Ca²⁺ Imaging in Plants Using Genetically Encoded Yellow Cameleon Ca²⁺ Indicators

Abstract

Temporally and spatially defined changes in cellular calcium (Ca²⁺) concentration represent stimulus-specific signals and regulate a myriad of biological processes. The development of ratiometric Ca²⁺ reporter proteins like Yellow Cameleons (YCs) has greatly advanced our ability to analyze Ca²⁺ dynamics in vivo with unprecedented spatial and temporal resolution. In plants, the application of these Ca²⁺ reporter proteins has been pioneered for the investigation of Ca²⁺ dynamics in guard cells, and recently their use has been extended to other single-cell models like growing pollen tubes and root hairs. However, in plants, the use of YC reporter proteins has largely remained restricted to the investigation of cytoplasmic alterations of Ca²⁺ concentrations. Here, we provide an introduction to current methods for imaging Ca²⁺ dynamics with increasing sophistication.