Glucose signaling through nuclear hexokinase1 complex in Arabidopsis

Arabidopsis hexokinase1 (HXK1) is a glucose sensor that regulates gene expression and plant growth and development. We have previously developed a high glucose (6%) assay based on the seedling developmental arrest to isolate and characterize the glucose-insensitive (gin) mutants. The analysis of gin2 as a null HXK1 mutant has revealed that the regulatory functions of HXK1 are distinct from its conventional role in glycolysis. In the Nov 3rd issue of Cell, we presented a new insight into the mechanism of HXK1-dependent glucose signaling. By combining proteomic and binary interaction screens, we discover two HXK1 unconventional partners (HUPs). HXK1 and HUPs form a core complex in the nucleus and directly regulate glucose-responsive gene expression and plant growth. As the 6% glucose assay is complicated by additional osmotic stress and nitrate signals, we have tested the gin2 and hup mutants using the 2% glucose assay. We believe that the new and more physiological glucose assay could help us better dissect the molecular mechanisms that link glucose regulation to diverse plant signaling pathways. Further functional analysis of gin mutants and the components in the novel nuclear HXK1 complex will provide more comprehensive mechanistic understanding of glucose sensing and signaling in plants.