Genomic and Transcriptomic Analysis Reveals Spliced Leader Trans-Splicing in Cryptomonads

Area of Science:

• Molecular Biology
• Eukaryotic Genetics
• Evolutionary Biology

Background:

• Spliced leader trans-splicing (SLTS) is a gene expression mechanism involving a short RNA sequence added to transcripts.
• SLTS is found in diverse eukaryotes and may have evolved multiple times, potentially more frequently in animals.
• Its function in gene regulation or transcriptome diversification is suspected but not fully understood.

Purpose of the Study:

• To investigate the presence and characteristics of SLTS in cryptomonads, a group of unicellular eukaryotes.
• To explore the extent of SLTS and its role in transcriptome diversification within cryptomonads.
• To examine the genomic context of SLTS in cryptomonads, specifically looking for operon structures.

Main Methods:

• Analysis of gene expression in the model cryptomonad Guillardia theta and its relative Hanusia phi.
• Identification and quantification of SLTS events across the transcriptome.
• Comparative genomic analysis to assess operon structures.

Main Results:

• SLTS was identified in at least one-fifth of genes in Guillardia theta and Hanusia phi.
• Hundreds of genes in G. theta produce alternative transcripts via SLTS at alternative sites.
• Little evidence for alternative protein production from alternative SLTS splicing was found.
• No substantial operon structure was detected in the G. theta genome.

Conclusions:

• This study extends the known occurrence of SLTS to cryptomonads, a major group of eukaryotes.
• The findings suggest SLTS is associated with cellular and transcriptomic complexity.
• The precise evolutionary origins and functions of SLTS remain an open area of research.