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.

An ultrastructural study of pollen development in tomato (Lycopersicon esculentum). II. Pollen maturation

1993 ◽  
Vol 71 (8) ◽  
pp. 1048-1055 ◽  
Author(s):  
P. L. Polowick ◽  
V. K. Sawhney
Keyword(s):  
Lycopersicon Esculentum ◽  
Vegetative Cell ◽  
Generative Cell ◽  
Pollen Grains ◽  
Mature Pollen ◽  
Ultrastructural Changes ◽  
Second Phase ◽  
Cell Cytoplasm ◽  
Pollen Maturation

The maturation of tomato pollen grains encompassed several ultrastructural changes. The generative cell separated from the intine and was free in the cytoplasm of the vegetative cell. This process coincided with the appearance of starch in plastids and the division of elongated mitochondria. This stage was followed by a second phase of vacuolation in the vegetative cell cytoplasm. Starch was still abundant at this stage, as were mitochondria, endoplasmic reticulum (ER), and ribosomes. Lipid droplets were the prominent feature of mature pollen grains. Each droplet was surrounded by rough ER (RER), suggesting the role of RER in lipid accumulation and mobilization. Long stretches of ER were present at early stages of maturation, and stacks of up to 50 strands of RER were abundant in mature pollen. The plastids in mature pollen were devoid of starch and had few internal membranes. Mitochondria were abundant and spherical with parallel cristae. In many cases, the cytoplasm at the periphery of the mature pollen grain was dense, forming a distinct zone, and contained only ER. The generative cell cytoplasm had mitochondria, ER, and actin-like filaments but no plastids. The pollen wall at maturity had a lamellated foot layer, a lightly sculptured tectum, and broad intine. The intine was layered in the region of the pollen aperture. Key words: Lycopersicon esculentum, pollen grains, tomato, ultrastructure.

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.

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.

Elektronenmikroskopische Beobachtungen an der vegetativen Zelle im auskeimenden Pollenkorn von Oenothera hookeri Torr. et Grey

1963 ◽  
Vol 18 (12) ◽  
pp. 1092-1097 ◽  
Author(s):  
Lothar Diers
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Nuclear Envelope ◽  
Vegetative Cell ◽  
Generative Cell ◽  
Pollen Grain ◽  
Serial Sections ◽  
Lipid Inclusions ◽  
Intense Activity ◽  
Germinating Pollen

According to the intense activity of the vegetative cell in the germinating pollen grain, the cytoplasm shows a highly organized structure. Concerning the structure the vegetative cell differs strongly from the generative cell. In the vegetative cell the big nucleus shows a very lobed shape. Large invaginations of the cytoplasm into the nucleus can be frequently observed. Series of adjacent sections show that deep and flat vesicles which may often broaden to unusual large cisternae, extend through the vegetative plasm and form by interconnections a highly developed endoplasmic reticulum which is continuous with the nuclear envelope. The leucoplasts contain large starch grains and very few lamellae, in many sections only one lamella is visible. Sometimes, a process of a leucoplast deeply reaches into another leucoplast. In some leucoplasts and mitochondria there are concentric stripes which, according to serial sections, are the margins of invaginations of the cytoplasm or of another organell. In the numerous mitochondria the inner folds have the form of cristae, tubules are not so frequently seen. The edges of the flattened sacs of the Golgi - apparatus expand to vacuoles which seem to separate from the flattened cisternae. Typical for the vegetative plasm are numerous small vacuoles. Relatively large, ringshaped or uniform dark bodies are assumed to be lipid inclusions.

scholarly journals An L-type lectin receptor-like kinase promotes starch accumulation during rice pollen maturation

Development ◽  
2021 ◽  
pp. dev.196378
Author(s):  
Zhiyuan He ◽  
Ting Zou ◽  
Qiao Xiao ◽  
Guoqiang Yuan ◽  
Miaomiao Liu ◽  
...  
Keyword(s):  
Starch Synthesis ◽  
Pollen Grains ◽  
Starch Accumulation ◽  
Male Sterile ◽  
Pollen Maturation ◽  
Lectin Receptor ◽  
Rice Mutant ◽  
Receptor Like Kinase ◽  
Mutant Pollen

