Light-entrained chromatin priming poises rapid metamorphosis in a marine sponge.

Diminishing light at sunset is associated with extensive chromatin remodelling in swimming Amphimedon queenslandica larvae before settlement, despite relatively modest gene-expression changes.

• Why it matters: Planetary cues like light must coordinate with local ecological signals to prime the genome for rapid larval-to-juvenile reprogramming, but the mechanism is poorly understood.
• What they did: The study integrated time-resolved transcriptomics and chromatin accessibility profiling across larval competence, settlement, and early metamorphosis in Amphimedon queenslandica, including constant-light and sunset conditions.
• The result: Constant light prevented from experiencing sunset fails to settle and is linked to widespread loss of chromatin accessibility and repression of competence-associated TFs, including CLOCK, enabling an anticipatory permissive chromatin landscape for rapid transcriptional reprogramming.