Dataset Information

Tidal heat pulses on a reef trigger a fine-tuned transcriptional response in corals to maintain homeostasis.

ABSTRACT: For reef-building corals, extreme stress exposure can result in loss of endosymbionts, leaving colonies bleached. However, corals in some habitats are commonly exposed to natural cycles of sub-bleaching stress, often leading to higher stress tolerance. We monitored transcription in the tabletop coral Acropora hyacinthus daily for 17 days over a strong tidal cycle that included extreme temperature spikes, and show that increases in temperature above 30.5°C triggered a strong transcriptional response. The transcriptomic time series data allowed us to identify a set of genes with coordinated expression that were activated only on days with strong tides, high temperature, and large diel pH and oxygen changes. The responsive genes are enriched for gene products essential to the unfolded protein response, an ancient cellular response to endoplasmic reticulum stress. After the temporary heat pulses passed, expression of these genes immediately decreased, suggesting that homeostasis was restored to the endoplasmic reticulum. In a laboratory temperature stress experiment, we found that the expression of these environmentally responsive genes increased as corals bleached, showing that the unfolded protein response becomes more intense during more severe stress. Our results point to the unfolded protein response as a first line of defense that acroporid corals use when coping with environmental stress on the reef, thus enhancing our understanding of coral stress physiology during a time of major concern for reefs.

SUBMITTER: Ruiz-Jones LJ

PROVIDER: S-EPMC5342658 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature

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Tidal heat pulses on a reef trigger a fine-tuned transcriptional response in corals to maintain homeostasis.

Ruiz-Jones Lupita J LJ Palumbi Stephen R SR

Science advances 20170308 3

For reef-building corals, extreme stress exposure can result in loss of endosymbionts, leaving colonies bleached. However, corals in some habitats are commonly exposed to natural cycles of sub-bleaching stress, often leading to higher stress tolerance. We monitored transcription in the tabletop coral <i>Acropora hyacinthus</i> daily for 17 days over a strong tidal cycle that included extreme temperature spikes, and show that increases in temperature above 30.5°C triggered a strong transcriptiona ...[more]

PMID: 28345029

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Project description:In 2016, global temperatures were the highest on record, and mass coral bleaching occurred world-wide. However, around Sesoko Island, Okinawa, southwestern Japan, the heat stress assessed by degree heating week (DHW) based on local temperature measurements was moderate in 2016; in 1998, DHW was three times higher than in 2016 (10.6 vs. 3.3 in September in respective years). On a reef flat of Sesoko Island where the effect of severe coral bleaching on coral assemblage was monitored in 1998, significant coral bleaching occurred in 2016. Bleaching of the heat stress sensitive Acropora corals began in July 2016 on the reef flat as seawater temperature rose. We observed the bleaching and post-bleaching mortality status of individual colonies of Acropora spp. in 2016 in fixed plots on the reef flat. In total, 123 Acropora colonies were followed for six months after seawater temperature became normal by multiple surveys. At the beginning of September 2016, 99.2% of colonies, were either completely (92.7%) or partially (6.5%) bleached. Of those, the dominant species or species groups were A. gemmifera (Ag), A. digitifera (Ad), and tabular Acropora (tA). For all Acropora colonies, the overall whole and partial mortality was 41.5% and 11.4%, respectively. Whole mortality rate differed significantly among species; 72.5%, 17.9%, and 27.8% in Ag, Ad, and tA, respectively. Mortality rates at the end of the surveys were similar in smaller (?10 cm in diameter) and larger Ag, but the former suffered mortality earlier than the latter. Higher survival of smaller colonies was observed only in tA (100%), which may be associated with large morphological differences between smaller and larger colonies. Some of the dominant Acropora colonies had survived without partial mortality including 15.0% survival of the most vulnerable Ag at the end of the surveys. These results suggest that moderate heat stress may have a potential for selecting heat-tolerant genotypes. A longer period of mortality lasting for six months, was observed in Ag in addition to immediate whole mortality after bleaching, due to the continuous loss of living tissue by partial mortality. This highlights the need for multiple surveys at least during several months to accurately assess the impact of thermal stress event to corals. In contrast to DHW based on local measurements, DHW obtained from satellite data were similar between 1998 and 2016. Although satellite-based measurement of sea surface temperature is very useful to reveal variations in heat stress at a large spatial scale, temperature should be measured on site when variations at smaller spatial scales are of interest.

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Dataset Information

Tidal heat pulses on a reef trigger a fine-tuned transcriptional response in corals to maintain homeostasis.

Publications

Tidal heat pulses on a reef trigger a fine-tuned transcriptional response in corals to maintain homeostasis.

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