RNA Tailing by Nucleotidyltransferases in Plants: Mechanisms, Functions, and Biological Significance

RNA tailing, the non-templated addition of nucleotides to RNA 3' ends, is a conserved post-transcriptional modification that plays a critical role in regulating RNA metabolism. In plants, this process is primarily mediated by nucleotidyltransferase proteins (NTPs). In this review, we analyze current knowledge of plant NTPs by integrating evidence from genetic, biochemical, and phylogenetic analyses of the gene-family across model plants and crops. We summarize the composition and evolutionary diversification of the plant NTP gene family, with emphasis on lineage-specific expansion and conservation patterns. Using <i>Arabidopsis thaliana</i> as a reference framework, we then describe the molecular roles of NTPs in the tailing of distinct RNA classes, emphasizing how tail type and length confer context-dependent regulatory outcomes including stabilization versus degradation and processing/maturation versus clearance. We further examine the determinants of substrate choice, focusing on RNA type, terminal structure, and subcellular localization. Finally, we discuss the biological functions of NTP-mediated RNA tailing in plants, linking RNA tailing to development, stress responses, antiviral immunity, and agronomic traits in crops. We conclude by outlining key mechanistic and physiological challenges that define future directions for understanding and harnessing NTP-mediated RNA regulation. Collectively, this review provides an integrated framework for understanding how RNA tailing by NTPs shapes plant RNA metabolism and biological fitness.