scholarly journals Affinity, life cycle, and intracellular complexity of organic-walled microfossils from the Mesoproterozoic of Shanxi, China

2015 ◽  
Vol 89 (1) ◽  
pp. 28-50 ◽  
Author(s):  
Heda Agić ◽  
Małgorzata Moczydłowska ◽  
Lei-Ming Yin
Keyword(s):  
Cell Wall ◽  
Life Cycle ◽  
Structural Complexity ◽  
Protective Role ◽  
Life Cycles ◽  
Wall Structure ◽  
Phenotypic Characters ◽  
Biological Affinity ◽  
New Material ◽  
A Cell

AbstractLight microscope and scanning electron microscope observations on new material of unicellular microfossilsDictyosphaera macroreticulataandShuiyousphaeridium macroreticulatum,from the Mesoproterozoic Ruyang Group in China, provide insights into the microorganisms’ biological affinity, life cycle and cellular complexity.Gigantosphaeridium fibratumn. gen. et sp., is described and is one of the largest Mesoproterozoic microfossils recorded. Phenotypic characters of vesicle ornamentation and excystment structures, properties of resistance and cell wall structure inDictyosphaeraandShuiyousphaeridiumare all diagnostic of microalgal cysts. The wide size ranges of the various morphotypes indicate growth phases compatible with the development of reproductive cysts. Conspecific biologically, each morphotype represents an asexual (resting cyst) or sexual (zygotic cyst) stage in the life cycle, respectively. We reconstruct this hypothetical life cycle and infer that the organism demonstrates a reproductive strategy of alternation of heteromorphic generations. Similarly inGigantosphaeridium,a metabolically expensive vesicle with processes suggests its protective role as a zygotic cyst. In combination with all these characters and from the resemblance to extant green algae, we propose the placement of these ancient microorganisms in the stem group of Chloroplastida (Viridiplantae). A cell wall composed of primary and secondary layers inDictyosphaeraandShuiyouisphaeridiumrequired a high cellular complexity for their synthesis and the presence of an endomembrane system and the Golgi apparatus. The plastid was also present, accepting the organism was photosynthetic. The biota reveals a high degree of morphological and cell structural complexity, and provides an insight into ongoing eukaryotic evolution and the development of complex life cycles with sexual reproduction by 1200 Ma.

scholarly journals The Root Cap Cuticle: A Cell Wall Structure for Seedling Establishment and Lateral Root Formation

Cell ◽  
2019 ◽  
Vol 176 (6) ◽  
pp. 1367-1378.e8 ◽  
Author(s):  
Alice Berhin ◽  
Damien de Bellis ◽  
Rochus B. Franke ◽  
Rafael A. Buono ◽  
Moritz K. Nowack ◽  
...  
Keyword(s):  
Cell Wall ◽  
Seedling Establishment ◽  
Lateral Root ◽  
Root Formation ◽  
Root Cap ◽  
Cell Wall Structure ◽  
Wall Structure ◽  
Lateral Root Formation ◽  
A Cell

scholarly journals Critical Roles for Lipomannan and Lipoarabinomannan in Cell Wall Integrity of Mycobacteria and Pathogenesis of Tuberculosis

mBio ◽  
2013 ◽  
Vol 4 (1) ◽  
Author(s):  
Takeshi Fukuda ◽  
Takayuki Matsumura ◽  
Manabu Ato ◽  
Maho Hamasaki ◽  
Yukiko Nishiuchi ◽  
...  
Keyword(s):  
Cell Wall ◽  
Mycobacterium Tuberculosis ◽  
Critical Role ◽  
Protective Role ◽  
Cell Wall Integrity ◽  
Structural Defects ◽  
Wall Structure ◽  
Content Type ◽  
Mycobacterial Cell ◽  
Mycobacterial Cell Wall

