Practice question

Dictyostelium aggregation field size is regulated by autocrine factor called counting factor, identified as smlA secreted glycoprotein complex. It functions as quorum sensor: secreted by starving cells, concentration proportional to cell density modulates adhesion and motility via altering gene expression of adhesion molecules and myosin. High counting factor promotes breakup of streams into smaller aggregates; low promotes larger mounds. Mutants lacking smlA form abnormally large aggregates that produce oversized fruiting bodies, while overexpression yields tiny aggregates. Hence smlA regulates aggregate size ensuring optimal spore-stalk ratio and efficient dispersal rather than directly controlling motility or germination per se.