pH Modulation in Fungal Pathogenicity

Fungal pathogens employ sophisticated mechanisms to sense and manipulate pH in their environment, thereby facilitating host colonisation, nutrient acquisition and evasion of plant or animal defences. Central to this process is the ability to alter ambient pH through secretion of organic acids or ammonia, creating conditions that optimise the activity of virulence factors such as cell-wall-degrading enzymes and secondary metabolites. At the molecular level, ambient pH is transduced via conserved signalling pathways—most notably the Pal/Rim pathway and its downstream transcription factor PacC (also known as Rim101)—which govern the expression of genes involved in acid or alkaline adaptation. In parallel, fluctuations in cytosolic pH modulate intracellular signalling cascades, including mitogen-activated protein kinases (MAPKs), to reprogramme cellular processes such as hyphal chemotropism, cell-wall remodelling and stress responses. Collectively, these strategies enable fungal pathogens to tailor host microenvironments, switch between biotrophic and necrotrophic lifestyles and overcome nutritional or oxidative stresses. Understanding pH-modulation mechanisms has profound implications for agriculture and medicine, as it reveals targets for novel antifungal agents and informs the development of resistant cultivars or biocontrol approaches.

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pH Modulation in Fungal Pathogenicity publication trend

The graph below shows the total number of articles in ph modulation in fungal pathogenicity across all publications each year (not limited to Nature Index journals).

Technical terms

Ambient pH: The extracellular hydrogen-ion concentration in the immediate environment of a fungus, which influences enzyme activity and gene expression.

PacC/Rim101 pathway: A conserved signal transduction cascade that senses extracellular pH and activates a pH-responsive transcription factor governing adaptation to acidic or alkaline conditions.

Cytosolic pH: The internal hydrogen-ion concentration within the fungal cell, which serves as a regulator of intracellular signalling and metabolic pathways.

Mitogen-activated protein kinase (MAPK): A family of protein kinases that transduce environmental and developmental cues to regulate cellular responses, including stress adaptation and morphogenesis.

Hyphal chemotropism: Directional growth of fungal hyphae towards chemical gradients, a process essential for host tissue penetration and nutrient foraging.

References

1. Cytosolic pH Controls Fungal MAPK Signaling and Pathogenicity. mBio (2023).
2. VmPacC-mediated pH regulation of Valsa mali confers to host acidification identified by comparative proteomics analysis. Stress Biology (2023).
3. The pH-Responsive Transcription Factor PacC Governs Pathogenicity and Ochratoxin A Biosynthesis in Aspergillus carbonarius. Frontiers in Microbiology (2020).
4. Environmental pH modulation by pathogenic fungi as a strategy to conquer the host. PLOS Pathogens (2017).