ABSTRACTLipomannan (LM) and lipoarabinomannan (LAM) are mycobacterial glycolipids containing a long mannose polymer. While they are implicated in immune modulations, the significance of LM and LAM as structural components of the mycobacterial cell wall remains unknown. We have previously reported that a branch-forming mannosyltransferase plays a critical role in controlling the sizes of LM and LAM and that deletion or overexpression of this enzyme results in gross changes in LM/LAM structures. Here, we show that such changes in LM/LAM structures have a significant impact on the cell wall integrity of mycobacteria. InMycobacterium smegmatis, structural defects in LM and LAM resulted in loss of acid-fast staining, increased sensitivity to β-lactam antibiotics, and faster killing by THP-1 macrophages. Furthermore, equivalentMycobacterium tuberculosismutants became more sensitive to β-lactams, and one mutant showed attenuated virulence in mice. Our results revealed previously unknown structural roles for LM and LAM and further demonstrated that they are important for the pathogenesis of tuberculosis.IMPORTANCETuberculosis (TB) is a global burden, affecting millions of people worldwide.Mycobacterium tuberculosisis a causative agent of TB, and understanding the biology ofM. tuberculosisis essential for tackling this devastating disease. The cell wall ofM. tuberculosisis highly impermeable and plays a protective role in establishing infection. Among the cell wall components, LM and LAM are major glycolipids found in allMycobacteriumspecies, show various immunomodulatory activities, and have been thought to play roles in TB pathogenesis. However, the roles of LM and LAM as integral parts of the cell wall structure have not been elucidated. Here we show that LM and LAM play critical roles in the integrity of mycobacterial cell wall and the pathogenesis of TB. These findings will now allow us to seek the possibility that the LM/LAM biosynthetic pathway is a chemotherapeutic target.

scholarly journals PHASE-SPECIFIC GENES FOR MACROCONIDIATION IN NEUROSPORA CRASSA

Genetics ◽  
1974 ◽  
Vol 78 (2) ◽  
pp. 679-690 ◽  
Author(s):  
Claude P Selitrennikoff ◽  
Robert E Nelson ◽  
Richard W Siegel
Keyword(s):  
Cell Wall ◽  
Life Cycle ◽  
Neurospora Crassa ◽  
Sexual Life ◽  
Wild Type ◽  
A Cell ◽  
Autolytic Activity ◽  
Sexual Life Cycle ◽  
Mutant Genes ◽  
Active Formation

ABSTRACT Two new mutant genes in Neurospora crassa prevent the formation of free macroconidia from proconidial chains. These genes, called conidial separation-1 and conidial separation-2, are phase-specific, playing no role in either the sexual life cycle or other aspects of the asexual life cycle. A cell-wall-associated autolytic activity was found to increase in wild-type cultures at the time of active formation of free conidia from proconidial chains; no such increase was detected in mutant cultures. It appears that the products of these genes are both essential for and unique to macroconidiation.

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 Role of Hog1 and Yaf9 in the transcriptional response ofSaccharomyces cerevisiaeto cesium chloride

2008 ◽  
Vol 33 (1) ◽  
pp. 110-120 ◽  
Author(s):  
Valerio Del Vescovo ◽  
Viviana Casagrande ◽  
Michele M. Bianchi ◽  
Eugenia Piccinni ◽  
Laura Frontali ◽  
...  
Keyword(s):  
Cell Wall ◽  
Transcriptional Response ◽  
Cesium Chloride ◽  
Wall Structure ◽  
Double Deletion ◽  
Transcriptional Modulation ◽  
A Cell ◽  
Restructuring Process ◽  
Hog1 Phosphorylation

We analyzed the global transcriptional response of Saccharomyces cerevisiae cells exposed to different concentrations of CsCl in the growth medium and at different times after addition. Early responsive genes were mainly involved in cell wall structure and biosynthesis. About half of the induced genes were previously shown to respond to other alkali metal cations in a Hog1-dependent fashion. Western blot analysis confirmed that cesium concentrations as low as 100 mM activate Hog1 phosphorylation. Another important fraction of the cesium-modulated genes requires Yaf9p for full responsiveness as shown by the transcriptome of a yaf9-deleted strain in the presence of cesium. We showed that a cell wall-restructuring process promptly occurs in response to cesium addition, which is dependent on the presence of both Hog1 and Yaf9 proteins. Moreover, the sensitivity to low concentration of cesium of the yaf9-deleted strain is not observed in a strain carrying the hog1/ yaf9 double deletion. We conclude that the observed early transcriptional modulation of cell wall genes has a crucial role in S. cerevisiae adaptation to cesium.

