Altered morphogenesis of Saccharomyces cerevisiae isw2 mutant alpha cells is caused by the autocrine activation of the mating pathway.
Petra Trachtulcova, Ivana Frydlova, Ivana Malcova-Janatova, Jiri Hasek
Lab.Cell Reproduction, Institute of Microbiology ASCR, Videnska 1083, Prague 4, 14220, Czech Republic
The absence of the Isw2p-Itc1p chromatin-remodeling complex in Saccharomyces cerevisiae causes derepression of MAT a-specific genes resulting in autocrine activation of the pheromone response pathway in MAT alpha cells. Due to these defects alpha cells of the originally non-invasive strain display invasive growth and various morphological aberrations. Here we show that the morphological aberrations of MAT alpha cells of the isw2 deletion mutant are associated with altered distribution of chitin, cell wall forming protein Bni4 and septin Cdc12. In these cells, chitin was accumulated in enlarged rings and belts. The Bni4-GFP and Cdc12-GFP fusions were localized to bud necks and to the cortical domain of malformations in a similar way as observed in mating projections of wild-type cells. Moreover, Bni4-GFP was arranged into filaments in the unbudded cells. To analyze the effect of the activated pheromone response pathway we prepared the isw2ste4 double deletion mutant. Both, MAT a and MAT alpha cells of this double mutant, did not show any aberration described above. We suggest that the altered morphogenesis of MAT alpha cells of the isw2 deletion mutant is caused by the autocrine activation of the pheromone response pathway during vegetative growth. This work was supported by grants GAAV A5020102, IAA5020409 and IRC AVOZ50200510.