Molecular Evolution of clock Genes in Vertebrates

Area of Science:

• Evolutionary Biology
• Genomics
• Chronobiology

Background:

• Circadian rhythms regulate daily life activities and are controlled by critical genes like Circadian locomotor output cycle kaput (Clock).
• Understanding the evolutionary history of the clock gene family is crucial for comprehending biological rhythm regulation across species.

Purpose of the Study:

• To elucidate the evolutionary history of the clock gene family in a diverse range of vertebrates.
• To provide novel insights into the evolution of clock genes using a comprehensive genomic analysis.

Main Methods:

• Genome-wide analysis of 102 vertebrate genomes to identify clock gene sequences.
• Syntenic analysis to confirm gene conservation and duplication events.
• dN/dS analysis to investigate the evolutionary fates of duplicated clock genes.

Main Results:

• Identified 264 clock sequences across 102 vertebrate genomes.
• Observed two clock isotypes (clock1 and clock2) in lobe-finned and basal ray-finned fishes, with most teleosts possessing three (two clock1, one clock2) due to whole-genome duplication.
• Confirmed conservation of clock1a, clock1b, and clock2 in teleosts, noted two clock2 genes in osteoglossomorph fishes, and found CLOCK protein variations in N-terminal and poly Q regions.
• dN/dS analysis indicated distinct evolutionary paths for duplicated clock genes in lobe-finned versus ray-finned fish.

Conclusions:

• The study provides a genome-wide perspective on clock gene evolution in vertebrates.
• Gene duplication events, particularly whole-genome duplication in teleosts, have shaped the clock gene family.
• Distinct evolutionary pressures on clock genes suggest clade-specific adaptations in biological rhythm regulation.