CONTRIBUTIONS OF KNOWN PATHWAYS TO CALCIUM BURST DURING THE PHEROMONE RESPONSE

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

VIRTUAL

Congreso; LVII SAIB Annual Meeting - XVI SAMIGE Meeting (virtual); 2021

The mating pheromones secreted by haploid cells of Saccharomyces cerevisiae indicate the presence of cells of one mating type to those of the opposite mating type. This initiates a sequence of events, which includes cellular arrest and growth polarization toward the potential partner cell. Different reports have shown that during the response to the sexual pheromone,S. cerevisiae incorporates calcium from the extracellular environment (Iida et al., 1994; Muller et al., 2001; Muller et al., 2003). These evidences were obtained by measuring the incorporation of radioactive calcium or the use of the luminescent probe aequorin in bulk cell populations. Monitoring the GCaMP6f fluorescent sensor by microscopyin single cells, we showed that the pheromone does not generate a single increase in cytosolic ca2 + levels but rather transient increases in the form of bursts (Carbó-Tarkowskiet al., 2017). Our results suggest that the information transmitted by calcium is encoded in the temporal distribution of these bursts. The mating pheromone stimulates at least two pathways of calcium entry, a high-affinity calcium influx system (HACS) and a low-affinity calcium influx system (LACS). We have proposed that the calcium response not only depends on transport pathways from the extracellular medium, but it can also depend on each of the different calcium flow pathways to and from each of the internal reservoirs. To address this hypothesis, we are currently studying the role of calcium transporters in internal reservoirs during response to pheromone through the GCaMP6f sensor. For this, we monitored cytosolic calcium dynamics during the pheromone responsein different mutants lacking key calcium intracellular transporters: the vacuolar ATPase Pmc1, the vacuolar membrane Ca2+/H+antiporter with Vcx1, the vacuolar membrane exporter Yvc1 and the GolgiCa2+/Mn2+ P-type ATPase Pmr1.