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Hartig, K; Beck, E: Crosstalk between auxin, cytokinins, and sugars in the plant cell cycle, Plant Biology, 8, 1-8 (2006)
Key words: cell cycle, auxin, cytokinin, sugar, tobacco BY-2 cells
Abstract:
Plant meristems are utilization sinks, in which cell division activity governs sink strength. However, the molecular mechanisms by which cell division activity and sink strength are adjusted to a plant’s developmental program in its environmental setting are not well understood. Mitogenic hormonal as well as metabolic signals drive and modulate the cell cycle, but a coherent idea of how this is accomplished, is still missing. Auxin and cytokinins are known as endogenous mitogens whose concentrations and timing, however, can be externally affected. Although the sites and mechanisms of signal interaction in cell cycle control have not yet been unravelled, crosstalk of sugar and phytohormones signals could be localized to several biochemical levels. At the expression level of cell cycle control genes, synergistic but also antagonistic interactions could be demonstrated. Another level of crosstalk is that of signal generation or modulation. Cytokinins affect the activity of extracellular invertases and hexose-uptake carriers and thus impinge on an intracellular sugar signal. With tobacco BY-2 cells, a coordinated control of cell cycle activity at both regulatory levels could be shown. Comparison of the results obtained with the root cell-representing BY-2 cells with data from shoot tissues or green cell cultures of Arabidopsis and Chenopodium suggests tissue-specific regulatory patterns of mitogenic signals and signal crosstalk. Growth of roots and division of BY-2 cells are retarded by an elevated cytokinin supply reflecting an inhibitory effect of cytokinins on the expression of cyclinD2;1 which is under synergistic positive control of auxin and sugar. Likewise cytokinins inhibit the extracellular invertase and thereby attenuate the sugar signal. This contrasts with meristematic shoot cells where cyclinD2;1 expression is synergistically regulated by auxin, cytokinins and sugar, and intracellular invertase activity is induced by cytokinins.

last modified 2006-11-10