Differential nitric oxide synthesis and host apoptotic events correlate with bleaching susceptibility in reef corals

Hawkins, T. D., Kueger, T., Becker, S., Fisher, P. L. and Davy, S. K. (2014) Differential nitric oxide synthesis and host apoptotic events correlate with bleaching susceptibility in reef corals. Coral Reefs, 33 1: 141-153. doi:10.1007/S00338-013-1103-4

Author Hawkins, T. D.
Kueger, T.
Becker, S.
Fisher, P. L.
Davy, S. K.
Title Differential nitric oxide synthesis and host apoptotic events correlate with bleaching susceptibility in reef corals
Journal name Coral Reefs   Check publisher's open access policy
ISSN 0722-4028
Publication date 2014-02-04
Sub-type Article (original research)
DOI 10.1007/S00338-013-1103-4
Open Access Status
Volume 33
Issue 1
Start page 141
End page 153
Total pages 13
Place of publication Heidelberg, Germany
Publisher Springer
Collection year 2015
Language eng
Formatted abstract
Coral bleaching poses a threat to coral reefs worldwide. As a consequence of the temperature-induced breakdown in coral-dinoflagellate symbiosis, bleaching can have extensive effects on reef communities. However, our understanding of bleaching at a cellular level is limited, and this is particularly true regarding differential susceptibility among coral species. Recent work suggests that bleaching may represent a host innate immune-like response to symbiont dysfunction that involves synthesis of the signalling compound nitric oxide (NO) and the induction of host apoptotic-like cell death. In this study, we examined the activity of apoptosis-regulating enzymes alongside oxidised NO accumulation (a proxy for NO synthesis) in the reef corals Acropora millepora, Montipora digitata, and Pocillopora damicornis during experimental thermal stress. P. damicornis was the most sensitive species, suffering mortality (tissue sloughing) after 5 days at 33 °C but non-lethal bleaching after 9 days at 31.5 °C. A. millepora bleached at 33 °C but remained structurally intact, while M. digitata showed little evidence of bleaching. P. damicornis and A. millepora both exhibited evidence of temperature-induced NO synthesis and, after 5 days of heating, levels of oxidised NO in both species were fivefold higher than in controls maintained at 28.5 °C. These responses preceded bleaching by a number of days and may have occurred before symbiont dysfunction (measured as chlorophyll a degradation and oxidised NO accumulation). In A. millepora, apparent NO synthesis correlated with the induction of host apoptotic-like pathways, while in P. damicornis, the upregulation of apoptotic pathways occurred later. No evidence of elevated NO production or apoptosis was observed in M. digitata at 33 °C and baseline activity of apoptosis-regulating enzymes was negligible in this species. These findings provide important physiological data in the context of the responses of corals to global change and suggest that early events in the host may be important in the collapse of the coral-dinoflagellate symbiosis.
Keyword Thermal stress
Climate change
Cnidarian–dinoflagellate symbiosis
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Civil Engineering Publications
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Citation counts: TR Web of Science Citation Count  Cited 7 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 8 times in Scopus Article | Citations
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Created: Thu, 06 Nov 2014, 12:40:48 EST by Paul Fisher on behalf of School of Civil Engineering