The timing of Timezyme diversification in vertebrates

Area of Science:

• Evolutionary Biology
• Genomics
• Chronobiology

Background:

• Melatonin synchronizes vertebrate biological functions with environmental cycles.
• Arylalkylamine N-acetyl transferase (AANAT) regulates melatonin production and is key to understanding its evolution.
• The evolutionary origins of diverse vertebrate AANAT isoforms remain unclear.

Purpose of the Study:

• To investigate the role of whole genome duplications (WGDs) in the diversification of the AANAT gene family across vertebrates.
• To trace the evolutionary history and duplication events of AANAT genes.

Main Methods:

• Phylogenetic analysis of AANAT genes.
• Synteny analysis to examine gene order and conservation.
• Comparative genomics utilizing available vertebrate genome sequences.

Main Results:

• The AANAT1/2 duplication predates the divergence of Actinopterygii and Sarcopterygii.
• A secondary loss of AANAT2 occurred in Sarcopterygii.
• Teleost-specific WGD likely generated AANAT1a/1b and AANAT2/2' paralogs, with AANAT2' lost early in ray-finned fish.
• Subsequent secondary losses of AANAT isoforms (AANAT1a, AANAT1b) occurred in specific fish lineages (Paracantopterygii, Ostariophysi).
• Salmonids exhibit further AANAT diversity potentially due to their own WGD and subsequent losses.

Conclusions:

• Vertebrate AANAT diversity is shaped by three ancestral WGDs followed by extensive, previously uncharacterized secondary gene losses.
• Extant AANAT isoforms display subfunctionalization in localization, enzyme activity, and affinity, evolving over time.
• This study clarifies the evolutionary history of AANAT, crucial for understanding melatonin's role in vertebrate circadian and seasonal rhythms.