When individual amoebae of the slime mold Dictyostelium discoideumface hard times, up to 100,000 of them form a multicellular aggregate. Because spores, which ultimately form from this aggregate, are unable to move, the timing of sporulation is critical for the successful completion of Dictyostelium's life cycle. On , Anjard, Su and Loomis identify novel players in the regulation of this event. Previously,these authors had identified the peptide SDF-2 as a sporulation regulator, and had proposed that GABA triggers SDF-2 production by binding to the G-protein-coupled receptor (GPCR) GrlE. Now, they establish that GrlE is probably linked to the Gα7 subunit. Intriguingly, they also find that cells mutant for the GPCR GrlA and the Gα4 subunit fail to accumulate SDF-2 in response to GABA. Finally, the authors identify the steroid SDF-3 as a sporulation factor and suggest that it signals through GrlA and Gα4 to elicit the rapid release of GABA, placing it at the top of the sporulation-inducing cascade.
