Rationale for Future Transgenic Work

According to the summation theorem of Metabolic Control Analysis (MCA) (Kacser and Burns 1973 Heinrich and Rapoport 1974 Kell and Westerhoff 1986 Cornish-Bowden et al. 1995 Fell 1996 Heinrich and Schuster 1996), changes in the concentrations of individual enzymes within a metabolic pathway tend to have little effect on metabolic fluxes and on the phenotype under most conditions (Thatcher et al. 1998). However, changes in individual enzyme concentrations could affect the size of metabolite pools even when the alterations in flux are minimal. Because of mass aetion effeets, the change in a metabolic pool could lead to a shift of other eoupled metabolites and change the flux at the nonequilibrium reactions in the pathway. 

Overexpression of a cellulose-binding domain (CBD) has been reported to result in increased cellulose produetion in poplar (Levy et al. 2002). It was proposed that the CBD increased the rate of eellulose production by slowing down the rate of crystallization of the gluean ehains into mierofibrils, which is believed to limit the rate of cellulose synthesis in intact cells. This idea is based on the earlier finding that calcofluor white, a fluorescent dye commonly used to deteet cellulose, interfered with the crystallization of the gluean chains into mierofibrils (Haigler et al. 1980). 

Aloni Y, Delmer D.P., and Benziman M. 1982. Achievement of high rates of in vitro synthesis of 1,4-P-D-glucan activation by cooperative interaction of the Acetobacter xylinum enzyme system with GTP, polyethylene glycol and protein factor. Proc Natl Acad Sci USA 79 6448-6452. 

Appenzeller L., Doblin M., Barreiro R., Wang H., Niu X., Kollipara K., Carrigan L., Tomes D., Chapman M., and Dhugga K.S. 2004. Cellulose synthesis in maize isolation and expression analysis of the cellulose synthase CesA) gene family. Cellulose 11 287-299. 

Arioli T., Peng L., Betzner Andreas S., Bum X, Wittke W., Herth W., Camilleri C., Hofte H., Plazinski X, Birch R., Cork A., Glover X, Redmond X, and Williamson R.E. 1998. Molecular analysis of cellulose biosynthesis in Arabidopsis. Science 279 717-720. 

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