Disruption of the microtubule network alters cellulose deposition and causes major changes in pectin distribution in the cell wall of the green alga,Penium margaritaceum

Cells of the green alga, Apjohnia laeterivens Harvey, have been ruptured in a Waring blendor in order to remove the majority of the protoplast from the cell-wall substances. The cell walls have been shown to contain, apart from extraneous protoplasmic constituents and some encrusting bryozoa, framework microfibrils of cellulose 1 which seem to be associated with pectin-like materials, arabinogalactan matrix substances and, perhaps, a polysaccharide-protein complex; these components appear to represent about 90% of the organic substances in the original organic-solvent extracted cell walls. Less than 25 % of the initial cellulose 1 was converted to cellulose 11 during treatments of several hours' duration at room temperature with aqueous solutions of 24% KOH and 17.5 % NaOH. The low degree of conversion is attributed to the presence of highly ordered and/or large "crystalline" aggregates of �-1,4'-glucan molecules in the cellulosic micelles of the framework microfibrils of the cell walls.

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Xyloglucan Is Not Essential for the Formation and Integrity of the Cellulose Network in the Primary Cell Wall Regenerated from Arabidopsis Protoplasts

Plants ◽

10.3390/plants9050629 ◽

2020 ◽

Vol 9 (5) ◽

pp. 629 ◽

Cited By ~ 3

Author(s):

Hiroaki Kuki ◽

Ryusuke Yokoyama ◽

Takeshi Kuroha ◽

Kazuhiko Nishitani

Keyword(s):

Cell Wall ◽

Cellulose Microfibril ◽

Mechanical Stability ◽

Molecular Model ◽

Primary Cell ◽

Cellulose Microfibrils ◽

Primary Cell Wall ◽

Imaging Analysis ◽

Cellulose Deposition ◽

Initial Assembly

The notion that xyloglucans (XG) play a pivotal role in tethering cellulose microfibrils in the primary cell wall of plants can be traced back to the first molecular model of the cell wall proposed in 1973, which was reinforced in the 1990s by the identification of Xyloglucan Endotransglucosylase/Hydrolase (XTH) enzymes that cleave and reconnect xyloglucan crosslinks in the cell wall. However, this tethered network model has been seriously challenged since 2008 by the identification of the Arabidopsis thaliana xyloglucan-deficient mutant (xxt1 xxt2), which exhibits functional cell walls. Thus, the molecular mechanism underlying the physical integration of cellulose microfibrils into the cell wall remains controversial. To resolve this dilemma, we investigated the cell wall regeneration process using mesophyll protoplasts derived from xxt1 xxt2 mutant leaves. Imaging analysis revealed only a slight difference in the structure of cellulose microfibril network between xxt1 xxt2 and wild-type (WT) protoplasts. Additionally, exogenous xyloglucan application did not alter the cellulose deposition patterns or mechanical stability of xxt1 xxt2 mutant protoplasts. These results indicate that xyloglucan is not essential for the initial assembly of the cellulose network, and the cellulose network formed in the absence of xyloglucan provides sufficient tensile strength to the primary cell wall regenerated from protoplasts.

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The Ultrastructure of Fertilization and Zygote Formation in the Green Alga Ulva Mutabilis Føyn

Journal of Cell Science ◽

10.1242/jcs.9.3.621 ◽

1971 ◽

Vol 9 (3) ◽

pp. 621-635

Author(s):

T. BRÅTEN

Keyword(s):

Cell Wall ◽

Green Alga ◽

Initial Contact ◽

Zygote Formation ◽

Cell Wall Formation ◽

Wall Formation ◽

Electron Microscopes ◽

Scanning Electron Microscopes ◽

Scanning Electron ◽

Cell Cell

Fertilization and zygote formation in the multicellular green alga Ulva mutabilis Føyn were studied with the aid of transmission and scanning electron microscopes. The growth mutant ‘slender’ was used in this investigation. The initial contact between mating gametes is made by the flagella, whereupon cytoplasmic contact is established within a few seconds. Fusion of the cytoplasm of the 2 cells is completed in 5 min and the nuclei can be seen to fuse 30 min after the onset of copulation. The settling of the young zygotes initiates a process during which the 4 flagella are absorbed into the cell. Cell wall formation also starts when the zygotes settle. Observations indicate disintegration of one of the 2 chloroplasts in the young zygote.

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