**5. Concluding remarks**

In this chapter, we attempted to highlight the studies made in *S. cerevisiae* which correlate the exposure to high concentrations of heavy metals with the Ca2+-mediated cellular responses. *S. cerevisiae* is a very good model to study the cell response to sudden changes of metal concentration in the environment; such studies were greatly facilitated by the ease of obtaining yeast cells expressing aequorin in the cytosol, thus allowing the realtime detection of [Ca2+]cyt fluctuations. By combining Ca2+ monitoring under metal stress with the genetic approaches that make use of mutants with perturbed heavy metal or Ca2+ homeostasis, important aspects related to cell adaptation or cell death under heavy metal stress have been elucidated. Using yeast cells expressing aequorin in the cytosol provides answers regarding the immediate Ca2+-mediated responses, which are crucial for deciding the cell fate. Nevertheless, to understand the Ca2+-mediated cell responses which occur at later phases, developing sensitive Ca2+ sensors targeted to specific compartments is still a desiderate for future studies.
