Subgenome Partitioning and Polyploid Genome Evolution in the Loach Family Botiidae (Order Cypriniformes)

Area of Science:

• Genomics
• Evolutionary Biology
• Comparative Genomics

Background:

• Vertebrates experienced two whole-genome duplications (WGDs), with a third teleost-specific duplication (TSGD or 3R) in ray-finned fishes.
• The order Cypriniformes exhibits further lineage-specific WGDs, contributing to species diversification, but polyploid loaches remain understudied.
• Previous polyploidy research in Cypriniformes has focused on species like carp and goldfish, leaving other taxa like loaches less explored.

Purpose of the Study:

• To provide high-quality, chromosome-level genome assemblies for two understudied loach species: Sinibotia superciliaris and Parabotia fasciatus.
• To reconstruct phylogenetic relationships within Cypriniformes using an integrated comparative genomic framework.
• To introduce and validate a novel, rapid subgenome partitioning method (M3) for analyzing polyploid genomes.

Main Methods:

• Generation of chromosome-level genome assemblies for Sinibotia superciliaris and Parabotia fasciatus.
• Comparative genomic analysis integrating these new genomes with 20 other cypriniform species.
• Development and application of the M3 subgenome partitioning method utilizing differential sequence divergence.

Main Results:

• Phylogenetic relationships within Cypriniformes were reconstructed with enhanced resolution.
• The novel M3 method demonstrated accurate and rapid subgenome partitioning, outperforming existing tools.
• A markedly reduced subgenome was identified in the Golden Chinese Loach, featuring lineage-specific molecular changes in candidate genes.

Conclusions:

• The study provides a comprehensive view of polyploidy and subgenome evolution in loaches, highlighting genomic complexity in Cypriniformes.
• The findings suggest potential adaptive significance for lineage-specific genomic changes in the Golden Chinese Loach.
• The presented genomes and the M3 method offer valuable resources for future research in vertebrate genome evolution and adaptation.