From cryptogene to gene? ND8 editing domain reduction in insect trypanosomatids

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Parasitology

Background:

• The mitochondrial ND8 gene in trypanosomatids undergoes RNA editing, primarily pan-editing or 5'-editing.
• Previous studies indicated that ND8 cryptogenes often lack complete open reading frames (ORFs) and start codons.

Purpose of the Study:

• To investigate the ND8 gene sequence and RNA editing patterns in three insect trypanosomatid species.
• To compare novel sequences with known ND8 cryptogenes and mature mRNAs from other trypanosomatids.
• To elucidate the evolutionary history of ND8 cryptogene structure.

Main Methods:

• Sequencing of ND8 nucleotide from "Wallaceina" sp. Wsd, Leptomonas rigidus, and Leptomonas collosoma.
• Comparative analysis of obtained sequences with existing trypanosomatid ND8 data.
• Phylogenetic analysis using 18S rRNA sequences.

Main Results:

• A new RNA editing pattern was identified, characterized by 18 U insertions in the 5' region of the primary transcript.
• The potential start codon is encoded at the DNA level, resulting in a putative ORF in the pre-edited ND8 sequence.
• Phylogenetic analysis grouped species based on their ND8 gene editing patterns (encoded ORF, 5'-edited, pan-edited).

Conclusions:

• This study presents the first instance of a pre-edited ND8 sequence containing a complete putative ORF and start codon.
• The findings suggest that the evolution of cryptogene structure involved multiple reductions in editing domain length.
• The observed grouping in phylogenetic analysis supports the evolutionary divergence of ND8 editing mechanisms.