Ciereszko I, Kleczkowski LA
Effects of phosphate deficiency and sugars on expression of rab18 in Arabidopsis: hexokinase-dependent and okadaic acid-sensitive transduction of the sugar signal
Biochimica Et Biophysica Acta-Gene Structure and Expression: 2002 1579:43-49
Sucrose synthase (SuSy) is an important enzyme involved in sucrose synthesis/breakdown in all plants. Sus1, a major SuSy gene in Arabidopsis thaliana, was upregulated by sucrose, glucose and D-mannose, but not 3-O-methylglucose, when those compounds were fed to excised leaves. Mannos, was more effective than glucose or sucrose in the induction of Sus1, with strong effects observed at a concentration as low as 20, mM. When fed to the excised leaves, N-acetyl-glucosamine, an inhibitor of hexokinase (HXK) enzymatic activity, decreased sucrose- and glucose-dependent, but not mannose-dependent, upregulation of Sus1. The sucrose/glucose-dependent Sus1 expression was strongly induced in transgenic Arabidopsis HXK-overexpressing (OE) plants, whereas mannose-dependent Sus1 expression markedly decreased in OE, but not in HXK-"antisense", Arabidopsis plants. Feeding with sucrose resulted in a marked increase of glucose content in leaves, suggesting that it is glucose rather than sucrose that serves as a signal in upregulating Sus1 expression in sucrose-fed plants. The data suggest that Sus1 is regulated by a HXK-dependent pathway, with glucose and mannose effects differentially sensed/transmitted via the HXK step. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.
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