Parallel Evolution of Transcription Factors in Basal Metazoans

Area of Science:

• Evolutionary developmental biology
• Genomics
• Animal evolution

Background:

• Transcription factors (TFs) regulate gene expression and are essential for animal development.
• Understanding TF evolution in basal metazoans like ctenophores is key to deciphering early animal body plan origins.
• Previous studies lacked comprehensive TF catalogs for ctenophores, hindering comparative analyses.

Purpose of the Study:

• To create a comprehensive catalog of transcription factors in two ctenophore species.
• To compare TF repertoires across diverse metazoans to understand body plan evolution.
• To investigate the role of TF diversification in the emergence of ctenophore complexity.

Main Methods:

• Genome-wide identification and cataloging of transcription factors in Pleurobrachia bachei and Mnemiopsis leidyi.
• Comparative genomic analysis of TF repertoires across selected metazoan phyla.
• Phylogenetic analysis to identify lineage-specific TF expansions and potential novel TF origins.

Main Results:

• Identified 428 TFs in Pleurobrachia bachei and 418 TFs in Mnemiopsis leidyi.
• Ctenophores possess a larger TF repertoire compared to simpler metazoans like sponges (Amphimedon, 277 TFs) and placozoans (Trichoplax, 274 TFs).
• Significant lineage-specific expansions were observed in zinc finger C2H2 (ZF-C2H2) and homeobox TF superfamilies in ctenophores, and leucine zipper (BZIP) TFs in sponge and placozoan lineages.
• Evidence suggests mobile element domestication contributed to lineage-specific TF evolution.

Conclusions:

• Ctenophores exhibit a highly diverse set of transcription factors, correlating with their complex body plan.
• TF evolution, including lineage-specific expansions and potential novel origins via mobile elements, played a significant role in metazoan body plan diversification.
• Comparative genomics of TFs provides insights into the evolutionary mechanisms underlying animal complexity.