pollen grains nuclei in excised Tradescantia stamens

2015 ◽  
Vol 47 (1–2) ◽  
pp. 163-172 ◽  
Author(s):  
Maria Charzyńska ◽  
Joanna Maleszka
Keyword(s):  
Dna Synthesis ◽  
Generative Cell ◽  
Pollen Grains ◽  
Vegetative Nucleus ◽  
Generative Nucleus ◽  
Tetrad Stage ◽  
Pollen Grain Wall ◽  
Medium Culture

The development of microspores and pollen grains lasts in <i>Tradescantia bracteata in vivo</i> from the tetrad stage to pollen shedding about 14 days. This including 7 days of the microspore life cycle. In stamens excised and placed on a medium the microspores and pollen grains develop normally for at least 3 days. <sup>3</sup>H-thymidine is added into medium culture. DNA synthesis m the microspore nucleus is demonstrated 6 days after tetrad formation so at the end of microspore interphase. During synthesis the nucleus lies at one end of the long axis of the vacuolated microspore. Synthesis ends before migration of the nucleus to the proximal pole of the microspore where mitosis begins. Incorporation of <sup>3</sup>H-thymidine into the generative nucleus is noted in two-celled pollen grains as early as about 24h after the end of microspore division. During DNA synthesis the generative cell is rounded and is still adjacent to the pollen grain wall. DNA synthesis ends before separation of the generative cell from the sporoderm, before the generative nucleus starts to elongate. <sup>3</sup>H-thymidine is not incorporated into the vegetative nucleus in stamens developing <i>in vitro</i>.

Protein synthetic activity during normal pollen development and during induced pollen embryogenesis in Hyoscyamus niger

1984 ◽  
Vol 62 (12) ◽  
pp. 2493-2513 ◽  
Author(s):  
V. Raghavan
Keyword(s):  
Vegetative Cell ◽  
Generative Cell ◽  
Pollen Grains ◽  
Synthetic Activity ◽  
Pollen Embryogenesis ◽  
Starch Accumulation ◽  
Hyoscyamus Niger ◽  
Amino Acid Incorporation ◽  
Pollen Maturation ◽  
Germinating Pollen

Protein synthetic activity during maturation, germination, and embryogenic phases of pollen grains of Hyoscyamus niger (L.) was investigated by means of autoradiography of incorporation of [3H]arginine, [3H]leucine, [3H]lysine, and [3H]tryptophan. Silver grain counts showed that during pollen maturation, peaks of incorporation of [3H]arginine and [3H]lysine occurred before the onset of vacuolation in the uninucleate pollen grains and as starch accumulation was initiated in the bicellular pollen grains. In the latter, labeled amino acids were mostly incorporated into the vegetative cell and very little appeared in the generative cell. [3H]leucine and [3H]tryptophan were not incorporated into uninucleate pollen grains at any stage of their development, although they were localized in the vegetative cell of bicellular pollen grains. In germinating pollen grains the nucleus of the vegetative cell, the generative cell, and sperms did not incorporate the isotopes. While the majority of pollen grains incorporated [3H]arginine, [3H]leucine, [3H]lysine, and [3H]tryptophan immediately after culture of anthers, during further periods of culture, protein synthetic activity persisted only in a small number of uninucleate, nonvacuolate, and densely staining "embryogenically determined" pollen grains confined to the periphery of the anther locule. Subsequent division of these pollen grains was accompanied by incorporation of [3H]arginine, [3H]leucine, and [3H]lysine into the vegetative cell or into both the vegetative cell and generative cell. It is suggested that, in contrast to the 3H-labeled amino acid incorporation pattern observed in pollen grains during their normal ontogeny, a significant change associated with embryogenic induction is the incorporation of [3H]leucine and [3H]tryptophan into embryogenically determined uninucleate pollen grains and of [3H]arginine, [3H]leucine, and [3H]lysine into the generative cell of bicellular pollen grains.

Cytology of exceptional development of the male gametophyte in Ophiorrhiza mungos

1975 ◽  
Vol 53 (18) ◽  
pp. 2032-2037 ◽  
Author(s):  
Omana Philip ◽  
P. M. Mathew
Keyword(s):  
Male Gametophyte ◽  
Pollen Grains ◽  
Nuclear Bodies ◽  
Vegetative Nucleus ◽  
Generative Nucleus ◽  
Sperm Nuclei ◽  
Normal Division

In Ophiorrhiza mungos L. the first division of the microspore nucleus gives rise to a large vegetative nucleus and a smaller generative nucleus. The vegetative nucleus subsequently fragments into a number of irregularly sized particles. These vegetative nuclear bodies move to and flow out of the three germ pores to form three spherical buds on the developing pollen grains. The 'pollen buds' are shed off from the pollen proper before dehiscence. The uninucleate grains readily germinate in vitro, and the single generative nucleus undergoes normal division to give rise to two sperm nuclei.

