Osmotic Stress Signaling in Saccharomyces Cerevisiae

Osmotic stress is a fundamental environmental challenge for yeast and triggers a conserved signalling cascade centring on the High Osmolarity Glycerol (HOG) pathway. This cascade is initiated through sensory branches that detect changes in external osmolarity and converge on the MAP kinase Hog1. Activation of Hog1 orchestrates rapid adjustments in gene expression, metabolic fluxes and cell‐cycle progression. One key adaptation is the accumulation of glycerol as a compatible solute, preventing water efflux and conserving turgor pressure. In addition to glycerol, alternative osmolytes such as trehalose may contribute under specific metabolic states. Signalling through HOG is modulated by feedback loops, crosstalk with other stress pathways and interactions with mitochondrial function via retrograde signalling. Together, these mechanisms ensure robustness and flexibility, enabling yeast to survive both static and dynamic osmotic challenges in natural and industrial settings.

Research from Nature Portfolio

Recent studies have illuminated the molecular dynamics of Hog1 activation, revealing that phosphorylation of Hog1 by its upstream kinase Pbs2 can alternate between distributive and processive modes under the control of a positive feedback loop. Direct phosphorylation of Pbs2 by Hog1 on a regulatory serine residue enhances affinity between the kinases, fine‐tuning sensitivity and robustness to osmotic perturbations. This mixed mechanism ensures both ultrasensitivity and adaptability across a range of osmotic stresses. Another investigation has demonstrated that the carbon source profoundly influences osmoadaptation. Yeast respiring ethanol exhibit HOG pathway activation comparable to glucose‐grown cells but accumulate trehalose rather than glycerol, revealing a metabolic rerouting that preserves redox balance during respiration. These findings underscore the interplay between central metabolism and osmotic signalling, with implications for fermentative and respiratory growth modes.

Osmotic Stress Signaling in Saccharomyces Cerevisiae publication trend

The graph below shows the total number of articles in osmotic stress signaling in saccharomyces cerevisiae across all publications each year (not limited to Nature Index journals).

Technical terms

High Osmolarity Glycerol (HOG) pathway: A conserved mitogen‐activated protein kinase cascade that senses and responds to hyperosmotic stress by promoting protective adaptations.

Mitogen‐activated protein kinase (MAPK): A phosphorylation‐activated enzyme that transmits signals through cascades to regulate cellular processes.

Compatible solute (osmolyte): A small organic molecule, such as glycerol or trehalose, that accumulates to counteract osmotic imbalance without disrupting cellular functions.

Processive phosphorylation: A mechanism in which a kinase phosphorylates multiple sites on its substrate in a single binding event.

Retrograde (RTG) signalling: Communication from mitochondria to the nucleus that adjusts gene expression in response to mitochondrial status.

References

1. Positive feedback induces switch between distributive and processive phosphorylation of Hog1. Nature Communications (2023).
2. The yeast osmostress response is carbon source dependent. Scientific Reports (2017).
3. Yeast cell responses and survival during periodic osmotic stress are controlled by glucose availability. eLife (2024).
4. Natural variation in yeast reveals multiple paths for acquiring higher stress resistance. BMC Biology (2024).
5. Inactivation of HAP4 Accelerates RTG-Dependent Osmoadaptation in Saccharomyces cerevisiae. International Journal of Molecular Sciences (2023).