Figure 1.

Overview of calcium signalling machinery in fungi. The membrane-bound phosphoinositide-specific phospholipase C (PLC) hydrolyzes phosphatidylinositol-4, 5-bisphosphate (PIP₂) to produce two important second messenger molecules inositol 1,4,5-triphosphates (IP₃) and diacylglycerol (DAG). IP₃ induces Ca²⁺ release from intracellular stores, including mitochondria, Golgi, vacuoles, and endoplasmic reticulum (ER). DAG activates protein kinase C (PKC) that is involved in various signalling processes (Clapham 2007). PLCs also response to different stress signals (Barman et al. 2018). The resting intracellular free Ca²⁺ concentration ([Ca²⁺]_c) is about 100 nM, an increase (shown using arrows pointing upward) of the [Ca²⁺]_c is detected by various Ca²⁺ sensing proteins such as calmodulin (CaM) and NCS-1, which activate specific downstream signalling cascade. Calcineurin-Crz-1 pathway is shown here as an instance of a downstream signalling cascade. Ca²⁺ and CaM activate the serine/threonine phosphatase calcineurin that dephosphorylates the transcription factor Crz-1 for its nuclear location and subsequent expression of target genes in responses to stimuli. Excess Ca²⁺ is removed from the cytosol by Ca²⁺ exchangers (CE) and Ca²⁺ -ATPases (CA) proteins, whereas Ca²⁺ permeable channels (CPC) are required for the influx of extracellular Ca²⁺; and these processes are required to maintain Ca²⁺ homoeostasis in the cell (Tamuli et al. 2013)