The Significance of Microspore Division and Division Symmetry for Vegetative Cell-Specific Transcription and Generative Cell Differentiation

1995 ◽  
Vol 7 (1) ◽  
pp. 65 ◽  
Author(s):  
Colin Eady ◽  
Keith Lindsey ◽  
David Twell
Keyword(s):  
Cell Differentiation ◽  
Vegetative Cell ◽  
Generative Cell

scholarly journals Proteomic Analysis of Generative and Vegetative Nuclei Reveals Molecular Characteristics of Pollen Cell Differentiation in Lily

2021 ◽  
Vol 12 ◽  
Author(s):  
Chen You ◽  
YuPing Zhang ◽  
ShaoYu Yang ◽  
Xu Wang ◽  
Wen Yao ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
Pollen Tube ◽  
Cell Fate ◽  
Vegetative Cell ◽  
Generative Cell ◽  
Histone Variants ◽  
Molecular Characteristics ◽  
Nuclear Pore ◽  
Cell Nuclei ◽  
Pollen Cell

In plants, the cell fates of a vegetative cell (VC) and generative cell (GC) are determined after the asymmetric division of the haploid microspore. The VC exits the cell cycle and grows a pollen tube, while the GC undergoes further mitosis to produce two sperm cells for double fertilization. However, our understanding of the mechanisms underlying their fate differentiation remains limited. One major advantage of the nuclear proteome analysis is that it is the only method currently able to uncover the systemic differences between VC and GC due to GC being engulfed within the cytoplasm of VC, limiting the use of transcriptome. Here, we obtained pure preparations of the vegetative cell nuclei (VNs) and generative cell nuclei (GNs) from germinating lily pollens. Utilizing these high-purity VNs and GNs, we compared the differential nucleoproteins between them using state-of-the-art quantitative proteomic techniques. We identified 720 different amount proteins (DAPs) and grouped the results in 11 fate differentiation categories. Among them, we identified 29 transcription factors (TFs) and 10 cell fate determinants. Significant differences were found in the molecular activities of vegetative and reproductive nuclei. The TFs in VN mainly participate in pollen tube development. In comparison, the TFs in GN are mainly involved in cell differentiation and male gametogenesis. The identified novel TFs may play an important role in cell fate differentiation. Our data also indicate differences in nuclear pore complexes and epigenetic modifications: more nucleoporins synthesized in VN; more histone variants and chaperones; and structural maintenance of chromosome (SMC) proteins, chromatin remodelers, and DNA methylation-related proteins expressed in GN. The VC has active macromolecular metabolism and mRNA processing, while GC has active nucleic acid metabolism and translation. Moreover, the members of unfolded protein response (UPR) and programmed cell death accumulate in VN, and DNA damage repair is active in GN. Differences in the stress response of DAPs in VN vs. GN were also found. This study provides a further understanding of pollen cell differentiation mechanisms and also a sound basis for future studies of the molecular mechanisms behind cell fate differentiation.

scholarly journals Autoradiographic studies of DNA and histone synthesis in successive differentiation stages of pollen grain in Hyacinthus orientalis L.

2014 ◽  
Vol 50 (3) ◽  
pp. 367-380 ◽  
Author(s):  
Elżbieta Bednarska
Keyword(s):  
Dna Replication ◽  
Dna Synthesis ◽  
Vegetative Cell ◽  
Developmental Stages ◽  
Generative Cell ◽  
Pollen Grain ◽  
Cell Nuclei ◽  
Hyacinthus Orientalis ◽  
Histone Synthesis ◽  
Generative Cells

DNA and histone synthesis in five consecutive morphological stages of <em>Hyacinthus orientalis</em> L. pollen grain differentiation were studied autoradiographically. DNA synthesis was found to occur in both the generative and the vegetative cell. DNA replication in the generative cell took place when the generative cell was still adhered to the pollen grain wall but already devoid of callose wall. DNA synthesis in the generative cell slightly preceded that in the vegetative cell. Histones were synthesized in phase S of the generative and vegetative cell. In the generative cell histone synthesis also continued at a lower level after completion of DNA replication. In the developmental stages under study the nuclei of the generative cells were decidedly richer in lysine histones than vegetative cell nuclei.

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.

scholarly journals Ultrastructural study of maturing pollen in Arabidopsis thaliana (L.) Heynh. (Brassicaceae)

2014 ◽  
Vol 66 (2) ◽  
pp. 125-131 ◽  
Author(s):  
Krystyna Zając
Keyword(s):  
Arabidopsis Thaliana ◽  
Vegetative Cell ◽  
Generative Cell ◽  
Spherical Shape ◽  
Ultrastructural Changes ◽  
Lipid Bodies ◽  
Cell Cytoplasm ◽  
Cell Form ◽  
Microspore Stage ◽  
Pollen Stage

Ultrastructural changes in <em>Arabidopsis thaliana</em> pollen, between late microspore stage and mature pollen stage were described. When the generative cell was peeled off from the intine, it was of spherical shape and had all usual organelles with the exception of plastids. The cytoplasm transformation of the vegetative cell included an increase in the number of mitochondria and changes in the accumulation of starch and lipid bodies. The starch plastids were observed at the bicellular and early tricellular pollen stages and next starch was utilized during the maturation procces. The lipid bodies of the vegetative cell form a very regular sheath around the generative cell and then, around the sperm cells. Before anthesis the lipid bodies were dispersed within the whole vegetative cell cytoplasm.

scholarly journals Ultrastructural transformations in the cytoplasm of differentiating Hyacinthus orientalis L. pollen cells

