DIPLOPHASE ACTIVITY OF STEMONITIS FUSCA ROTH

1963 ◽  
Vol 41 (12) ◽  
pp. 1639-1643 ◽  
Author(s):  
W. G. Benedict
Keyword(s):  
Life Cycle ◽  
Nuclear Division ◽  
Diploid Cell

The diploid swarm cell in the life cycle of Stemonitis fusca was observed continuously following syngamy through encystment and a nuclear division to the formation of other swarmcells. Evidence is presented to show that the first diploid cell may not be the primary plasmodial cell under certain microcultural conditions.

Biosynthesis of Collagen during the Life Cycle of Human Diploid Cell Lines

1975 ◽  
pp. 339-350 ◽  
Author(s):  
J. Hurych ◽  
M. Macek ◽  
K. Smetana ◽  
F. Beniač ◽  
D. Řezáčová
Keyword(s):  
Life Cycle ◽  
Cell Lines ◽  
Diploid Cell ◽  
Human Diploid Cell

Colletotrichum lindemuthianum exhibits different patterns of nuclear division at different stages in its vegetative life cycle

Mycologia ◽  
2013 ◽  
Vol 105 (4) ◽  
pp. 795-801 ◽  
Author(s):  
Francine H. Ishikawa ◽  
Elaine A. Souza ◽  
Nick D. Read ◽  
M. Gabriela Roca
Keyword(s):  
Life Cycle ◽  
Nuclear Division ◽  
Colletotrichum Lindemuthianum

Mitosis and nuclear degeneration: simultaneous events during secondary sporangia formation in Phytophthora palmivora

1973 ◽  
Vol 51 (9) ◽  
pp. 1673-1675 ◽  
Author(s):  
Don E. Hemmes ◽  
Hans R. Hohl
Keyword(s):  
Life Cycle ◽  
Nuclear Division ◽  
Phytophthora Palmivora ◽  
Nuclear Degeneration ◽  
Membranous Material

Somatic nuclear division is described for sporangia of Phytophthora palmivora. The division is intranuclear and involves centrioles and an eccentrically located spindle. The nucleolus persists throughout division. While these events take place, other nuclei within the same sporangium become surrounded by membranous material and degenerate by an autophagous process. The possible significance of these events for this stage of the life cycle is discussed.

scholarly journals Nuclear Division and the Life Cycle in a Streptomyces sp.

1954 ◽  
Vol 11 (1) ◽  
pp. 52-56 ◽  
Author(s):  
J. F. Mcgregor
Keyword(s):  
Life Cycle ◽  
Nuclear Division ◽  
Streptomyces Sp

CYTOLOGY OF THE AECIOSPORES AND AECIOSPORE GERM TUBES OF PERIDERMIUM HARKNESSII AND P. STALACTIFORME OF THE CRONARTIUM COLEOSPORIOIDES COMPLEX

1966 ◽  
Vol 44 (12) ◽  
pp. 1639-1643 ◽  
Author(s):  
Y. Hiratsuka ◽  
W. Morf ◽  
J. M. Powell
Keyword(s):  
Life Cycle ◽  
Germ Tube ◽  
Nuclear Division ◽  
Nuclear Fusion ◽  
Septum Formation ◽  
Germ Tubes

Cytology of aeciospores and aeciospore germ tubes of two pine rusts, Peridermium harknessii J. P. Moore and P. stalactiforme Arth. & Kern, was compared. In P. harknessii the mycelial cells giving rise to aecia were uninucleate. Young aeciospores were usually binucleate but most of them became uninucleate during maturation. Upon germination, nuclear division and septum formation occurred and germ tubes were divided into two, three, or four cells, each of which usually contained one nucleus. One to three side branches developed and nuclei migrated into them. Basidiospores were not produced. Despite the absence of basidiospores, P. harknessii is interpreted as having an endo-type life cycle with nuclear fusion and meiosis. In P. stalactiforme, aeciospores were binucleate and, upon germination, two nuclei migrated into the germ tube. The nuclei remained undivided during the formation of appressoria and infection pegs. Septa were not observed and branching was dichotomous or irregular.

scholarly journals SSP1, a gene necessary for proper completion of meiotic divisions and spore formation in Saccharomyces cerevisiae.

