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Apoptosis and the selective survival of host animals following thermal bleaching in zooxanthellate corals.

Abstract：

:During the past several decades, numerous reports from disparate geographical areas have documented an increased frequency of "bleaching" in reef-forming corals. The phenomenon, triggered by increased sea surface temperatures, occurs when the cnidarian hosts digest and/or expel their intracellular, photosynthetic dinoflagellate symbionts ("zooxanthellae" in the genus Symbiodinium). Although coral bleaching is often followed by the death of the animal hosts, in some cases, the animal survives and can be repopulated with viable zooxanthellae. The physiological factors determining the ability of the coral to survive bleaching events are poorly understood. In this study, we experimentally established that bleaching and death of the host animal involve a caspase-mediated apoptotic cascade induced by reactive oxygen species produced primarily by the algal symbionts. In addition, we demonstrate that, although some corals naturally suppress caspase activity and significantly reduce caspase concentration under high temperatures as a mechanism to prevent colony death from apoptosis, even sensitive corals can be prevented from dying by application of exogenous inhibitors of caspases. Our results indicate that variability in response to thermal stress in corals is determined by a four-element, combinatorial genetic matrix intrinsic to the specific symbiotic association. Based on our experimental data, we present a working model in which the phenotypic expression of this symbiont/host relationship places a selective pressure on the symbiotic association. The model predicts the survival of the host animals in which the caspase-mediated apoptotic cascade is down-regulated.

journal_name

Proc Natl Acad Sci U S A

journal_title

Proceedings of the National Academy of Sciences of the United States of America

authors

Tchernov D,Kvitt H,Haramaty L,Bibby TS,Gorbunov MY,Rosenfeld H,Falkowski PG

doi

10.1073/pnas.1106924108

subject

Has Abstract

pub_date

2011-06-14 00:00:00

pages

9905-9

issue

eissn

0027-8424

issn

1091-6490

pii

1106924108

journal_volume

108

pub_type

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Apoptosis and the selective survival of host animals following thermal bleaching in zooxanthellate corals.