Melatonin Synthesis and Function: Evolutionary History in Animals and Plants

Area of Science:

• Biochemistry
• Evolutionary Biology
• Cell Biology

Background:

• Melatonin is a molecule with ancient origins, likely first functioning as a free radical scavenger in bacteria.
• Endosymbiotic theory suggests that mitochondria and chloroplasts, derived from bacteria, retained the ability to produce melatonin.
• This ancient antioxidant function persists in modern organisms, with additional complex roles emerging later in evolution.

Purpose of the Study:

• To trace the evolutionary origins and early functions of melatonin.
• To elucidate the role of melatonin synthesis in organelles like mitochondria and chloroplasts.
• To compare the diverse functions and synthetic pathways of melatonin in animals and plants.

Main Methods:

• Comparative analysis of melatonin's presence and function across different taxa, from bacteria to plants and animals.
• Review of evolutionary biology principles, including the endosymbiotic theory.
• Examination of biochemical pathways for melatonin synthesis in various organisms.

Main Results:

• Melatonin synthesis is conserved in mitochondria (animals, plants) and chloroplasts (plants), originating from early bacterial endosymbionts.
• Melatonin's primary ancient role is as an antioxidant, a function retained across all life forms.
• In animals, melatonin regulates sleep, circadian rhythms, and immunity; in plants, it influences growth, stress resistance, and stomatal closure.

Conclusions:

• Melatonin's ancient antioxidant role, established in bacteria and retained in organelles, is fundamental to its biological significance.
• The evolution of melatonin involved the development of receptor-mediated functions, leading to diverse physiological roles in animals and plants.
• Understanding melatonin's evolutionary trajectory provides insights into its multifaceted importance in health and stress response across the tree of life.