Chromosome termini of the monocot plant Othocallis siberica are maintained by telomerase, which specifically synthesises vertebrate‐type telomere sequences

• Published in: The Plant journal : for cell and molecular biology 2004-02, Vol.37 (4), p.484-493
• Main Authors: Weiss‐Schneeweiss, Hanna, Riha, Karel, Jang, Chang Gee, Puizina, Jasna, Scherthan, Harry, Schweizer, Dieter
• Format: Article
• Language: English
• Subjects: Arabidopsis‐type telomeric sequences; Asparagales; Base Sequence; Biological and medical sciences; Brassica - genetics; Chromatin. Chromosome; Chromosome Mapping - methods; Chromosomes, Plant - genetics; Cytogenetic Analysis - methods; DNA Fingerprinting - methods; Endodeoxyribonucleases - metabolism; FISH; Freshwater; Fundamental and applied biological sciences. Psychology; In Situ Hybridization, Fluorescence; Liliaceae - enzymology; Liliaceae - genetics; Liliopsida; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Othocallis siberica; Polymorphism, Restriction Fragment Length; Repetitive Sequences, Nucleic Acid - genetics; telomerase; Telomerase - genetics; Telomerase - metabolism; Telomere - enzymology; Telomere - genetics; TRAP assay; vertebrate‐type telomeric sequences
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313X.2003.01974.x

Lack of Arabidopsis‐type T₃AG₃ telomere sequences has recently been reported for the majority of investigated taxa of the monocot order Asparagales. In order to investigate this phenomenon in more detail, we conducted extensive cytogenetic and molecular analyses of the telomeres in Othocallis siberica, a member of this order. Terminal restriction fragment analysis together with Bal31 exonuclease assay showed that chromosome termini in O. siberica are formed by long stretches (more than 10 kbp) of vertebrate‐type T₂AG₃ repeats. In addition, telomerase activity specifically synthesising (T₂AG₃)n sequence was detected in O. siberica protein extracts by telomerase repeat amplification protocol (TRAP). Fluorescence in situ hybridisation (FISH) revealed the presence of the vertebrate‐type T₂AG₃ telomere sequences at all chromosome termini and at a few additional regions of O. siberica chromosomes, whereas Arabidopsis‐type T₃AG₃ DNA and peptide nucleic acid (PNA) probes did not hybridise to chromosomes of Othocallis, except for polymorphic blocks in chromosomes 2 (interstitial) and 4 (terminal). These interstitial/terminal regions are apparently composed of large blocks of (T₂AG₃)n and (T₃AG₃)n DNA and represent a unique example of interspersion of two types of telomeric repeats within one genome. This may be a reflection of the recent evolutionary switch from Arabidopsis‐ to vertebrate‐type telomeric repeats in this plant group.