Melatonin-Induced Diatoxanthin NPQ Buffer in Symbiodiniaceae

Coral reefs depend on a partnership: the coral animal hosts millions of microscopic algae (called Symbiodiniaceae) that live in its tissues and provide food through photosynthesis. When ocean temperatures rise, this partnership breaks down — the algae get stressed, produce toxic byproducts, and get expelled, leaving the coral bleached white and dying. Scientists are racing to understand what might protect these algae from heat stress before it's too late. This hypothesis proposes a surprising link between two seemingly unrelated fields. Melatonin — yes, the same hormone that helps you sleep — also acts as a stress-response molecule in plants, helping them cope with harsh conditions. Separately, many photosynthetic organisms have a built-in sunscreen system: when there's too much light or heat, special pigments called diatoxanthin can be rapidly produced (from a precursor called diadinoxanthin) to safely absorb and dissipate excess energy before it damages the cell. The idea here is that melatonin might act as a chemical trigger in coral's algae, activating this pigment-based protection system and giving the algae a better shot at surviving thermal stress. If melatonin can flip on this molecular sunscreen in Symbiodiniaceae, it could be a key part of how some corals naturally cope with warming waters — and potentially a lever scientists could use to help vulnerable reefs.

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