Sexual pheromone modulates the frequency of cytosolic Ca 2+ bursts in Saccharomyces cerevisiae

TARKOWSKI, N; AGUILAR, P; PONCE DAWSON, S; CARBÓ, N

Cordoba Capital

Congreso; LII Reunión Anual SAIB 2016; 2016

Universidad Nacional de Cordoba

Transient and highly regulated elevations of cytosolic Ca2+ control a variety of cellular processes. In budding yeast, Ca2+ has been implicated in the response to several environmental challenges. Bulk measurements using radioactive Ca2+ and the luminescent sensor aequorin have shown that in response to pheromone, yeast cells experience a rise of cytosolic Ca2+ that is mediated by two import systems composed by the Mid1-Cch1-Ecm7 protein complex, and the Fig1 protein. Although this response has been largely studied, there is no report on Ca2+ dynamics at the single cell level. Here, we adapted protein calcium indicators to yeast and show that both vegetative and pheromone-treated cells exhibit discrete and asynchronous Ca2+ bursts. Most bursts reach maximal amplitude in 1-10 secs, span between 7 and 30 secs and decay fitting a single exponential model. In vegetative cells bursts are scarce but preferentially occur when cells are transitioning G1 and S phase. Upon pheromone presence Ca2+ burst occurrence increases dramatically, persisting during cell growth polarization. Pheromone concentration modulates burst frequency in a mechanism that depends on Mid1, Fig1 and a third, still unidentified, import system.