A Complex Mode of Glucose Signaling

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Science  17 Nov 2006:
Vol. 314, Issue 5802, pp. 1051
DOI: 10.1126/science.314.5802.1051c

In Arabidopsis, hexokinase 1 (HXK1) acts a glucose sensor to regulate gene expression and plant growth, which is a role far removed from its function in glycolysis. However, the mechanisms whereby HXK1 mediates glucose signaling have been unclear. After showing that a small fraction of Arabidopsis HXK could be found in the nucleus, Cho et al. used proteomic and two-hybrid screens to identify two proteins—vacuolar H+-ATPase B1 (VHA-B1) and the 19S regulatory particle of proteasome subunit (RPT5B)—as nucleus-specific HXK1-interacting partners that formed a complex with HXK1. Genetic analysis revealed that vha-B1 and rpt5b loss-of-function mutants resembled the HXK1 gin2 (glucose-insensitive 2 mutant): All three mutants were insensitive to repression of cotyledon expansion, chlorophyll accumulation, and leaf and root development by high glucose and showed growth retardation as compared to wild-type plants under low-light low-nutrient conditions. Like gin2, the vha-B1 and rpt5b mutants did not exhibit glucose-mediated repression of the chlorophyll a/b—binding protein (CAB) and carbonic anhydrase (CAA) genes. Chromatin immunoprecipitation analysis showed that the HXK1 complex bound to the CAB2 promoter; this binding was reduced but not abolished in the vha-B1 and rpt5b mutants. Thus, these three proteins appear to form a complex that functions in the glucose-mediated regulation of gene transcription. — EMA

Cell 127, 579 (2006).

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