Contrasting modes of intron evolution in an evolutionarily distinct eukaryotic lineage revealed by comparative genomics of ciliated protists.

Deep-branching ciliates experienced massive intron loss and predominantly retain tiny 3n introns, revealing contrasting intron evolution modes in unicellular eukaryotes.

• Why it matters: Understanding intron evolution in ancient unicellular eukaryotes fills a critical gap in genome biology, as their patterns differ from well-studied multicellular organisms, impacting gene regulation insights.
• What they did: Using a newly sequenced high-quality genome and comparative genomics across ciliate lineages, the study analyzed intron patterns, spliceosome components, and whole-genome duplications, focusing on 27,571 genes in Blepharisma.
• The result: Findings show deep-branching ciliates underwent extensive intron loss and retained small introns likely to facilitate mRNA decay, providing new perspectives on unconventional intron evolution and regulation strategies.