Computational Analysis of Telomerase RNA Evolution in Caenorhabditis Species

Background/Objectives: The telomerase RNA (TR) is an indispensable part of the telomerase protein complex responsible for telomere elongation in most eukaryotic species. Although the telomere terminal repeat sequence (TTAGGC)_n in Caenorhabditis elegans has been known for years, a telomerase RNA gene was not identified in the entire phylum of Nematoda until recently. Methods: In this exploratory study, we employ a combination of different approaches to identify likely telomerase RNA candidates among putative non-coding transcripts. Results: A detailed analysis of our prime candidate shows compelling evidence that it encodes the missing RNA element of the telomerase complex, which is notably located in an intron of the coding gene nmy-2. Using nmy-2 homologs in other nematodes as anchors, we annotate the conserved TR gene in 21 Caenorhabditis species. We furthermore show that the intronic localization of the TR gene is conserved in two distinct branching groups of the Caenorhabditis phylogeny and demonstrate that this property likely emerged from a single point of origin. Conclusions: While the intronic TR represents a very interesting evolutionary adaption that seems to have been successful in the Elegans and Japonica groups, the question regarding the macroscopic nematode TR evolution remains.