2014 ◽  
Vol 57 (2) ◽  
pp. 235-245 ◽  
Author(s):  
Elżbieta Bednarska
Keyword(s):  
Vegetative Cell ◽  
Generative Cell ◽  
Pollen Grain ◽  
Border Region ◽  
Ultrastructural Changes ◽  
Grain Development ◽  
Callose Wall ◽  
Highly Active ◽  
Hyacinthus Orientalis

The sequence of ultrastructural changes in the cytoplasm during the successive stages of pollen grain development in <em>Hyacinthus orientulis</em> pollen cells was studied. The cytoplasmic transformations of the generative cell included the elimination of plastids, increase in the number of mitochondria, assumption of a spindle shape with the aid of microtubules and the characteristic development of the vacuole system with the formation of so-called colored bodies. The cytoplasmic transformations of the generative cell encompassed changes in the plastids, which began to accumulate starch soon after the cell was formed, then released it shortly before anthesis, an increase in the number of mitochondria and an increase in the number of highly active dictyosomes just before anthesis. Changes in the structure of the border region between the differentiating pollen cells were associated mainly with the periodical appearance of a callose wall and the presence of lysosome-like bodies in the cytoplasm of the vegetative cell surrounding the generative cell. They arose soon after the disappearance of the callose wall and disappeared shortly before anthesis.

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.

The Ultrastructure and Ontogeny of Pollen in Helleborus Foetidus L

1972 ◽  
Vol 11 (1) ◽  
pp. 111-129
Author(s):  
P. ECHLIN
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Vegetative Cell ◽  
Generative Cell ◽  
Ultrastructural Level ◽  
Mitotic Division ◽  
Tube Formation ◽  
Pollen Grain ◽  
Granular Body ◽  
Development Proceeds

The final stages of Helleborus pollen-grain ontogeny, which culminate in maturation and germination of the grain, have been investigated at the ultrastructural level. Following the deposition of primary and secondary exine, and during the early stages of intine formation, the microspore passes through a vacuolate phase, in which the cytoplasm appears devoid of most organelles other than the prominent nucleus. The formation of the vacuole results in the displacement of the nucleus to one side of the pollen grain. The vacuole quickly disappears and a number of organelles reappear in the cytoplasm, in particular the dictyosomes and strands of endoplasmic reticulum, with associated grey bodies. Following mitotic division of the pollen grain, the first signs of the generative cell wall appear as a pair of tightly appressed unit membranes in the narrow strand of cytoplasm separating the two newly formed generative and vegetative nuclei. As development proceeds, the space between the two membranes gradually fills with an electron-transparent material similar to the substance found in the numerous dictyosome-derived vesicles which, together with the endoplasmic reticulum, are both closely associated with the developing cell wall. The generative cell wall fuses with the cellulosic intine, which has gradually increased in amount during these stages, and the cell division is complete. The smaller generative cell contains a prominent nucleus and a small amount of cytoplasm devoid of plastids and most other organelles. The larger vegetative cell also contains a prominent nucleus and a large amount of cytoplasm containing amyloplasts, mitochondria, dictyosomes and endoplasmic reticulum, and abundant ribosomes, many of which are in a polysome configuration. The final stages in development are characterized by a progressive decrease in the amount of starch in the vegetative cell and an increase in the size of grey bodies, many of which are invested in multilayered shrouds of endoplasmic reticulum. The generative cell wall disappears and a multivesicular/granular body gradually appears at the periphery of the pollen grain. The granular-vesicular material, which is formed from the dictyosomes and/or the degenerating plastids, is thought to represent metabolic reserves necessary for pollen-tube formation. One or more pollen tubes emerge from the apertural sectors of the pollen grain, and maturation of the grain is complete.

sidecar pollen, an Arabidopsis thaliana male gametophytic mutant with aberrant cell divisions during pollen development

Development ◽  
1996 ◽  
Vol 122 (10) ◽  
pp. 3243-3253 ◽  
Author(s):  
Y.C. Chen ◽  
S. McCormick
Keyword(s):  
Pollen Development ◽  
Vegetative Cell ◽  
Generative Cell ◽  
Wild Type ◽  
Cell Divisions ◽  
Division Pattern ◽  
Pollen Plants ◽  
Microspore Mitosis ◽  
Pollen Tetrad ◽  
Asymmetric Mitosis

During pollen development each product of meiosis undergoes a stereotypical pattern of cell divisions to give rise to a three-celled gametophyte, the pollen grain. First an asymmetric mitosis generates a larger vegetative cell and a smaller generative cell, then the generative cell undergoes a second mitosis to give rise to two sperm cells. It is unknown how this pattern of cell divisions is controlled. We have identified an Arabidopsis gene, SIDECAR POLLEN, which is required for the normal cell division pattern during pollen development. In the genetic background of the NoO ecotype, sidecar pollen heterozygotes have about 45% wild-type pollen, 48% aborted pollen and 7% pollen with an extra cell. Homozygous sidecar pollen plants have about 20% wild-type pollen, 53% aborted pollen and 27% extra-celled pollen. Similar ratios of sidecar pollen phenotypes are seen in the Columbia ecotype but sidecar pollen is a gametophytic lethal in the Landsberg erecta ecotype. Thus this allele of sidecar pollen shows differential gametophytic penetrance and variable expressivity in different genetic backgrounds. The extra cell has the cell identity of a vegetative cell and is produced prior to any asymmetric microspore mitosis. Pollen tetrad analysis directly demonstrates that SIDECAR POLLEN is indeed expressed in male gametophytes. To our knowledge, scp is the first male gametophytic mutation to be described in Arabidopsis.

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