Melatonin-AFMK-AMK Cascade as GSH-Independent Thermal Antioxidant Buffer

Coral reefs are dying at alarming rates because rising ocean temperatures cause 'bleaching' — a process where the tiny algae living inside coral cells get expelled, leaving the coral white and starving. These algae (called Symbiodiniaceae) are exquisitely sensitive to heat, and when temperatures spike, their internal chemistry goes haywire. One of the first things to collapse is their supply of glutathione — a workhorse antioxidant molecule that normally mops up the damaging chemical byproducts of stress. Once glutathione crashes, the algae can't protect themselves, and bleaching follows. This hypothesis proposes a surprising rescue mechanism borrowed from an unlikely source: melatonin, the same hormone that helps us sleep. Plants use melatonin as a stress-response chemical, and when it breaks down, it produces a chain of daughter molecules — first AFMK, then AMK — that happen to be potent antioxidants in their own right. The key insight here is that this breakdown cascade might work *independently* of glutathione. So even when the coral algae's normal antioxidant system has already crashed from heat stress, these melatonin-derived molecules could potentially step in as a backup defense, buying the algae — and the coral — critical time to survive a temperature spike. Think of it like a backup generator kicking in when the main power grid fails. If corals and their algae can tap into this melatonin cascade during the moments when heat has already overwhelmed their primary defenses, it could make the difference between bleaching and survival. The idea connects plant stress biology to coral ecology in a way that hasn't been deeply explored — which is both what makes it exciting and why it remains speculative.

This is an AI-generated summary. Read the full mechanism below for technical detail.