Major transitions in dinoflagellate evolution unveiled by phylotranscriptomics.

Area of Science:

• Marine Biology
• Evolutionary Biology
• Genomics

Background:

• Dinoflagellates are crucial marine organisms with complex genomes and unresolved evolutionary relationships.
• Understanding their biology is hindered by unique molecular traits and genomic complexity.

Purpose of the Study:

• To infer a robust dinoflagellate phylogeny using a representative transcriptome dataset.
• To map key morphological and molecular evolutionary transitions within dinoflagellates.
• To revise models of thecal tabulation evolution and dinosterol biomarker origins.

Main Methods:

• Phylogenetic inference using a large dinoflagellate transcriptome dataset.
• Integration of molecular, fossil, and biogeochemical data.
• Comparative analysis of metabolic pathways and gene recruitment in dinoflagellates.

Main Results:

• Established the early-branching position of Noctiluca and confirmed monophyly of thecate dinoflagellates.
• Provided evidence for a single origin of the cellulosic theca, linked to cellulase evolution.
• Demonstrated metabolic dependence on plastids in nonphotosynthetic dinoflagellates and proposed mechanisms for eukaryotic plastid dependency.
• Identified three distinct evolutionary waves of DNA-binding protein recruitment in dinoflagellate nuclei.

Conclusions:

• The study provides a robust phylogenetic framework for dinoflagellate evolution.
• Revises understanding of thecal plate evolution and the timing of dinosterol acquisition.
• Highlights the universal metabolic reliance on plastids across free-living dinoflagellates.
• Offers insights into the evolution of nuclear organization and gene acquisition in eukaryotes.