Autophagy of the somatic stalk cells nurses the propagating spores of Dictyostelid social amoebas

Background: Autophagy (self-feeding) assists survival of starving cells by partial self-digestion, while dormancy as cysts, spores or seeds enables long-term survival. Starving Dictyostelium amoebas construct multicellular fruiting bodies with and stalk cells, many Dictyostelia still able to encyst individually like their single-celled ancestors. While autophagy mostly occurs in the somatic gene knock-outs Dictyostelium discoideum (D. discoideum) formed no lacked cAMP induction prespore expression. Methods: To investigate whether also prevents encystation, we knocked-out genes atg5 atg7 dictyostelid Polysphondylium pallidum, which forms both cysts. We measured spore cyst differentiation viability knock-out well expression its regulation cAMP. tested a hypothesis that require materials derived from cells. Sporulation requires secreted acting on receptors intracellular PKA. compared morphology developed induced single stimulation 8Br-cAMP, membrane-permeant PKA agonist. Results: Loss P. pallidum reduced but did not prevent encystation. However, spore, differentiation, cAMP-induced were lost. Spores in vitro 8Br-cAMP smaller rounder than multicellularly they lysed detergent germinate, unlike spores. Conclusions: The stringent requirement sporulation multicellularity autophagy, suggests nurse through autophagy. This highlights major cause for cell evolution early multicellularity.