Telomeres and Telomerase Activity in Scleractinian Corals and Symbiodinium spp.

Abstract

Telomeres are the repetitive sequences of DNA and associated proteins that cap the ends of eukaryotic chromosomes and play an essential role in maintaining chromosome stability. Compromised telomeres can lead to cell cycle arrest, senescence, apoptosis, or genetic instability, whereas maintenance of telomeres can endow cells with the capacity for indefinite self-renewal. Telomere integrity is maintained in most cells by the activity of telomerase, a ribonucleoprotein that can catalyze the addition of repeat sequences onto chromosome ends. Using the telomeric repeat amplification protocol (TRAP) assay, we detected telomerase activity in host nuclear extracts prepared from two scleractinian corals, Madracis auretenra and Madracis decactis, and also in cultured Symbiodinium, the symbiotic algae that live within corals. Sequencing the TRAP reaction products indicated that the telomeric DNA repeat sequence was TTAGGG for coral and TTTAGGG for Symbiodinium. Using this sequence information, we estimated telomere lengths by terminal restriction fragment (TRF) analysis to be greater than 19 kb for several species of coral and their associated Symbiodinium. Maintenance of coral telomeres by telomerase activity may be a mechanism that confers continuous growth and reproductive plasticity to these long-lived organisms.

Somatic tissues of the coral <i>Galaxea fascicularis</i> possess telomerase activity

“…fascicularis possess telomerase activity, and is consistent with recent report that telomerase was detected in nuclear extract of three coral species (Zielke and Bodnar 2010).…”

“…The result proves that telomeres of the coral G. fascicularis contained TTAGGG repeats. This is consistent with recent studies that the telomere sequence is highly conserved among basal metazoans (Traut et al 2007), and that the telomeres of some corals possess the TTAGGG motif (Sinclair et al 2006;Zielke and Bodnar 2010).…”

Do reef corals age?

“…Several preliminary studies describe telomere characteristics in corals (Sinclair, Richmond & Ostrander, 2007;Zielke & Bodnar, 2010;Nakamichi et al, 2012) (Table 2). For the short-lived branching coral Acropora digitifera telomere length was significantly longer in sperm than in the planulae which was in turn longer than in adult polyps (Tsuta et al, 2014).…”

Karyotyping and single-gene detection using fluorescence in situ hybridization on chromosomes of Hydra magnipapillata (Cnidaria: Hydrozoa)

“…have uncovered telomerase activity in somatic tissues of both the polyp and medusa stages (Ojimi et al, 2009). In several species of coral telomere lengths were greater than 19 kb (Zielke, Bodnar, 2010).…”