HowSaccharomycesResponds to Nutrients

Abstract

Yeast cells sense the amount and quality of external nutrients through multiple interconnected signaling networks, which allow them to adjust their metabolism, transcriptional profile and developmental program to adapt readily and appropriately to changing nutritional states. We present our current understanding of the nutritional sensing networks yeast cells rely on for perceiving the nutritional landscape, with particular emphasis on those sensitive to carbon and nitrogen sources. We describe the means by which these networks inform the cell's decision among the different developmental programs available to them-growth, quiescence, filamentous development, or meiosis/sporulation. We conclude that the highly interconnected signaling networks provide the cell with a highly nuanced view of the environment and that the cell can interpret that information through a sophisticated calculus to achieve optimum responses to any nutritional condition.

Life in the midst of scarcity: adaptations to nutrient availability in Saccharomyces cerevisiae

“…For S. cerevisiae cells, the constantly fluctuating nutrient content of the environment is a key determinant of cell cycle progression and growth, stress resistance and metabolism. The nutrient-induced signalling network enables yeast both to optimally profit from rich nutrient conditions by stimulating cell proliferation and to survive periods of nutrient scarceness by inducing the entry into a quiescent, resting phase, called the stationary phase (G 0 ) Roosen et al 2004;Zaman et al 2008). In general, a nutrient is sensed by the signalling network (i) externally, via a receptor protein in the plasma membrane, which after binding of the nutrient adopts a new conformation that activates a downstream signalling cascade, or (ii) internally, after uptake of the nutrient, possibly followed by its metabolism, thereby causing a change in its intracellular concentration which, in turn, modulates downstream signalling (Forsberg and Ljungdahl 2001;Holsbeeks et al 2004).…”

Hap2-3-5-Gln3 determine transcriptional activation of GDH1 and ASN1 under repressive nitrogen conditions in the yeast Saccharomyces cerevisiae

“…The response of Saccharomyces cerevisiae to nutrient limitation is a model whose study has amply contributed to our knowledge of the mechanisms determining transcriptional activation (Zaman et al, 2008). Nutrient limitation results in a complex adaptation of the physiology of yeast cells, which allows them to redefine their transcription programme.…”

“…This leads to the activation of particular sets of genes, whose products are needed to evoke an appropriate physiological response. Transcriptional activators are composed of a DNA-binding domain, which targets these proteins to specialized binding sites, and an activation domain that mediates transcription initiation; these two domains can be contained in single or different polypeptides (Zaman et al, 2008).When yeast cells are provided with poor nitrogen sources, such as proline, genes coding for enzymes involved in the catabolism of these compounds are highly expressed. Conversely, in the presence of high-quality nitrogen sources such as glutamine, a decrease in the levels of catabolic enzymes is observed.…”

LncRNAs: Bridging environmental sensing and gene expression

“…39 This switch involves reprogramming of upwards of 40% of the yeast transcriptome as a result of derepression and transcriptional activation of genes necessary for metabolism of sugars other than glucose. 40,41 A key component of the glucose to galactose metabolic switch is the GAL gene cluster consisting of GAL1, GAL10, and GAL7. These genes exist in 3 distinct transcriptional states depending on the carbon source in the media.…”