Molecular characterization of
Chlamydomonas reinhardtii telomeres and telomerase mutants.
Life Sci Alliance 2019;
2:2/3/e201900315. [PMID:
31160377 PMCID:
PMC6549138 DOI:
10.26508/lsa.201900315]
[Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 05/27/2019] [Accepted: 05/27/2019] [Indexed: 12/15/2022] Open
Abstract
This study characterizes the sequence, end structure, and length distribution of Chlamydomonas reinhardtii telomeres and shows that telomerase mutants are defective in telomere maintenance.
Telomeres are repeated sequences found at the end of the linear chromosomes of most eukaryotes and are required for chromosome integrity. Expression of the reverse-transcriptase telomerase allows for extension of telomeric repeats to counteract natural telomere shortening. Although Chlamydomonas reinhardtii, a photosynthetic unicellular green alga, is widely used as a model organism in photosynthesis and flagella research, and for biotechnological applications, the biology of its telomeres has not been investigated in depth. Here, we show that the C. reinhardtii (TTTTAGGG)n telomeric repeats are mostly nondegenerate and that the telomeres form a protective structure, with a subset ending with a 3′ overhang and another subset presenting a blunt end. Although telomere size and length distributions are stable under various standard growth conditions, they vary substantially between 12 genetically close reference strains. Finally, we identify CrTERT, the gene encoding the catalytic subunit of telomerase and show that telomeres shorten progressively in mutants of this gene. Telomerase mutants eventually enter replicative senescence, demonstrating that telomerase is required for long-term maintenance of telomeres in C. reinhardtii.
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