title: 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 coralAcropora hyacinthusdaily 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.
authors.affiliation: Department of Biology, Hopkins Marine Station, Stanford University, 120 Ocean View Boulevard, Pacific Grove, CA 93950, USA.
authors.forename: Lupita J
authors.initials: LJ
authors.lastname: Ruiz-Jones
authors.affiliation: Department of Biology, Hopkins Marine Station, Stanford University, 120 Ocean View Boulevard, Pacific Grove, CA 93950, USA.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Palumbi
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000378:metabolism*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D010100:Oxygen / Q000378:metabolism; D013312:Stress, Physiological; D014158:Transcription, Genetic; D056811:Unfolded Protein Response
chemical_list: D010100:Oxygen
keywords: coral; coral bleaching; coral reef; ecological physiology; endoplasmic reticulum stress; environmental variability; transcriptomics; unfolded protein response