Calcium imaging: a technique to monitor calcium dynamics in biological systems

Calcium ion (Ca²⁺) is a multifaceted signaling molecule that acts as an important second messenger. During the course of evolution, plants and animals have developed Ca²⁺ signaling in order to respond against diverse stimuli, to regulate a large number of physiological and developmental pathways. Our understanding of Ca²⁺ signaling and its components in physiological phenomena ranging from lower to higher organisms, and from single cell to multiple tissues has grown exponentially. The generation of Ca²⁺ transients or signatures for various stress factor is a well-known mechanism adopted in plant and animal systems. However, the decoding of such remarkable signatures is an uphill task and is always an interesting goal for the scientific community. In the past few decades, studies on the concentration and dynamics of intracellular Ca²⁺ are significantly increasing and have become a trend in modern biology. The advancement in approaches from Ca²⁺ binding dyes to in vivo Ca²⁺ imaging through the use of Ca²⁺ biosensors to achieve spatio-temporal resolution in micro and milliseconds range, provide us phenomenal opportunities to study live cell Ca²⁺ imaging or dynamics. Here, we describe the usage, improvement and advancement of Ca²⁺ based dyes, genetically encoded probes and sensors to achieve extraordinary Ca²⁺ imaging in plants and animals.