scholarly journals Characterization of Conserved and Novel Septal Factors inMycobacterium smegmatis

2018 ◽  
Vol 200 (6) ◽  
Author(s):  
Katherine J. Wu ◽  
Jenna Zhang ◽  
Catherine Baranowski ◽  
Vivian Leung ◽  
E. Hesper Rego ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Model Organisms ◽  
Wall Structure ◽  
Cross Wall ◽  
Content Type ◽  
A Cell ◽  
Mediate Cell ◽  
Mycobacterial Cell Wall ◽  
Regulatory Functions

ABSTRACTSeptation in bacteria requires coordinated regulation of cell wall biosynthesis and hydrolysis enzymes so that new septal cross-wall can be appropriately constructed without compromising the integrity of the existing cell wall. Bacteria with different modes of growth and different types of cell wall require different regulators to mediate cell growth and division processes. Mycobacteria have both a cell wall structure and a mode of growth that are distinct from well-studied model organisms and use several different regulatory mechanisms. Here, usingMycobacterium smegmatis, we identify and characterize homologs of the conserved cell division regulators FtsL and FtsB, and show that they appear to function similarly to their homologs inEscherichia coli. We identify a number of previously undescribed septally localized factors which could be involved in cell wall regulation. One of these, SepIVA, has a DivIVA domain, is required for mycobacterial septation, and is localized to the septum and the intracellular membrane domain. We propose that SepIVA is a regulator of cell wall precursor enzymes that contribute to construction of the septal cross-wall, similar to the putative elongation function of the other mycobacterial DivIVA homolog, Wag31.IMPORTANCEThe enzymes that build bacterial cell walls are essential for cell survival but can cause cell lysis if misregulated; thus, their regulators are also essential. The number and nature of these regulators is likely to vary in bacteria that grow in different ways. The mycobacteria are a genus that have a cell wall whose composition and construction vary greatly from those of well-studied model organisms. In this work, we identify and characterize some of the proteins that regulate the mycobacterial cell wall. We find that some of these regulators appear to be functionally conserved with their structural homologs in evolutionarily distant species such asEscherichia coli, but other proteins have critical regulatory functions that may be unique to the actinomycetes.

scholarly journals Arabidopsis Trichome Contains Two Plasma Membrane Domains with Different Lipid Compositions Which Attract Distinct EXO70 Subunits

2019 ◽  
Vol 20 (15) ◽  
pp. 3803 ◽  
Author(s):  
Zdeňka Kubátová ◽  
Přemysl Pejchar ◽  
Martin Potocký ◽  
Juraj Sekereš ◽  
Viktor Žárský ◽  
...  
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Apical Cell ◽  
Lipid Binding ◽  
Wall Structure ◽  
Dependent Manner ◽  
Apical Domain ◽  
Transmission Electron ◽  
Target Membrane ◽  
A Cell

Plasma membrane (PM) lipid composition and domain organization are modulated by polarized exocytosis. Conversely, targeting of secretory vesicles at specific domains in the PM is carried out by exocyst complexes, which contain EXO70 subunits that play a significant role in the final recognition of the target membrane. As we have shown previously, a mature Arabidopsis trichome contains a basal domain with a thin cell wall and an apical domain with a thick secondary cell wall, which is developed in an EXO70H4-dependent manner. These domains are separated by a cell wall structure named the Ortmannian ring. Using phospholipid markers, we demonstrate that there are two distinct PM domains corresponding to these cell wall domains. The apical domain is enriched in phosphatidic acid (PA) and phosphatidylserine, with an undetectable amount of phosphatidylinositol 4,5-bisphosphate (PIP2), whereas the basal domain is PIP2-rich. While the apical domain recruits EXO70H4, the basal domain recruits EXO70A1, which corresponds to the lipid-binding capacities of these two paralogs. Loss of EXO70H4 results in a loss of the Ortmannian ring border and decreased apical PA accumulation, which causes the PA and PIP2 domains to merge together. Using transmission electron microscopy, we describe these accumulations as a unique anatomical feature of the apical cell wall—radially distributed rod-shaped membranous pockets, where both EXO70H4 and lipid markers are immobilized.

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