Diverse organizations of actin and nuclei underpin the evolution of indeterminate growth in Chytridiomycota and Dikarya

Botany ◽  
2021 ◽  
Author(s):  
Jaclyn Marie Dee ◽  
Mary Berbee
Keyword(s):  
Cell Wall ◽  
Light Microscopy ◽  
Somatic Growth ◽  
Nuclear Migration ◽  
Nuclear Staining ◽  
Nuclear Positioning ◽  
Indeterminate Growth ◽  
Rhodamine Phalloidin ◽  
Actin Organization ◽  
Cell Wall Remodeling

Indeterminate growth, as in the hyphae of the “Humongous Fungus” of Michigan requires sustained nuclear migration and cell wall remodeling. We compare actin organization and patterns of nuclear positioning among four distantly related, indeterminate species of phylum Chytridiomycota: Cladochytrium replicatum, Physocladia obscura, Nowakowskiella sp., and Polychytrium aggregatum. We combined light microscopy, nuclear staining with DAPI, and actin staining with rhodamine phalloidin to analyze actin distribution and nuclear migration during somatic growth in the four Chytridiomycota species. Actin formed plaques, filaments, cables and perinuclear shells in patterns that varied across the four species. All four species initiated indeterminate growth by extending branching, anucleate rhizomycelium, <1 µm in diameter. Nuclei, some elongated as if migrating, first appear in intercalary segments that widened to diameters >1 µm. After mitosis, an intercalary swelling in C. replicatum became septate and a single, distal nucleus migrated tipwards to a new swelling. In Physocladia obscura, swellings were aseptate and multinucleate, and several nuclei migrated tipwards into a new swelling. Nuclei migrated tipwards from irregularly cylindrical filaments in Nowakowskiella sp., and in Polychytrium aggregatum, from regular, hypha-like filaments. Thus, distantly related lineages of zoosporic fungi deploy ancestral morphogenetic machinery in differing patterns that resulted in convergent, indeterminate growth.

Actin has multiple roles in the formation and architecture of zoospores of the oomycetes, Saprolegnia ferax and Achlya bisexualis

1992 ◽  
Vol 102 (3) ◽  
pp. 611-627 ◽  
Author(s):  
I. BRENT HEATH ◽  
RUTH L. HAROLD
Keyword(s):  
Cell Wall ◽  
Germ Tube ◽  
Multiple Roles ◽  
Rhodamine Phalloidin ◽  
Saprolegnia Ferax ◽  
Functional Changes ◽  
Specific Effects ◽  
Changing Patterns ◽  
Microtubular Root ◽  
Achlya Bisexualis

Very similar changing patterns of actin are described with rhodamine-phalloidin labelling during the zoosporic life cycle of the oomycetes, Saprolegnia ferax and Achlya bisexualis. By comparing the changes with previously described ultrastructural and functional changes, we show that actin functions in numerous previously unrecognized processes. Most spectacularly, the directed vesicle expansions of the cytokinetic system involve newly formed actin which outlines the developing zoospores. Disruption of this actin with cytochalasins leads to abnormal cleavage as witnessed by the formation of enlarged and irregular cysts. Prior to cytokinesis, two new types of organelle are synthesized and one, known as K bodies, clusters around the nuclei. These organdies are actin-rich during development and clustering, consistent with actin functioning in their positioning. In the zoospores, actin is concentrated around the water expulsion vacuoles, indicating that they are contractile, and permeates the cytoplasm, probably with a skeletal role. This concept is supported by the first demonstration of actin specifically associated with a microtubular root in the secondary zoospore. Upon encystment there is a dramatic increase in stained actin in the form of peripheral plaques associated with the newly synthesized cell wall. When the cysts germinate, a fibrillar actin cap, comparable to that previously described in hyphal tips, forms in the germ tube apex, but only after cell wall softening to permit germ tube protrusion. This sequence is consistent with the actin cap modulating turgor-driven expansion of the tip as previously discussed for hyphae. In addition to disrupting cleavage-associated actin, cytochalasins show developmental stage, dose and drug (CE≥CD≥CB) specific effects on zoosporulation-related actin, which indicates that, contrary to previous suggestions, rhodamine-phalloidin staining is a useful indicator of actin behaviour in response to cytochalasins. These responses include differential effects on adjoining actin arrays, some of which are transient in the continued presence of the drugs, indicating a mechanism of drug adaptation.

