In the presence of a non-fermentable carbon source, nitrogen-starved diploid cells of the yeast Saccharomyces cerevisiae undergo a meiotic program called sporulation to form gametes called spores. While four spores are produced under standard laboratory sporulation conditions, spore number is known to be regulated by carbon availability: under carbon-depleted conditions, yeast cells package a portion of the four haploid meiotic nuclei into spores. Our lab has demonstrated that these unpackaged meiotic products undergo programmed nuclear destruction (PND) that is associated with apoptotic-like DNA fragmentation. Nevertheless, the mechanism that mediates PND remained to be elucidated. Here, I describe the execution of PND through an unusual form of autophagy that has not been documented previously in yeast. This form of autophagy is most similar to megaautophagy in plants and lysosomal membrane permeabilization in mammals. My results demonstrate further diversity in cell death programs in unicellular microbes that is potentially conserved across eukaryotes.

In the presence of a non-fermentable carbon source, nitrogen-starved diploid cells of the yeast Saccharomyces cerevisiae undergo a meiotic program called sporulation to form gametes called spores. While four spores are produced under standard laboratory sporulation conditions, spore number is known to be regulated by carbon availability: under carbon-depleted conditions, yeast cells package a portion of the four haploid meiotic nuclei into spores. Our lab has demonstrated that these unpackaged meiotic products undergo programmed nuclear destruction (PND) that is associated with apoptotic-like DNA fragmentation. Nevertheless, the mechanism that mediates PND remained to be elucidated. Here, I describe the execution of PND through an unusual form of autophagy that has not been documented previously in yeast. This form of autophagy is most similar to megaautophagy in plants and lysosomal membrane permeabilization in mammals. My results demonstrate further diversity in cell death programs in unicellular microbes that is potentially conserved across eukaryotes.