DNA barcoding in autotrophic euglenids: evaluation of COI and 18s rDNA

Area of Science:

• Microbial Eukaryotic Ecology
• Molecular Systematics
• Phycology

Background:

• Autotrophic euglenids (Euglenophyceae) are abundant freshwater microbial eukaryotes.
• Species identification using light microscopy is challenging due to limited observable features.
• Molecular identification requires reliable DNA barcodes for accurate taxonomic classification.

Purpose of the Study:

• To identify and validate suitable DNA barcode markers for autotrophic euglenids.
• To assess the efficacy of COI and 18S rDNA markers for molecular identification.
• To establish a standardized molecular approach for euglenid taxonomy.

Main Methods:

• Literature review to select verified species and available molecular markers.
• Analysis of the cytochrome c oxidase subunit I (COI) gene using 43 sequences from 24 species.
• Evaluation of the 18S ribosomal DNA (rDNA) marker, including the whole sequence and three variable regions (V1V2, V2V3, V4), using 263 sequences from 86 species.

Main Results:

• The COI gene was unsuitable as a DNA barcode due to a lack of universal primer sites.
• The whole 18S rDNA sequence was too long for practical barcode applications.
• Variable regions V2V3 and V4 of 18S rDNA demonstrated high efficiency (above 95% and 90%, respectively) as potential DNA barcodes.

Conclusions:

• Variable regions V2V3 and V4 of 18S rDNA are recommended as effective DNA barcodes for autotrophic euglenids.
• These markers facilitate accurate molecular identification and taxonomic studies of Euglenophyceae.
• The findings provide a foundation for future molecular research on freshwater microbial eukaryotes.