68. Brown, R. M., Jr. and J. H. M. Willison.
1977. Golgi apparatus and plasma membrane involvement in secretion
and cell surface deposition. Proc. First Int. Cong. Cell Biol.
(Boston). IN: International Cell Biology 1976. (B. R. Brinkley
and K.R. Porter, eds.). Rockefeller University Press. pp. 267-283.
68. Abstract
The cell wall is an extracellular covering
of the plant cell. It functions in the protection of the protoplasm
from environmental stress, and it serves as a structural skeleton.
Furthermore, patterns of growth and differentiation are governed
largely by the biosynthetic processes leading to the assembly
of the cell wall. As a specialized type of extracellular matrix,
the cell wall can be regarded as a preserved record (like geological
strata) of a series of successive stages in a time-sequence of
metabolic, transport, and depositional events. The fundamental
components of the cell wall include a microfibrillar reinforcing
network which lies in a gel-like matrix of interlinked molecules.
The matrix consists of protein, hemicelluloses, and pectins;
the reinforcing rods are comprised of -1,4-linked glucan chains
crystallized into microfibrils of cellulose. Cell walls are of
more than theoretical importance to cell biologists. Cellulose
is the most abundant product on earth and is of great commercial
value. It is a natural polymer, having features equivalent to
several man-made polymers, yet its in vitro synthesis
remains to be accomplished. The purpose of this presentation
is to report new observations of cell wall biogenesis, using
a variety of organisms and experimental approaches. To this end,
the authors are grateful to the following individuals who have
contributed major facts to our group effort: Richard Santos, Dwight
Romanovicz, David Montezinos, and Susette Mueller. The theme
of our presentation concerns the synthesis of cellulose and the
role of the endoplasmic reticulum, Golgi apparatus and plasma
membrane in its biogenesis. The non-cellulosic wall components
will not be discussed, and the reader is referred to a recent
review (Chrispeels, 1976) for a more complete coverage of secretion
and cell walls. Clearly, an understanding of cellulose synthesis
is the key to understanding cell wail biogenesis (Preston, 1~74).
Progress in this particular area of plant cell biology may have
been slow for two reasons: (1) technological limitations; and
(2) inappropriate choice of suitable experimental organisms (which
has led to the failure to test hypotheses on cellulose formation
critically) The descriptions of cellulose formation that fol-low
will be largely cytological; however, in the cases of Pleurochrysis
(Brown and Romanovicz, 1976; Romanovicz and Brown, 1976). Acetobacter
(Cooper and Manley, 1975), and corn (Wright and Northcote, 1'1)76),
a large compilation of supporting biochemical evidence is available.