Starch accumulation is key for the maturity of rice pollen grains; however, the regulatory mechanism underlying this process remains unknown. Here, we isolated a male-sterile rice mutant, abnormal pollen 1 (ap1), which produces nonviable pollen grains with defective starch accumulation. Functional analysis revealed that AP1 encodes an active L-type lectin receptor-like kinase (L-LecRLK). AP1 is localized to the plasma membrane and its transcript is highly accumulated in pollen during the starch synthesis phase. RNA-seq and phosphoproteomic analysis revealed that the expression/phosphorylation levels of numerous genes/proteins involved in starch and sucrose metabolism pathway were significantly altered in the mutant pollen, including a known rice UDP-glucose pyrophosphorylase (OsUGP2). We further found that AP1 physically interacts with OsUGP2 to elevate its enzymatic activity likely through targeted phosphorylation. These findings revealed a novel role of L-LecRLK in controlling pollen maturity via modulating sucrose and starch metabolism.

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.

Cytokinin effects on pollen embryogenesis in cultured anthers of Hyoscyamus niger

1989 ◽  
Vol 67 (1) ◽  
pp. 247-257 ◽  
Author(s):  
V. Raghavan ◽  
R. Nagmani
Keyword(s):  
Callus Formation ◽  
Generative Cell ◽  
Basal Medium ◽  
Root Apex ◽  
Zeatin Riboside ◽  
Pollen Embryogenesis ◽  
Zygotic Embryogenesis ◽  
Hyoscyamus Niger ◽  
Mineral Salts ◽  
Isopentenyl Adenine

Addition of the cytokinins, benzylaminopurine, N6-Δ-(2-isopentenyl)-adenine, kinetin, zeatin, and zeatin riboside to a basal medium containing mineral salts and sucrose induced characteristic changes in pollen embryogenesis in cultured anthers and anther segments of Hyoscyamus niger. In anthers cultured in media containing 0.01–10.0 mg/L of each cytokinin, there was a progressive delay in the appearance of plantlets outside the anther locule and in the morphology of plantlets formed. Among the cytokinins tested, only zeatin riboside promoted anther efficiency; however, all compounds reduced pollen efficiency by as much as 40–60% of the control even in the lowest concentration tested. The effects of cytokinins were particularly noticeable in the failure of pollen grains to form embryoids by the division of the generative cell and in the decrease in the number of embryoids formed by the division of both generative and vegetative cells. At the morphogenetic level, embryoids formed in media containing cytokinins displayed various abnormalities such as precocious elongation of the root apex, cotyledon expansion, and callus formation on the cotyledons, hypocotyl, and root. During their subsequent growth, calluses induced on embryoids by benzylaminopurine, N6-Δ-(2-isopentenyl)-adenine, zeatin, and zeatin riboside formed somatic embryos that recapitulated stages of zygotic embryogenesis. Globular and heart-shaped embryoids, which did not develop further, were frequently observed on kinetin-induced pollen callus; the callus also regenerated leafy shoots by organogenesis. Addition of adenine to the medium did not have any effect on pollen embryogenesis in cultured anthers of H. niger.

scholarly journals Intracellular motility and the evolution of the actin cytoskeleton during development of the male gametophyte of wheat ( Triticum aestivum L.)

1997 ◽  
Vol 352 (1364) ◽  
pp. 1985-1993 ◽  
Author(s):  
J. Heslop-Harrison ◽  
Y. Heslop-Harrison
Keyword(s):  
Actin Cytoskeleton ◽  
Vegetative Cell ◽  
Male Gametophyte ◽  
Generative Cell ◽  
Triticum Aestivum L ◽  
Starch Accumulation ◽  
Vegetative Nucleus ◽  
Published Evidence ◽  
Main Period ◽  
Actin Mrna