1997 ◽  
Vol 17 (12) ◽  
pp. 7029-7039 ◽  
Author(s):  
D K Nag ◽  
M P Koonce ◽  
J Axelrod
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Chromosome Segregation ◽  
Meiotic Recombination ◽  
Nuclear Division ◽  
Diploid Cell ◽  
Spore Formation ◽  
Yeast Saccharomyces Cerevisiae ◽  
Expression Of Genes ◽  
Diploid Cells ◽  
Differential Expression Of Genes

During meiosis, a diploid cell undergoes two rounds of nuclear division following one round of DNA replication to produce four haploid gametes. In yeast, haploid meiotic products are packaged into spores. To gain new insights into meiotic development and spore formation, we followed differential expression of genes in meiotic versus vegetatively growing cells in the yeast Saccharomyces cerevisiae. Our results indicate that there are at least five different classes of transcripts representing genes expressed at different stages of the sporulation program. Here we describe one of these differentially expressed genes, SSP1, which plays an essential role in meiosis and spore formation. SSP1 is expressed midway through meiosis, and homozygous ssp1 diploid cells fail to sporulate. In the ssp1 mutant, meiotic recombination is normal but viability declines rapidly. Both meiotic divisions occur at the normal time; however, the fraction of cells completing meiosis is significantly reduced, and nuclei become fragmented soon after meiosis II. The ssp1 defect does not appear to be related to a microtubule-cytoskeletal-dependent event and is independent of two rounds of chromosome segregation. The data suggest that Ssp1 is likely to function in a pathway that controls meiotic nuclear divisions and coordinates meiosis and spore formation.

scholarly journals CHROMOSOMAL ALTERNATION OF GENERATIONS IN NEREOCYSTIS LUETKEANA (MERTENS) POSTELS AND RUPRECHT

1961 ◽  
Vol 39 (7) ◽  
pp. 1711-1724 ◽  
Author(s):  
Lindley Kemp ◽  
Kathleen Cole
Keyword(s):  
Life History ◽  
Life Cycle ◽  
Nuclear Division ◽  
Basal Cells ◽  
Cytological Examination ◽  
Male And Female ◽  
Nereocystis Luetkeana ◽  
History Of ◽  
Alternation Of Generations

A cytological examination of the life history of Nereocystis luetkeana has shown that an alternating chromosome number corresponds to the morphological alternation of generations. The first division sequence of the zoosporangial nucleus is meiotic and is followed by three, usually synchronous, mitotic divisions. Thirty-two zoospores are liberated from each sporangium, and their germination gives rise to male and female gametophytes. Genotypic determination of the sexes is believed to take place in Nereocystis. Mitosis in the gametophytes is regular and cytokinesis follows each nuclear division, producing few cells in the female and many cells in the male gametophytes. Thirty-one chromosomes can be counted at the mitotic prophase. Oogamy exists in Nereocystis and fertilization takes place after the egg is extruded from the oogonium. Nuclear division in the sporophyte appears to be preceded by division of the nucleolus. Colorless and non-septate rhizoids develop as elongations of the basal cells of the sporophyte.Temperature is an important factor in the development of various stages of the life cycle of Nereocystis grown in culture, particularly in the gametophytic stage where sexual structures are produced only at temperatures less than 10 °C and vegetative growth is most prolific at 14–18 °C.Some of the unfertilized eggs develop parthenogenetically and give rise to stunted, deformed plants with multinucleate cells.

scholarly journals Genetic transformation of Spizellomyces punctatus, a resource for studying chytrid biology and evolutionary cell biology

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Edgar M Medina ◽  
Kristyn A Robinson ◽  
Kimberly Bellingham-Johnstun ◽  
Giuseppe Ianiri ◽  
Caroline Laplante ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Wall ◽  
Cell Migration ◽  
Life Cycle ◽  
Cell Biology ◽  
Nuclear Division ◽  
Animal Cells ◽  
Animal Evolution ◽  
Transgenic Lines ◽  
A Cell

