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Galactose metabolic genes in yeast respond to a ratio of galactose and glucose
- Source :
- Proceedings of the National Academy of Sciences. 112:1636-1641
- Publication Year :
- 2015
- Publisher :
- Proceedings of the National Academy of Sciences, 2015.
-
Abstract
- Natural environments are filled with multiple, often competing, signals. In contrast, biological systems are often studied in "well-controlled" environments where only a single input is varied, potentially missing important interactions between signals. Catabolite repression of galactose by glucose is one of the best-studied eukaryotic signal integration systems. In this system, it is believed that galactose metabolic (GAL) genes are induced only when glucose levels drop below a threshold. In contrast, we show that GAL gene induction occurs at a constant external galactose:glucose ratio across a wide range of sugar concentrations. We systematically perturbed the components of the canonical galactose/glucose signaling pathways and found that these components do not account for ratio sensing. Instead we provide evidence that ratio sensing occurs upstream of the canonical signaling pathway and results from the competitive binding of the two sugars to hexose transporters. We show that a mutant that behaves as the classical model expects (i.e., cannot use galactose above a glucose threshold) has a fitness disadvantage compared with wild type. A number of common biological signaling motifs can give rise to ratio sensing, typically through negative interactions between opposing signaling molecules. We therefore suspect that this previously unidentified nutrient sensing paradigm may be common and overlooked in biology.
- Subjects :
- chemistry.chemical_classification
Cell signaling
Multidisciplinary
Genes, Fungal
Saccharomyces cerevisiae
Mutant
Catabolite repression
Wild type
Galactose
Nutrient sensing
Biological Sciences
Biology
biology.organism_classification
Culture Media
chemistry.chemical_compound
Glucose
Microscopy, Fluorescence
chemistry
Biochemistry
Hexose
Signal Transduction
Subjects
Details
- ISSN :
- 10916490 and 00278424
- Volume :
- 112
- Database :
- OpenAIRE
- Journal :
- Proceedings of the National Academy of Sciences
- Accession number :
- edsair.doi.dedup.....4f1f089b747a23b8be2fb4ca3bec9b6e