scholarly journals Effects of the pollution by petroleum on the tracheids along the stem of Podocarpus lambertii Klotzsch ex Endl., Podocarpaceae

2009 ◽  
Vol 69 (2) ◽  
pp. 263-269 ◽  
Author(s):  
LT. Maranho ◽  
M. Dziedzic ◽  
GIB. Muñiz ◽  
YS. Kuniyoshi ◽  
F. Galvão
Keyword(s):  
Cell Wall ◽  
Light Microscopy ◽  
Ground Level ◽  
Plant Anatomy ◽  
Southern Brazil ◽  
Growth Layer ◽  
Wall Width ◽  
Control Set ◽  
Student’S T ◽  
Student’S T Test

Podocarpus lambertii Klotzsch ex Endl. (Podocarpaceae) is native and a member of the Pinophyta (Gymnosperm) of southern Brazil, locally known as "pinheiro-bravo". The present work aims to investigate the effects of petroleum on the tracheids dimensions. Wood samples from twenty individuals were studied along the stem, ten being exposed to pollution and ten used as a control set. The wood samples were collected from incisions at three levels: at the ground level, and one and two metres above the ground level. From these samples, sub-samples were selected at the border of the growth layers in the vascular cambium-medulla direction. The methodology followed that traditionally recommended for plant anatomy studies, with analyses done by light microscopy (OLYMPUS - BX41) assisted by the software Image Pro-plus for measurements. Comparison of the individuals exposed to petroleum with the control set, showed that the length, diameter and cell wall width of the tracheids of the former were smaller, a trend which was statistically significant according to the Student's t-test. These traits were observed mainly on the tracheids of the last growth layer, corresponding to the year in which the individuals were exposed to petroleum.

scholarly journals Hitting the Wall—Sensing and Signaling Pathways Involved in Plant Cell Wall Remodeling in Response to Abiotic Stress

Plants ◽  
2018 ◽  
Vol 7 (4) ◽  
pp. 89 ◽  
Author(s):  
Lazar Novaković ◽  
Tingting Guo ◽  
Antony Bacic ◽  
Arun Sampathkumar ◽  
Kim Johnson
Keyword(s):  
Cell Wall ◽  
Abiotic Stress ◽  
Plant Hormones ◽  
Plant Cell Wall ◽  
Key Factors ◽  
Cell Wall Remodeling ◽  
Dynamic Cell ◽  
Adverse Environmental Conditions ◽  
Cell Wall Deposition ◽  
Cell Wall Properties

Plant cells are surrounded by highly dynamic cell walls that play important roles regulating aspects of plant development. Recent advances in visualization and measurement of cell wall properties have enabled accumulation of new data about wall architecture and biomechanics. This has resulted in greater understanding of the dynamics of cell wall deposition and remodeling. The cell wall is the first line of defense against different adverse abiotic and biotic environmental influences. Different abiotic stress conditions such as salinity, drought, and frost trigger production of Reactive Oxygen Species (ROS) which act as important signaling molecules in stress activated cellular responses. Detection of ROS by still-elusive receptors triggers numerous signaling events that result in production of different protective compounds or even cell death, but most notably in stress-induced cell wall remodeling. This is mediated by different plant hormones, of which the most studied are jasmonic acid and brassinosteroids. In this review we highlight key factors involved in sensing, signal transduction, and response(s) to abiotic stress and how these mechanisms are related to cell wall-associated stress acclimatization. ROS, plant hormones, cell wall remodeling enzymes and different wall mechanosensors act coordinately during abiotic stress, resulting in abiotic stress wall acclimatization, enabling plants to survive adverse environmental conditions.

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