The control of source to sink carbon flux during tuber development in potato (original) (raw)

We have used top-down metabolic control analysis to investigate the control of carbon flux through potato (Solanum tuberosum) plants during tuberisation. The metabolism of the potato plant was divided into two blocks of reactions (the source and sink blocks) that communicate through the leaf apoplastic sucrose pool. Flux was measured as the transfer of 14 C from CO 2 to the tuber. Flux and apoplastic sucrose concentration were varied either by changing the light intensity or using transgenic manipulations that specifically affect the source or sink blocks, and elasticity coefficients were measured. We have provided evidence in support of our assumption that apoplastic sucrose is the only communicating metabolite between the source and sink blocks. The elasticity coefficients were used to calculate the flux control coefficients of the source and sink blocks, which were 0.8 and 0.2, respectively. This work suggests that the best strategy for the manipulation of tuber yield in potato will involve increases in photosynthetic capacity, rather than sink metabolism. A 'top-down' approach to the determination of control coefficients in metabolic control theory. Eur. J. Biochem. 188, 321-325. Collins, W.B. (1976) Effect of carbon dioxide enrichment on growth of the potato plant. Hort. Sci. 11, 467-469. Engels, C. and Marschner, H. (1986a) Allocation of photosynthate to individual tubers of Solanum tuberosum L. I. Relationship between tuber growth rate and enzyme activities of the starch metabolism. J. Exp. Bot. 37, 1795-1803. Engels, C. and Marschner, H. (1986b) Allocation of photosynthate to individual tubers of Solanum tuberosum L. III. Relationship between growth rate of individual tubers, tuber weight and stolon growth prior to tuber initiation. J. Exp. Bot. 37, 1813-1822. Entwistle, G. and ap Rees, T. (1990) Lack of fructose-1,6bisphosphatase in a range of higher plants that store starch.

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