The uniaperturate pollen of wheat is dispersed in a partially hydrated condition. Amyloplasts are concentrated in the apertural hemisphere where they surround the two sperms, while vigorously moving polysaccharide–containing wall precursor bodies (P–particles) together with the vegetative nucleus occupy the other. This disposition is the product of a post–meiotic developmental sequence apparently peculiar to the grasses. During vacuolation of the spore after release from the tetrad, the nucleus is displaced to the pole of the cell opposite the site of the germination aperture, already defined in the tetrad. Following pollen mitosis, the vegetative nucleus migrates along the wall of the vegetative cell towards the aperture, leaving the generative cell at the opposite pole isolated by a callose wall. As the vacuole is resorbed, the generative cell rounds up, loses its wall and follows the vegetative nucleus, passing along the wall of the vegetative cell towards the aperture where it eventually divides to produce the two sperms. Throughout this period of nucleus and cell manoeuvrings, minor inclusions of the vegetative cell cytoplasm, including mitochondria, lipid globuli and developing amyloplasts, move randomly. Coordinated vectorial movement begins after the main period of starch accumulation, when the amyloplasts migrate individually into the apertural hemisphere of the grain, a final redistribution betokening the attainment of germinability. In the present paper we correlate aspects of the evolution of the actin cytoskeleton with these events in the developing grain, and relate the observations to published evidence from another monocotyledonous species concerning the timing of the expression of actin genes during male gametophyte development, as revealed in the synthesis of actin mRNA.

scholarly journals Ultrastructural and metabolic transformations of differentiating Hyacinthus orientalis L, pollen grain cells. I. RNA and protein synthesis

2014 ◽  
Vol 53 (2) ◽  
pp. 145-158 ◽  
Author(s):  
Elżbieta Bednarska
Keyword(s):  
Protein Synthesis ◽  
Vegetative Cell ◽  
Generative Cell ◽  
Growth Dynamics ◽  
Pollen Grains ◽  
Pollen Grain ◽  
Cell Protein ◽  
Replication Process ◽  
Rna And Protein Synthesis ◽  
Hyacinthus Orientalis

RNA and protein synthesis were investigated in generative and vegetative cells during maturation of pollen grains. The rate of RNA and protein synthesis was analysed in reference to the successive interphase periods of the life cycle of pollen cells as well as against the background of the growth dynamics of the cell volume. The results of studies demonstrated that the pollen grain increases in size owing to the growth of the vegetative cell. The generative one does not grow. RNA synthesis and that of proteins in differentiating pollen cells has a different course. In the growing vegetative cell it lasts longer and is more intensive than in the generative cell which does not grow. RNA and protein synthesis in the vegetative cell take place in the period from the callose stage to the stage of lemon-shaped generative cell, that is in the period of phases G<sub>1</sub>, S and G<sub>2</sub>. This synthesis is positively correlated with the growth of the pollen grain. RNA and protein synthesis in the generative cell comprises the period from the callose-less lenticular stage to the stage of spherical generative cell, that is the phases S and early phase G<sub>2</sub>. These results suggest that in the vegetative cell RNA and protein synthesis is utilised above all to increase of its cell, instead in non growing generative cell protein synthese is probably limited mostly to a histones and enzymatic proteins serving for the DNA replication process.

Fine Structure Study of Pollen Development in Haemanthus katherinae Baker

1971 ◽  
Vol 8 (2) ◽  
pp. 289-301
Author(s):  
JEAN M. SANGER ◽  
W. T. JACKSON
Keyword(s):  
Fine Structure ◽  
Vegetative Cell ◽  
Daughter Nucleus ◽  
Generative Cell ◽  
Pollen Grains ◽  
Cell Plate ◽  
Structure Study ◽  
Pollen Grain ◽  
Pollen Wall ◽  
Fibrillar Material

When microspores of the African blood lily divide, they form pollen grains which consist of 2 cells of unequal size. This is accomplished when the microspore nucleus is displaced from the centre of the grain prior to division. The displacement is always towards the side of the grain opposite the furrow, and large vacuoles form in the cytoplasm between the furrow and the nucleus. During cell division the cell plate curves around one daughter nucleus and fuses with the pollen wall to enclose the generative cell. The cell-plate attachment always occurs with the wall that is opposite the furrow of the grain. Most of the microspore's organelles become incorporated in the larger vegetative cell, whereas the generative cell has few, if any, plastids and only a small number of other organelles. The wall around the generative cell is composed of finely fibrillar material enclosed within 2 unit membranes. The generative cell eventually becomes detached from the pollen wall, becomes spheroidal, and moves to a position near the centre of the pollen grain. At the same time, the large vacuoles disappear from the vegetative cell and the number of organelles increases substantially.

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