Cellulose microfibrils deposition

Hasezawa, S. and Nozaki, H. 1999. Role of cortical microtubules in the orientation of cellulose microfibril deposition in higher-plant cells. Protoplasma 209, 98-104... 

Sugimoto K., Himmelspach R., Williamson R.E., and Wasteneys G.O. 2003. Mutation or drug-dependent microtubule disruption causes radial swelling without altering parallel cellulose microfibril deposition in Arabidopsis root cells. The Plant Cell 15 1414-1429. 

Mueller S.C. and Brown, Jr. R.M. 1982. The control of cellulose microfibril deposition in the cell wall of higher plants. Planta 154 501-515. 

Figure 1. Freeze-dried gel of A. xylinum cellulose ribbons deposited during normal growth. The arrows point to triple-stranded left-hand helical microfibrils averaging 36.8 3A in diameter (1). The sample was replicated with 17.3A Pt-C and backed with 90.2A of carbon. 

Secondary-cellulose deposition occurs after cessation of expansion of the primary wall. Layers of the secondary wall, in contrast to the primary wall, display a very orderly, parallel arrangement of the microfibrils. In such plants as flax and hemp,1,2 bamboo,13 sisal,14-16 cotton hairs,2 and pine tracheids,13 three main layers can be detected in the secondary wall, each made up of cellulose microfibrils arranged in a helical fashion around the cell, In each of these secondary walls, the middle layer of cellulose is considerably thicker than the cellulose layers on each side of it, with a helical direction opposed to those of the latter. It is probable that each of these three layers is, in fact, complex, and made from a number of lamellae, each with its own helix of cellulose microfibrils.1 2... 

B. A Model of Cellulose-Fibril Deposition During Secondary-wall Formation in Microsterias.7 [Each rosette is believed to form one 5-nm microfibril. A row of rosettes forms a set of 5-nm microfibrils which aggregate laterally to form the larger fibrils of the secondary wall. Above side view. The stippled area in the center of a rosette represents the presumptive site of microfibril formation, although details of its structure, composition, and enzymic activity remain unclear. Below surface view, with expanded, cross-sectional view of cellulose fibrils.]... 

Polymerization of the D-glucan chains occurs by way of a multi-subunit, enzyme complex embedded in the plasma membrane an almost simultaneous association, by means of hydrogen bonds, of the newly formed chains results in formation of partially crystalline microfibrils. This mechanism of polymerization and crystallization results in the creation of microfibrils whose chains are oriented parallel (cellulose I). In A. xylinum, the complex is apparently immobile, but, in cells in which cellulose is deposited as a cell-wall constituent, it seems probable that the force generated by polymerization of the relatively rigid microfibrils propels the complex through the fluid-mosaic membrane. The direction of motion may be guided through the influence of microtubules. 

As will be discussed later (see p. 332), these data provide strong support for the argument that the microfibrils are produced by on-the-site synthesis and orientation (apposition) of the cellulosic microfibrils under the guiding influence of the living cell, rather than by a mechanism that proposes synthesis of the micro fibrils within the cell and subsequent translocation and crystallization (deposition) of microfibrils on the cell wall by exocellular factors. Further factors relevant to these opposing theories emerge from study of the fine structure of the cellulosic microfibrils, as discussed in the following Section. 

The chemical nature of the carbohydrate matrix and the orientation of the cellulose microfibrils influence lignin deposition. In the middle lamella and the primary wall, lignin forms spherical structures, whereas in the secondary wall, lignin forms lamellae that follow the orientation of the microfibrils [20, 24, 94]. 

Brett CT. (2000). Cellulose microfibrils in plants biosynthesis, deposition, and integration into the cell wall. Int Rev Cytol, 199, 161-199. 

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