Genome sizes and repeatome evolution in zoantharians (Cnidaria: Hexacorallia: Zoantharia)

Area of Science:

• Genomics
• Evolutionary Biology
• Marine Biology

Background:

• Genome size varies significantly across eukaryotes, even in related species, a phenomenon partly attributed to transposable elements.
• The evolutionary implications of genome size variation and transposable element dynamics remain poorly understood, contributing to the 'C-value enigma'.
• Zoantharia, ecologically important benthic cnidarians, are understudied genomically.

Purpose of the Study:

• To investigate the role of the repeatome in genome size variation across the order Zoantharia.
• To analyze the abundance and types of repeated DNA elements in zoantharian genomes.
• To understand the evolutionary forces shaping genome size in these marine invertebrates.

Main Methods:

• Whole-genome sequencing of 32 zoantharian species from five families.
• Estimation of genome sizes and quantification of different repeat classes.
• Sequence clustering to assess repeat overlap and identify species-specific amplification patterns.

Main Results:

• Zoantharian genome sizes varied up to 2.4-fold.
• Significant correlations were found between genome size and both total repeated DNA content and transposable element abundance.
• Long interspersed nuclear elements and DNA transposons were the most abundant transposable elements, showing recent expansion, while satellite elements showed species-specific amplification.

Conclusions:

• Zoantharian genome sizes are shaped by complex dynamics of various repeated elements.
• Transposable elements play a significant role in genome size expansion and reduction in this order.
• A substantial portion of repeated elements remain unannotated, underscoring the need for further research into non-model cnidarian genomes and their evolutionary impact.