Abstract
Calcium (Ca(2+)), a critical secondary messenger, is also known as the molecule of life and death. The cell responds to a minute change in Ca(2+) concentration and tightly maintains Ca(2+) homeostasis. Therefore, determining the cell Ca(2+) level is critical to understand Ca(2+) distribution in the cell and various cell processes. Many techniques have been developed to measure Ca(2+) in the cell. We review here different methods used to detect and measure Ca(2+) in filamentous fungi. Ca(2+)-sensitive fluorescent chlortetracycline hydrochloride (CTC), Ca(2+)-selective microelectrode, Ca(2+) isotopes, aequorins, and RGECOs are commonly used to measure the Ca(2+) level in filamentous fungi. The use of CTC was one of the earliest methods, developed in 1988, to measure the Ca(2+) gradient in the filamentous fungus Neurospora crassa. Subsequently, Ca(2+)-specific microelectrodes were developed later in the 1990s to identify Ca(2+) ion flux variations, and to measure Ca(2+) concentration. Another method for quantifying Ca(2+) is by using radio-labeled Ca(2+) as a tracer. The usage of (45)Ca to measure Ca(2+) in Saccharomyces cerevisiae was reported previously and the same methodology was also used to detect Ca(2+) in N. crassa recently. Subsequently, genetically engineered Ca(2+) indicators (GECIs) like aequorins and RGECOs have been developed as Ca(2+) indicators to detect and visualize Ca(2+) inside the cell. In this review, we summarize various methodologies used to detect and measure Ca(2+) in filamentous fungi with their advantages and limitations. •Chlortetracycline (CTC) fluorescence assay is used for visualizing Ca(2+) level, whereas microelectrodes technique is used to determine Ca(2+) flux in the cell.•Radioactive (45)Ca is useful for quantification of Ca(2+) in the cellular compartments.•Genetically modified calcium indicators (GECIs) are used to study Ca(2+) dynamics in the cell.