Telomerase RNA evolution: a journey from plant telomeres to broader eukaryotic diversity.

Telomeres, essential for maintaining genomic stability, are typically preserved through the action of telomerase, a ribonucleoprotein complex that synthesizes telomeric DNA. One of its two core components, telomerase RNA (TR), serves as the template for this synthesis, and its evolution across different species is both complex and diverse. This review discusses recent advancements in understanding TR evolution, with a focus on plants (Viridiplantae). Utilizing novel bioinformatic tools and accumulating genomic and transcriptomic data, combined with corresponding experimental validation, researchers have begun to unravel the intricate pathways of TR evolution and telomere maintenance mechanisms. Contrary to previous beliefs, a monophyletic origin of TR has been demonstrated first in land plants and subsequently across the broader phylogenetic megagroup Diaphoretickes. Conversely, the discovery of plant-type TRs in insects challenges assumptions about the monophyletic origin of TRs in animals, suggesting evolutionary innovations coinciding with arthropod divergence. The review also highlights key challenges in TR identification and provides examples of how these have been addressed. Overall, this work underscores the importance of expanding beyond model organisms to comprehend the full complexity of telomerase evolution, with potential applications in agriculture and biotechnology.