| Description: | It has been strongly argued that plant cells should have a means of sensing sugars at the cell surface, so that extracellular and intracellular sugars can be sensed separately and their metabolism coordinated (Lalonde et al., Plant Cell, 11, 707-26, 2000). There is good evidence for an intracellular hexokinase-dependent pathway of hexose sensing in plants, but very little evidence for a hexokinase-independent signalling pathway, such as that provided by SNF3 or RGT2 in yeast. Many papers on sugar sensing in plants cite work from two laboratories as evidence for hexokinase-independent hexose signalling in plants. The first is that in which cell-wall invertase and sucrose synthase genes were induced by treatment of a Chenopodium suspension culture with 30 mM 6-Deoxyglucose (6DOG) for 24 h (Roitsch et al., Plant Physiol 108, 285-294, 1995; Godt et al., J. Plant Physiol 146, 231-238, 1995). The second is that in which a patatin transgene in Arabidopsis was shown to be weakly induced by growth over several days on a mixture of 30 mM glucose plus 30 mM 3-O-methylglucose (3OMG), but strongly induced by growth on 30 mM Glc plus 90 mM 3OMG (Martin et al., Plant J, 11, 53-62, 1997). We are not aware of any examples of Arabidopsis genes which respond to 6DOG or 3OMG yet this is an area of wide significance. Identification of such a gene would help to establish if a hexokinase-independent signalling system operates in plants, and would provide a basis for establishment of a genetic screen for mutants, using the gene promoter linked to a reporter such as luciferase. The aim of this proposal is to discover any genes which are either activated or repressed by glucose AND by 3OMG and/or 6DOG, but not by mannitol (an osmotic control). The use of both 3OMG and 6DOG will help to identify non-specific effects of either. All substrates will first be analysed by HPLC to confirm that they are pure. Arabidopsis Col-0 seedlings will be grown in vitro for 7 days in the absence of sugars, then treated with 30 mM glucose or glucose analogue for 8 h (these conditions are based on concentrations and time courses of Roitsch et al.). RNA will then be isolated from multiple independent plates to minimise biological variation. |
NASCArrays Information at The BAR
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