title: Functional dissection of sugar signals affecting gene expression in Arabidopsis thaliana.
abstract: BACKGROUND
  Sugars modulate expression of hundreds of genes in plants. Previous studies on sugar signaling, using intact plants or plant tissues, were hampered by tissue heterogeneity, uneven sugar transport and/or inter-conversions of the applied sugars. This, in turn, could obscure the identity of a specific sugar that acts as a signal affecting expression of given gene in a given tissue or cell-type.
  
  
  RESULTS
  To bypass those biases, we have developed a novel biological system, based on stem-cell-like Arabidopsis suspension culture. The cells were grown in a hormone-free medium and were sustained on xylose as the only carbon source. Using functional genomics we have identified 290 sugar responsive genes, responding rapidly (within 1 h) and specifically to low concentration (1 mM) of glucose, fructose and/or sucrose. For selected genes, the true nature of the signaling sugar molecules and sites of sugar perception were further clarified using non-metabolizable sugar analogues. Using both transgenic and wild-type A. thaliana seedlings, it was shown that the expression of selected sugar-responsive genes was not restricted to a specific tissue or cell type and responded to photoperiod-related changes in sugar availability. This suggested that sugar-responsiveness of genes identified in the cell culture system was not biased toward heterotrophic background and resembled that in whole plants.
  
  
  CONCLUSIONS
  Altogether, our research strategy, using a combination of cell culture and whole plants, has provided an unequivocal evidence for the identity of sugar-responsive genes and the identity of the sugar signaling molecules, independently from their inter-conversions or use for energy metabolism.
authors.affiliation: Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, Umeå, Sweden.
authors.forename: Sabine
authors.initials: S
authors.lastname: Kunz
authors.affiliation: Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, Umeå, Sweden.
authors.forename: Edouard
authors.initials: E
authors.lastname: Pesquet
authors.affiliation: Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, Umeå, Sweden.
authors.forename: Leszek A
authors.initials: LA
authors.lastname: Kleczkowski
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000187:drug effects / Q000235:genetics*; D050260:Carbohydrate Metabolism; D002241:Carbohydrates / Q000494:pharmacology*; D018929:Cell Culture Techniques; D004305:Dose-Response Relationship, Drug; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D017343:Genes, Plant / Q000235:genetics; D036226:Seedlings / Q000166:cytology / Q000187:drug effects / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D002241:Carbohydrates