scholarly journals Tradescantia bracteata pollen in vitro: pollen tubes development and mitosis

2015 ◽  
Vol 46 (4) ◽  
pp. 587-598 ◽  
Author(s):  
E. Lewandowska ◽  
M. Charzyńska
Keyword(s):  
Pollen Tube ◽  
Generative Cell ◽  
Metaphase Plate ◽  
Pollen Grains ◽  
Neutral Red ◽  
Generative Nucleus ◽  
Mitotic Spindles ◽  
Germinating Pollen ◽  
Vacuolar System

About 90 per cent of <i>Tradescantia bracteata</i> pollen germinates <i>in vitro</i> after 15 min. Mitosis starts in the pollen tube after about 3 h. The mitotic trans-formations of chromosomes within the generative nucleus are not synchronized. They involve succesively the linearly arranged chromosomes in the elongated generative nucleus. In metaphase the chromosomes are arranged tandem-like linearly along the pollen tube. The chromatides translocate in anaphase from various distances to the poles in a plane parallel to the metaphase plate. This suggests that chromosomes have individual mitotic spindles and that coordination of the chromosome transformations in the generative cell is much less strict than in a typical somatic mitosis. Starch is the storage material of pollen grains. In the vegetative cytoplasm of mature pollen grains minute reddish-orange vesicular structures are visible after staining with neutral red. They do not fuse with the vacuoles proper arising in germinating pollen grains to form the vacuolar system of the pollen tube.

scholarly journals Growth-regulated expression of rhoG, a new member of the ras homolog gene family.

1992 ◽  
Vol 12 (7) ◽  
pp. 3138-3148 ◽  
Author(s):  
S Vincent ◽  
P Jeanteur ◽  
P Fort
Keyword(s):  
Gene Family ◽  
Transcriptional Activation ◽  
Small Gtpase ◽  
Lung Fibroblasts ◽  
Human Organs ◽  
Regulated Expression ◽  
Genes Encoding ◽  
Rna Stabilization ◽  
Rna Accumulation ◽  
High Level

Cellular transition from the resting state to DNA synthesis involves master switches genes encoding transcriptional factors (e.g., fos, jun, and egr genes), whose targets remain to be fully characterized. To isolate coding sequences specifically accumulated in late G1, a differential screening was performed on a cDNA library prepared from hamster lung fibroblasts stimulated for 5 h with serum. One of the positive clones which displayed a sevenfold induction, turned out to code for a protein sharing homology to Ras-like products. Cloning and sequence analysis of the human homolog revealed that this putative new small GTPase, referred to as rhoG, is more closely related to the rac, CDC42, and TC10 members of the rho (ras homolog) gene family and might have diverged very early during evolution. rhoG mRNA accumulates in proportion to the mitogenic strength of various purified growth factors used for the stimulation, as a consequence of transcriptional activation. G1-specific RNA accumulation is impaired upon addition of antimitogenic cyclic AMP and is enhanced when protein synthesis is inhibited, mainly as a result of RNA stabilization. rhoG mRNA expression is observed in a wide variety of human organs but reaches a particularly high level in lung and placental tissues.

Development of sperm cells in barley

1975 ◽  
Vol 53 (10) ◽  
pp. 1051-1062 ◽  
Author(s):  
David D. Cass ◽  
Ilana Karas
Keyword(s):  
Cell Membrane ◽  
Vegetative Cell ◽  
Generative Cell ◽  
Pollen Grains ◽  
Complete Separation ◽  
Pollen Wall ◽  
Vegetative Nucleus ◽  
Sperm Cells ◽  
Subsequent Stage ◽  
Microspore Stage

Ultrastructural events in barley sperm development were examined from the uninucleate microspore stage to establishment of two mature sperm cells in pollen grains. Microspore mitosis produces a vegetative nucleus and a naked generative cell, both embedded in vegetative cell cytoplasm. The generative cell membrane is enclosed by vegetative cell membrane. The generative cell, at first apparently unattached, becomes attached to the pollen wall and acquires a cell wall by centripetal vesicle accumulation. Wall formation may be complete at the time of generative cell karyokinesis; karyokinesis occurs while the generative cell is attached to the pollen wall. Cytokinesis of the generative cell is delayed. The subsequent stage is a binucleate, attached generative cell with a wall. Generative cell cytokinesis appears to involve formation of a partition between the two sperm nuclei. Eventual complete separation of the sperm cells occurs only after the two-celled derivative of the generative cell detaches from the pollen wall. Final stages in sperm cell separation are considered to result from degradation of the partitioning and surrounding wall, not from furrowing of a naked binucleate generative cell according to previous suggestions. Mature plastids were not observed in the generative cell or the sperms.

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