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Spliced-leader trans-splicing in freshwater planarians
Ricardo M Zayas1, Tyler D Bold, Phillip A Newmark
1Department of Cell and Developmental Biology, University of Illinois at Urbana, Champaign, USA.
Molecular Biology and Evolution
|June 24, 2005
Summary
Trans-splicing, a gene expression mechanism, was identified in the freshwater planarian Schmidtea mediterranea. This finding supports trans-splicing as an ancestral trait in Platyhelminthes, offering a new model for studying this RNA processing.
Area of Science:
- Molecular Biology
- Genetics
- Eukaryotic Gene Expression
Background:
- Trans-splicing, a post-transcriptional RNA processing event, involves appending a spliced-leader (SL) RNA to pre-mRNAs.
- This mechanism is observed across diverse eukaryotes, including protozoans and chordates.
- Previous studies have documented trans-splicing in various Platyhelminthes classes like trematodes, cestodes, and polyclads.
Purpose of the Study:
- To investigate the presence and characteristics of trans-splicing in the freshwater planarian Schmidtea mediterranea.
- To determine if trans-splicing is an ancestral feature within the Platyhelminthes phylum.
Main Methods:
- Analysis of expressed sequence tag (EST) collections from Schmidtea mediterranea.
- Genomic sequence analysis of transcripts exhibiting shared 5' sequences.
- RNA blot analysis and 5'/3' rapid amplification of cDNA ends (RACE).
Main Results:
- Over 300 Schmidtea mediterranea transcripts were found to share one of two distinct spliced-leader sequences (Smed SL-1 and SL-2) at their 5' ends.
- These SL sequences (42-nt) were derived from distinct small RNAs (approx. 110 nt) transcribed elsewhere in the genome.
- Homologous SL sequences were also detected in the planarian Dugesia japonica, supporting broader occurrence within Platyhelminthes.
Conclusions:
- The identification of trans-splicing in two triclad planarians (Schmidtea mediterranea and Dugesia japonica) strengthens the hypothesis that it is an ancestral RNA processing mode in Platyhelminthes.
- Schmidtea mediterranea presents a valuable model system for future research into the functional roles of trans-splicing due to its experimental tractability and genomic resources.