Dictyostelium becomes multicellular primarily due to:
Transition from unicellular growth to multicellular development is triggered predominantly by starvation for bacterial food and concomitant amino acid limitation. Depletion reduces intracellular energy status, downregulates TOR signaling, activates YakA kinase, and derepresses early developmental genes encoding adenylyl cyclase ACA and cAR1 receptor. Accumulating cAMP pulses then coordinate aggregation. Moisture, predation, or temperature fluctuations do not reliably induce development. Starvation represents ecologically meaningful cue indicating exhaustion of prey, prompting survival strategy
Ref: NCBI Bookshelf, Dictyostelium: Multicellular Development, Starvation response - TOR and early gene induction.
