Cellulose in tunicates

Figure 9 Raman spectra of tunicate (Halocynthia roretzi) and Valonia macrophysa celluloses in the Raman active regions.

There are several polymorphs of crystalline cellulose-I, II, III, and IV. Each has been extensively studied [4]. Crystalline cellulose that is naturally produced by a variety of organisms, it is sometimes referred to as "natural cellulose. Cellulose-I has two polymorphs, a triclinic structure [ ) and a monoclinic structure [I ], which coexist in various proportions depending on the cellulose source. The Iq structure is the dominate polymorph for most algae and bacteria, whereas is the dominant polymorph for higher plant cell wall cellulose and in tunicates [5-7]. Allomorph ratios are species specific, and this gives rise to natural structural variations in cellulose crystals. However, the mechanisms contributing to crystal formation remain unknown [8]. 

Early descriptions of the occurrence of cellulose in the tunicates were provided by Berrill (1950) and Endean (1955a, b, 1961). Berrill (1950) described that the tunic contains approximately 60% cellulose, 27% nitrogen-containing components and, in the fresh condition, approximately 90% water. The development of the tunic... 

Studies on the biogenesis of cellulose microfibrils in the tunicates have focused mainly on the tunic of ascidians. Results from studies with various species of ascidians have suggested that the epidermal cell is the most probable site for synthesis of tunic cellulose in the majority of ascidians (Millar 1951 Deck et al. 1966 Dilly 1969 Cloney and Grimm 1970 Smith 1970 Terakado 1970 Wardrop 1970 Stievenart 1971 Katow and Watanabe 1978 Torrence and Cloney 1981 Cloney and Cavey 1982 Robinson et al. 1983). However, these early studies did not show the details of the mechanism and the exact site of synthesis of cellulose in the epidermal cell of ascidians. 

The structural features of cellulose microfibrils in these pelagic tunicates are quite similar to that of ascidians. This evidence indicates that the cellulose-synthesizing ability is an inherited character common to ascidians and thaliaceans. It is also reported that the basic structures of the tunic and the epidermis of ascidians and thaliaceans are almost the same (Hirose et al. 1999). The timic cellulose in the thaliaceans may be synthesized by TCs on the plasma membrane of epidermal cells similar to the ascidians. 

OCCURRENCE OF HIGHLY CRYSTALLINE CELLULOSE IN THE MOST PREMHIVE TUNICATE, THE APPENDICULARIANS... 

Electron microscopic analyses revealed the structure, assembly, bundling and functions of cellulose in the tunicates. For the first time, cellulose-synthesizing enzyme complexes (TCs) of new type and shape were found on epidermal cells, just under the tunic, in several species of ascidians. Current evidence supports... 

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