Abstract

Key message tRNA Adenosine Deaminase 3 helps to sustain telomere tracts in a telomerase-independent fashion, likely through regulating cellular metabolism. Telomere length maintenance is influenced by a complex web of chromatin and metabolism-related factors. We previously reported that a lncRNA termedAtTER2regulates telomerase activity inArabidopsis thalianain response to DNA damage.AtTER2was initially shown to partially overlap with the 5 ' UTR of thetRNA ADENOSINE DEAMINASE 3(TAD3) gene. However, updated genome annotation showed thatAtTER2was completely embedded inTAD3, raising the possibility that phenotypes ascribed toAtTER2could be derived fromTAD3. Here we show through strand-specific RNA-Seq, strand-specific qRT-PCR and bioinformatic analyses thatAtTER2does not encode a stable lncRNA. Further examination of the originaltad3(ter2-1/tad3-1) mutant revealed expression of an antisense transcript driven by a cryptic promoter in the T-DNA. Hence, a new hypomorphic allele ofTAD3(tad3-2) was examined.tad3-2mutants showed hypersensitivity to DNA damage, but no deregulation of telomerase, suggesting that the telomerase phenotype oftad3-1mutants reflects an off-target effect. Unexpectedly, however,tad3-2plants displayed progressive loss of telomeric DNA over successive generations that was not accompanied by alteration of terminal architecture or end protection. The phenotype was exacerbated in plants lacking the telomerase processivity factorPOT1a, indicating thatTAD3promotes telomere maintenance through a non-canonical, telomerase-independent pathway. The transcriptome oftad3-2mutants revealed significant dysregulation of genes involved in auxin signaling and glucosinolate biosynthesis, pathways that intersect the stress response, cell cycle regulation and DNA metabolism. These findings indicate that theTAD3locus indirectly contributes to telomere length homeostasis by altering the metabolic profile inArabidopsis.