To elucidate the molecular nature of evolutionary changes of telomeres in the plant order Asparagales, we aimed to characterize telomerase RNA subunits (TRs) in these plants. The unusually long telomere repeat unit in Allium plants (12 nt) allowed us to identify TRs in transcriptomic data of representative species of the Allium genus. Orthologous TRs were then identified in Asparagales plants harbouring telomere DNA composed of TTAGGG (human type) or TTTAGGG (Arabidopsis-type) repeats. Further, we identified TRs across the land plant phylogeny, including common model plants, crop plants, and plants with unusual telomeres. Several lines of functional testing demonstrate the templating telomerase function of the identified TRs and disprove a functionality of the only previously reported plant telomerase RNA in Arabidopsis thaliana. Importantly, our results change the existing paradigm in plant telomere biology which has been based on the existence of a relatively conserved telomerase reverse transcriptase subunit (TERT) associating with highly divergent TRs even between closely related plant taxa. The finding of a monophyletic origin of genuine TRs across land plants opens the possibility to identify TRs directly in transcriptomic or genomic data and/or predict telomere sequences synthesized according to the respective TR template region.

Rationale: Cardioprotective pathways may involve a mitochondrial ATP-sensitive potassium (mitoK ATP ) channel but its composition is not fully understood. Objective: We hypothesized that the mitoK ATP channel contains a sulfonylurea receptor (SUR)2 regulatory subunit and aimed to identify the molecular structure. Methods and Results: Western blot analysis in cardiac mitochondria detected a 55-kDa mitochondrial SUR2 (mitoSUR2) short form, 2 additional short forms (28 and 68 kDa), and a 130-kDa long form. RACE (Rapid Amplification of cDNA Ends) identified a 1.5-Kb transcript, which was generated by a nonconventional intraexonic splicing ( Key Words: K ATP channel Ⅲ SUR2 Ⅲ ischemia Ⅲ intraexonic splicing Ⅲ mitochondria A lternative splicing generates multiple mRNAs from a single gene, which are subsequently translated into diverse proteins with different structures and functions. 1 Up to 60% of mammalian genes are alternatively spliced. 2 Eukaryotic ion channel genes are known to have multiple splice variants. The ATP-sensitive potassium (K ATP ) channels are ubiquitously distributed in many tissue types. Sarcolemmal K ATP (sarcK ATP ) channels consist of a potassium inward-rectifier pore-forming subunit (Kir6.0) and a sulfonylurea receptor (SUR) regulatory subunit. 3 Various isoforms and splice variants for the SUR genes have been reported. 4,5 The cardiac muscle splice variant (SUR2A) differs from the vascular smooth muscle splice variant (SUR2B) in the alternative use of the SUR2 C-terminal exon. 6,7 Subtypes of splice variants for SUR2A or SUR2B that lack exon 14 or exon 17 exist in mice 7,8 and humans. 9 Moreover, sarcolemmal SUR short variants are found in heart 10 and pancreatic ␤ cells. 11,12 The copresence of multiple splice variants increases the functional diversity and genetic complexity of K ATP channels.In addition to a sarcolemmal location, 13 the K ATP channel is present in the inner membrane of mitochondria (mitoK ATP ). 14 Both forms of channels are involved in cardioprotective pathways, 15 but earlier pharmacological evidence suggests that the mitoK ATP channel is more critical in conferring protection. 16,17 However, the molecular composition of the mitoK ATP channel is uncertain, hampering present efforts in elucidating its role in preconditioning signaling. 18 Putative mitoK ATP channel subunits in the sizes of 55 and 63

In the current meiotic recombination initiation model, the SPO11 catalytic subunits associate with MTOPVIB to form a Topoisomerase VI-like complex that generates DNA double strand breaks (DSBs). Four additional proteins, PRD1/AtMEI1, PRD2/AtMEI4, PRD3/AtMER2 and the plant specific DFO are required for meiotic DSB formation. Here we show that (i) MTOPVIB and PRD1 provide the link between the catalytic sub-complex and the other DSB proteins, (ii) PRD3/AtMER2, while localized to the axis, does not assemble a canonical pre-DSB complex but establishes a direct link between the DSB-forming and resection machineries, (iii) DFO controls MTOPVIB foci formation and is part of a divergent RMM-like complex including PHS1/AtREC114 and PRD2/AtMEI4 but not PRD3/AtMER2, (iv) PHS1/AtREC114 is absolutely unnecessary for DSB formation despite having a conserved position within the DSB protein network and (v) MTOPVIB and PRD2/AtMEI4 interact directly with chromosome axis proteins to anchor the meiotic DSB machinery to the axis.