Linear chromosomes offer many advantages over circular DNA for transcription and replication of large genomes, hence their prevalence in eukaryotes. But the linear arrangement of the DNA has a massive Achilles heel: the terminal ends, or telomeres, are unstable and prone to mutation. Moreover, DNA replication cannot proceed to the end of a linear DNA molecule because the synthesis of Okazaki fragments needs RNA primers to bind ahead of the lagging strand. Eukaryotes deal with both of these problems by adding repetitive DNA sequences to the telomeres that act as a disposable buffer, protecting terminal genes from being truncated during replication and from mutation. Because the telomere is shortened during each DNA replication, it is necessary to resynthesise telomere DNA using an enzyme, telomerase reverse transcriptase. Our understanding of telomere biology is dominated by research into human telomeres. This is understandable due to the links between telomere biology and cellular mortality, ageing and a range of diseases including cancer. However, telomere biology in plants shows some specific differences to humans which may be crucial in our understanding of telomere biology in general. For example, telomerase activity in plant cells is well balanced with the cellular proliferation rate. The reversible regulation of telomerase activity is thought to be important in this context: its activity is turned off in differentiated tissues and turned on during cell periods of active cell replication, for example, during regeneration of plant tissues. Understanding the mechanism for this reversible regulation of telomerase activity could be beneficial in biomedical applications of telomere biology in humans. But where to start? From protozoans and humans, it was known that telomerase was a ribonucleoprotein, carrying its own RNA molecules that are complementary to the telomere repeats and are used as a template for telomere elongation, catalysed by the reverse transcriptase activity of the enzyme. But, in addition, a number of accessory proteins are required to deliver functional telomerase to the telomeres, to regulate its activity and to protect the elongated telomere from DNA repair enzymes. These components assemble into two distinct complexes known as shelterin and CST. Functional homologues of the CST complex have been identified in plants, but the same is not true for the shelterin complex. In plants, not all of the homologues of the six core shelterin components exist, and only some of them seem to be associated with telomeres in vivo. The goal, therefore was to identify undiscovered telomerase accessory proteins in plants and to establish how active telomerase is formed and regulated. Jiří Fajkus and his research group at Masaryk University, have been working on plant telomeres for over 20 years. A key member of his team in the hunt for plant telomerase-associated proteins has been Petra Procházková Schrumpfová, first as a Ph.D. student and then through several postdoc periods. Working in Arabidopsis, the group had already established that Telomere Repeat Binding proteins (TRB) were involved in recruitment of telomerase to the telomeres. These proteins are specific to plants and contain an N–terminal Myb-like domain which is responsible for specific recognition of telomeric DNA. Attention turned to the plant homologues of two human telomere associated proteins called Pontin and Reptin after they turned up in a pull-down of TERT, the catalytic subunit of Arabidopsis telomerase, in an experiment done in collaboration with Eva Sýkorová's group at the Institute of Biophysics in Brno. The plant Pontin and Reptin homologues are encoded by RuvBL1 and RuvBL2a, respectively. But despite the fact that RuvBL proteins were isolated from plant cells as TERT-associated, Jiří and his team were not able to prove a direct interaction between TERT and RuvBL as had already been described in mammals. Serendipity then intervened. During their characterisation of RuvBL interactions with TERT, they used several proteins as negative controls. Surprisingly, one of the supposed negative controls showed reproducibly positive interaction with RuvBL proteins. It was in this way that they discovered that TRB proteins interact with RuvBL. Knowing that TRB proteins directly interact with TERT they started to closely characterise the trimeric complex TERT-TRB-RuvBL and that is the focus of the highlighted paper which is drawn from the MSc and PhD research of Šárka Schořová with Petra Procházková Schrumpfová and Jiří Fajkus as joint corresponding authors. The work also involved Lenka Záveská Drábková, a postdoc from David Honys's group at the Institute of Experimental Botany in Prague who did phylogenetic analysis of the RuvBL family in plants. That collaboration started late one afternoon during a short-term visit of Petra Procházková Schrumpfová to David Honys's lab that was focused on a completely different scientific topic. Such is the nature of science and scientists! In this highlighted paper (Schořová et al., 2019), a combination of BiFC, yeast-two hybrid and pull-down assays confirmed that there is no direct interaction between RuvBLs and TERT, but that the interaction is mediated by TRBs as an intermediary. It was also shown that RuvBL proteins form hetero- and homo-oligomers in vivo. Proof of the importance of RuvBL1/2 for telomerase biogenesis was provided by analysis of Arabidopsis knockout lines which had substantially reduced telomerase activity in flower buds (a rapidly proliferating tissue with high telomerase requirement). This crucial experiment turned out to be the hardest part of the research, with identification of knockout alleles a real struggle. Jiří and Petra say that they had to genotype hundreds of individual plants from several lines and were only able to identify a few heterozygous individuals of each gene with homozygous mutants being lethal. Further protein interaction experiments identified another protein in the complex: CBF5, a homologue of mammalian dyskerin, a known telomerase-associated protein. Cell biological analyses were able to place all of these proteins in the nucleolus and some of them in Cajal bodies and, combined with previous studies, the authors were able to put together the most complete picture of the plant telomerase complex to date, as shown in Figure 1. RuvBL1 and RuvBL2a, are orthologues of human Pontin and Reptin, respectively, in Arabidopsis. Besides their mutual interactions, RuvBL1 associates with the catalytic subunit of telomerase (TERT) in the nucleolus in vivo. In contrast to mammals, interactions between TERT and RuvBL proteins in Arabidopsis are not direct but are mediated by one of the Telomere Repeat Binding (TRB) proteins. The plant orthologue of human dyskerin, named CBF5, is indirectly associated with TRB proteins but not with the RuvBL proteins in the plant nucleus/nucleolus, and interacts with the Protection of telomere 1 (POT1a) in the nucleolus or cytoplasmic foci. One of the most interesting facets of this picture is the similarities and divergence between plants and humans. On the one hand, identification of Reptin and Pontin in Arabidopsis and their conservation in humans, shows that the factors involved in telomerase biogenesis and function are evolutionary ancient. On the other, the interactions and mechanism of action of plant Reptin and Pontin is different than in human cells. The TERT subunit of Arabidopsis telomerase does not interact directly with Reptin and Pontin but through TRBs which in human cells are telomere-associated proteins but not TERT-accessory factors. This reveals that different mechanisms have evolved although using basically the same set of factors, a finding that would justify a similar study in other eukaryotic lineages to define the evolutionary history of complex formation between telomeric repeats, TERT, accessory factors and shelterin proteins. One possible reason to explain the variety of mechanisms suggested by this study is the specific organization, and possibly the 3D structure, of TERT RNA (TER) molecules which may limit the ability of TERT to interact directly with them or require other bridging proteins, as it occurs in Arabidopsis. Differences in the subnuclear localization of telomeric sequences may be also important. For Jiří and his team, work will continue to unpick the regulation of synthesis of both basic subunits of telomerase, TER and TERT, their intracellular trafficking and assembly into the holoenzyme complex, together with a number of associated factors.