Analysis of cytosolic calcium burst of Saccharomyces cerevisiae during the response to the sexual pheromone

TARKOWSKI, NAHUEL; PONCE DAWSON, SILVINA; AGUILAR, PABLO S.

Mendoza

Congreso; LVIII SAIB Annual Meeting; 2022

SAIB

Saccharomyces cerevisiae constitutes an ideal system in which to study cell signaling mechanisms generating results that can often be extrapolated to other eukaryotes (Botstein, Chervitz, and Cherry 1997; Engelberg, Perlman, and Levitzki 2014; Khurana et al. 2015). S. cerevisiae haploid cells of are of particular interest since they respond to the sexual pheromone secreted by cells of the opposite sexual type,generating a sequence of events that leads to cell cycle arrest and subsequent morphological changes, such as cell polarization, interaction and fusion with a mating partner (Dohlman and Slessareva 2006). Previous studies have shown that calcium incorporation during pheromone response was necessary to coordinate genes involved in signal transduction and cell survival (Aguilar, Engel, and Walter 2007; Iida,Yagawa, and Anraku 1990; Muller et al. 2003). We have previously adapted the fluorescent calcium sensor GCaMP6f in yeast. Through in vivo fluorescence microscopy experiments followed by single cell segmentation and fluorescencequantification, we showed that the pheromone does not generate, as previously reported, a single continuous increase in cytosolic calcium levels, but transient increases in bursts of short duration (Carbó- Tarkowski et al., 2017). Likewise, the presence of the pheromone seems to translate into an increase in the frequency of appearance of these calcium bursts, suggesting that the information transmitted bycalcium is encoded in the temporal distribution of these bursts. Here, analyzing strains that are deficient in each known calcium flux pathway we show that the calcium response not only depends on transport from the extracellular medium, but it can also depend on intracellular calcium flow pathways. Moreover, we discovered that Yvc1 also plays an important role in this response suggesting the existence of acalcium-induced calcium release system in this organism. Modeling of cytosolic and vacuolar calcium dynamics enabled us to assign specific features to the different calcium pathways which explained part of our experimental results.