Chytrids are early-diverging fungi that share features with animals that have been lost in most other fungi. They hold promise as a system to study fungal and animal evolution, but we lack genetic tools for hypothesis testing. Here, we generated transgenic lines of the chytrid Spizellomyces punctatus, and used fluorescence microscopy to explore chytrid cell biology and development during its life cycle. We show that the chytrid undergoes multiple rounds of synchronous nuclear division, followed by cellularization, to create and release many daughter ‘zoospores’. The zoospores, akin to animal cells, crawl using actin-mediated cell migration. After forming a cell wall, polymerized actin reorganizes into fungal-like cortical patches and cables that extend into hyphal-like structures. Actin perinuclear shells form each cell cycle and polygonal territories emerge during cellularization. This work makes Spizellomyces a genetically tractable model for comparative cell biology and understanding the evolution of fungi and early eukaryotes.

scholarly journals Saccharomyces spores are born prepolarized to outgrow away from spore-spore connections and penetrate the ascus wall

2020 ◽  
Author(s):  
Lydia R. Heasley ◽  
Emily Singer ◽  
Michael A. McMurray
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Wall ◽  
Life Cycle ◽  
Fission Yeast ◽  
Site Selection ◽  
De Novo ◽  
Diploid Cell ◽  
Break Symmetry ◽  
Local Cell ◽  
Bud Site

1.AbstractHow non-spore haploid Saccharomyces cells choose sites of budding and polarize towards pheromone signals in order to mate has been a subject of intense study. Unlike non-spore haploids, sibling spores produced via meiosis and sporulation by a diploid cell are physically interconnected and encased in a sac derived from the old cell wall of the diploid, called the ascus. Non-spore haploids bud adjacent to previous sites of budding, relying on stable cortical landmarks laid down during prior divisions, but since spore membranes are made de novo it was assumed that, as is known for fission yeast, Saccharomyces spores break symmetry and polarize at random locations. Here we show that this assumption is incorrect: Saccharomyces cerevisiae spores are born prepolarized to outgrow, prior to budding or mating, away from interspore bridges. Consequently, when spores bud within an intact ascus, their buds locally penetrate the ascus wall, and when they mate, the resulting zygotes adopt a unique morphology reflective of re-polarization towards pheromone, which we dub the derrière. Long-lived cortical foci containing the septin Cdc10 mark polarity sites, but the canonical bud site selection program is dispensable for spore polarity, thus the origin and molecular composition of these landmarks remain unknown. These findings demand further investigation of previously overlooked mechanisms of polarity establishment and local cell wall digestion, and highlight how a key step in the Saccharomyces life cycle has been historically neglected.

Some observations on the life history of Podocarpus falcatus

1960 ◽  
Vol 8 (3) ◽  
pp. 243 ◽  
Author(s):  
TGB Osborn
Keyword(s):  
Life History ◽  
Life Cycle ◽  
Pollen Tube ◽  
Mother Cell ◽  
Nuclear Division ◽  
Embryonic Cells ◽  
Linear Tetrad ◽  
Zygote Nucleus ◽  
Layer Membrane ◽  
History Of

Podocarpus falcatus (R.Br. ex Mirb.) belongs to the 1-year life cycle type of podocarp. Ripe seeds are shed 12–13 months after pollination. There is a single gynospore mother cell in a well-defined tapetum, and the inner spore of a linear tetrad is functional. Pollen tubes make contact with the developing female prothallus before the stage of free nuclear division is complete. They continue to grow downwards between it and the nucellus. There are several superficial archegonia, some of which may be enveloped by a common jacket layer. They are of intermediate length, and develop along the line of contact between the pollen tube and prothallus. The gynospore layer membrane remains thin at this point. Five free mitoses of the zygote nucleus take place, the first two in the mid archegonial area. The proembryonic nuclei become tiered with a low number in the embryonic layer. The embryonic cells have the usual binucleate phase followed by tetrad formation. Simple polyembryony is common, and though fission may occur it is not general.

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