Pigmentation pathway evolution after whole-genome duplication in fish

Area of Science:

• Evolutionary biology
• Genomics
• Comparative genomics

Background:

• Whole-genome duplications (WGDs) repeatedly shaped vertebrate evolution, but their role in phenotypic diversification is unclear.
• Teleost fishes exhibit exceptional pigmentation diversity and complexity, suggesting unique genetic underpinnings.
• The fish-specific genome duplication (FSGD) is a key evolutionary event in teleost history.

Purpose of the Study:

• Investigate the impact of the FSGD on the evolution of pigmentation pathways in teleost fishes.
• Determine if pigmentation genes were preferentially retained after the FSGD.
• Understand the contribution of FSGD to teleost-specific phenotypic traits, particularly pigmentation.

Main Methods:

• Comparative genomic analysis of 128 vertebrate pigmentation genes across five teleost genomes.
• Phylogenetic and synteny analyses to reconstruct gene evolution post-FSGD.
• Comparison of duplicate gene retention rates in pigmentation pathways versus the genome-wide average.

Main Results:

• Pigmentation genes show significantly higher retention rates post-FSGD in teleosts compared to tetrapods (30% more genes).
• Key components of the melanocyte regulatory network were retained as duplicates.
• Retained duplicated genes often preserve protein complex stoichiometries and are enriched for developmental functions.

Conclusions:

• The FSGD has been a major driver of teleost-specific pigmentation complexity and diversity, including novel pigment cell types.
• Species-specific differences in duplicate gene retention contribute to the wide range of teleost color patterns.
• WGDs, like the FSGD, are crucial for increasing complexity and diversity in vertebrate phenotypic evolution.