Transposable elements in fish chromosomes: a study in the marine cobia species

Area of Science:

• Genomics
• Molecular Biology
• Marine Biology

Background:

• Rachycentron canadum is of biotechnological interest for aquaculture.
• Understanding repetitive DNA sequences is crucial for genome evolution.
• Previous research focused on gene location in R. canadum chromosomes.

Purpose of the Study:

• To physically map transposable elements (TEs) and rRNA genes in R. canadum chromosomes.
• To investigate the distribution and colocalization patterns of these repetitive sequences.
• To understand the implications for genome organization and evolution.

Main Methods:

• Fluorescence in situ hybridization (FISH) was used for physical mapping.
• Mapping targeted the Tol2 transposable element, Rex1 and Rex3 retrotransposons, and 18S and 5S rRNA genes.
• Analysis focused on distribution within euchromatic and heterochromatic regions.

Main Results:

• The Tol2 TE is homogeneously distributed in euchromatic regions, often colocalizing with 18S rDNA.
• Rex1 elements preferentially associate with heterochromatic regions.
• Rex3 elements show scarce distribution in euchromatic regions, with varied dispersion patterns.
• Colocalization of TEs with rDNA sites indicates complex repetitive sequence regions.

Conclusions:

• R. canadum exhibits a distinct chromosomal organization of TEs and rRNA genes.
• Heterogeneous colonization of TEs may influence evolutionary rates of heterochromatic regions.
• These findings contribute to understanding genome evolution in marine fish.