Cell Wall Assembly in Fucus Zygotes

Abstract

Fertilization triggers the assembly of a ceDl wai around the egg cell of three brown algae, Fucus vesiculosus, F. distichus, and F. inflatus ratio of fucose to xylose and high levels of sulfate, and contain a second fucan (F2) which is electrophoreticaDly distinct from F1. F2 appears to be deposited in only a localized region of the wall, that which elongates to form the rhizoid ceDl. Throughout wall assembly, the polyuronide block co-polymer alginic acid did not significantly vary its mannuronic (M) to guluronic (G) acid ratio (0.33-0.55) or its block distribution (MG, 54%; GG, 30%; MM, 16%). From 6 to 24 hours of embryo development, the proportion of the major polysaccharide components found in purified walls is stable. Alginic acid is the major polymer and comprises about 60% of the total wall, while cellulose and the fucans each make-up about 20% of the remainder. During the extracellular assembly of this wall, the intrcellular levels of the storage glucan laminaran decreases. A membrane-bound 3-1,3-exoglucanase is found in young zygotes which degrades laminaran to glucose. It is postulated that hydrolysis of laminaran by this glucanase accounts, at least in part, for glucose availability for wall biosynthesis and the increase in respiration triggered by fertilization. The properties and function of alginic acid, the fucans, and cellulose are discussed in relation to changes in wall structure and function during development.The developmental processes of growth, differentiation, and morphogenesis in plant cells are all intimately associated with I

Membrane fusion process and assembly of cell wall during cytokinesis in the brown alga, Silvetia babingtonii (Fucales, Phaeophyceae)

“…Sites of unstable membrane configuration are rich in fucoidan Localization of polysaccharides within the cell wall of fucoid zygotes, revealed that the first detectable cell wall component after fertilization is alginate, and that the proportion of cellulose in the cell wall becomes equal to that of alginate within 1 h after fertilization (Quatrano and Crayton 1973;Novotny and Forman 1974;Quatrano and Stevens 1976;Callow et al 1978;Brawley and Quatrano 1979). The fucoidan contents increase from initiation of rhizoid formation and the rhizoid cell has fucoidan-rich cell wall (Novotny and Forman 1974;Quatrano and Stevens 1976;Callow et al 1978).…”

“…The fucoidan contents increase from initiation of rhizoid formation and the rhizoid cell has fucoidan-rich cell wall (Novotny and Forman 1974;Quatrano and Stevens 1976;Callow et al 1978). Localization of fucoidan has been examined by analysis using toluidine blue O staining or autoradiographic techniques, which indicated that sulfated polysaccharides may be synthesized in the Golgi bodies and transported to the plasma membrane via vesicles (Evans et al 1973;Callow et al 1978;Brawley and Quatrano 1979).…”

“…The cell wall of brown algae consists of cellulose, acidic polysaccharides (alginate and sulfated fucans), phenolic compounds and a small amount of protein (Quatrano and Stevens 1976;Kloareg and Quatrano 1988;Schoenwaelder and Clayton 1998a, 1998b. The alginates, which are a major component of cell wall in brown algae, are linear heteropolysaccharides composed of -1,4 linked L-guluronic acid and -1,4 D-mannuronic acid (Haug et al 1966).…”

Sulfation of fucoidin in focus embryos: III. Required for localization in the rhizoid wall

“…At least a portion of the galactose is found as the terminal sugar in the chain(s) (11), and various chemical fractionation schemes have described a range of polymers with differing amounts of these sugar and uronic acid residues (10). However, by electrophoresis in two different buffers, the sulfated polysaccharides from each of the three major chemical fractions displayed essentially the same two subfractions (20). This group of polysaccharides containing fucose sulfate as the predominant monomer unit will be referred to as fucoidin, while the same sugar chains that lack sulfate will be termed fucan.…”

“…F, has a lower electrophoretic mobility, is not so heavily sulfated and contains less fucose and more uronic acid moieties than F2. The early cell wall contains only F, while F2 is incorporated into the wall at the time of rhizoid formation (20).…”