Transcriptomic and metabolomic insights into light-mediated unicellular-to-multicellular transition in Dictyostelium discoideum.

Dictyostelium discoideum is a social amoeba that transitions from unicellular to multicellular forms in response to environmental signals, making it an intriguing model for studying cell aggregation and differentiation. Although previous studies have demonstrated that Dictyostelium slugs exhibit phototaxis, the mechanisms behind light-induced developmental changes remain unclear. In this study, we investigated how light triggers the transition to multicellularity and its associated metabolites and genes. Our findings revealed that spore yield depends on light exposure, with slower multicellular development under dark incubation. Transcriptomics analysis on QS9 amoebae identified upregulation of small GTPases such as rasD and racL in response to light, which likely promote cell movement, phagocytosis and actin protrusions. Light also enhanced cAMP production, driving the aggregation, post-aggregation and development of single cells. Additionally, c-di-GMP was essential for cell differentiation during multicellular growth and was upregulated by light. Metabolomic analysis on QS9 amoebae revealed that the downregulation of LPC (lysophosphatidylcholine) was detected under both unicellular and multicellular phases. Moreover, reduced levels of GSH (glutathione) in dark may impede multicellular structures of D. discoideum. These findings provide insights into light-triggered cell differentiation and pattern formation, offering a better understanding of molecular mechanisms underlying the transition to multicellularity in Dictyostelium cells.