The perturbation of the endomembrane network of the chlamydomonad alga Gloeomonas by the herbicide isopropyl N-phenyl carbamate (IPC)

Abstract. The highly complex and symmetric endomembrane network of the chlamydomonad alga, Gloeomonas kupferri , can be disrupted by the herbicide, isopropyl N-phenyl carbamate (IPC). Upon incubation with IPC for between 30 min and 1 h, curling of the dictyosomes, proliferation of small vesicles from the trans face and swelling of the peripheral vacuolar complex takes place. Longer treatments result in degeneration of dictyosome cisternae into vesicular masses and the formation of supervacuolar complexes. Enzyme cytochemistry revealed that endomembrane 'marker' enzymes are altered/inhibited by IPC. A second but striking I PC-induced effect is the production of branched, fibrillar inclusions in the cell nucleus. A discussion of I PC-induced affects on ion regulation and microtubule/MTOC distribution in the cell is presented.     

Colchicine-Induced Effects in the Scaly Green Alga, Mesostigma viride: Loss of Microtubules and Paracrystal Formation

The effects of colchicine treatment upon the scale-covered,disc-shaped prasinophyte, Mesostigma viride, are profound. 2–4mg ml^–1 of the alkaloid induces the loss of pit and othercytoskeletal microtubules within 6 h of treatment. Subsequently,the organism loses its distinctive shape and becomes ellipsoidal.During treatment, prominent, intracellular crystalline bandsconsisting of 25 nm hexagonal subunits form in close proximityto the former pit region. The Golgi apparatus remains intactduring colchicine application but scale ontogenesis is distinctlyaltered. All effects are reversible upon removal of colchicine.A discussion of the cytoskeletal role of parallel series ofmicrotubules in unicellular algae is presented. Key words: Mesostigma, Colchicine, Cytoskeletal     

Photosynthetic Eukaryotes of Freshwater Wetland Biofilms: Adaptations and Structural Characteristics of the Extracellular Matrix in the Green Alga, Cosmarium reniforme (Zygnematophyceae, Streptophyta)

ABSTRACT. Cosmarium reniforme (Zygnematophyceae, Streptophyta) is a green alga that is commonly found in biofilms of wetlands of the Adirondack region, NY (USA). Two distinctive characteristics that are critical to this alga's survival in a benthic biofilm are its elaborate cell morphology and extracellular matrix (ECM). In this study, ultrastructural, immunocytochemical, and experimental methodologies were employed in order to elucidate the cellular characteristics that are critical for survival in a biofilm. The ECM consists of a thick, outwardly lobed cell wall (CW), which contains a patterned network of structurally complex pores. Each pore consists of a narrow channel, terminating internally at a bulb that invaginates localized regions of the plasma membrane. The outer region of the pore contains arabinogalactan protein-like and extensin epitopes that are likely involved in adhesion mechanisms of the cell. External to the CW is the extracellular polymeric substance that is employed in ensheathment of the cell to the substrate and in gliding motility. The architectural design/biochemical make-up of the CW and a secretory system that encompasses the coordinated activities of the endomembrane and cytomotile/cytoskeletal systems provide the organism with effective mechanisms to support life within the biofilm complex.     

The Disruption of Dictyosome Structure, Polarity and Secretory Activity in the Scale-producing Green Alga, Pyramimonas inconstans

Domozych, D. S. and Korbusieski, T. J. 1985. The disruptionof dictyosome structure, polarity and secretory activity inthe scale-producing green alga Pyramimonas inconstans.—J.exp.Bot.36: 1304–1312. Dictyosome morphology and scale morphogenesis in the green alga,Pyramimonas inconstans, are well-defined ultrastructurally.By applying the sodium-specific ionophore, monensin, to actively-growingcell cultures, both dictyosome micro-architecture and the scale-basedsecretory pathway can be significantly altered. Applicationof 0.1 mol m³ and 0.01 mol m ^–3monensin for short periods(1 -3 h) results in cisternal curling and the disorientationof dictyosome polarity. Prolonged exposure to the ionophore(4-24 h) results in the complete disruption of dictyosome morphologyand scale morphogenesis with the emergence of irregular vesiclesfrom the maturing face. Removal of monensin by repeated washingreturns dictyosome structure and secretory activity to normal.These results indicate that Golgi apparatus integrity and secretoryactivity in Pyramimonas may be controlled by a localized, cytoplasmicproton gradient Key words: Monensin, Pyramimonas, dictyosome     

An Experimental Analysis of the Dictyosome in the Green Alga, Tetraselmis convolutae

Domozych, D. S. 1987. An experimental analysis of the dictyosomein the green alga, Tetraselmis convolutae.—J. exp. Bot.38: 1399–1411. Tetraselmis convolutae possesses two well-defined, polar-orienteddictyosomes. These endo-membrane components have various functionsthat change during the cell cycle phases. The dictyosomes arealso very sensitive to various subcellular poisons. Disruptionof the cellular ionic balance with monovalent ionophores yieldsmaturing face curling, swelling and the production of unusualmultivesicular elements. Divalent ionophore application alsoimpairs maturing face vesiculation and vesicle transport inthe anterior cytoplasm. Caffeine restricts maturing face vesicleproduction, subsequently leading to gross enlargement of cisternallength. Application of the microtubule-inhibitor, colchicine,and the MTOC-affecting agent, IPC, leads to polar axis disruptionof the dictyosome and the formation of multiple, cisternal stacks.A discussion of dictyosome-microtubule-MTOC associations ispresented. Key words: Tetraselmis, dictyosome, disruption