The transcriptomic response to thermal stress is immediate, transient and potentiated by ultraviolet radiation in the sea anemone Anemonia viridis

Abstract

Among the environmental threats to coral reef health, temperature and ultraviolet increases have been proposed as major agents, although the relative contribution of each in the cnidarian/zooxanthellae symbiosis breakdown has been poorly addressed. We have investigated the transcriptomic response to thermal stress, with and without ultraviolet radiation (UVR), in the symbiotic sea anemone Anemonia viridis. Using the Oligo2K A. viridis microarray, dedicated to genes potentially involved in the symbiosis interaction, we monitored the gene expression profiles after 1, 2 and 5 days of stresses that further lead to massive losses of zooxanthellae. Each stress showed a specific gene expression profile with very little overlap. We showed that the major response to thermal stress is immediate (24 h) but returns to the baseline gene expression profile after 2 days. UVR alone has little effect but potentiates thermal stress, as a second response at 5 days was observed when the two stresses were coupled. Several pathways were highlighted, such as mesoglea loosening, cell death and calcium homeostasis and described in more details. Finally, we showed that the dermatopontin gene family, potentially involved in collagen fibrillogenesis, issued from actinarian-specific duplication events, with one member preferentially expressed in the gastroderm and specifically responding to stress. Anemonia viridis EST sequences have been deposited into GenBank dbEST ([GenBank:FK719875–FK759813].

Gene Expression Dynamics Accompanying the Sponge Thermal Stress Response

“…tubifera resulted in more downregulation than upregulation of genes (Table A in S1 File). This finding is consistent with transcriptome-wide studies in other organisms, suggesting that widespread downregulation is a conserved phenomenon under stressful conditions [24–26]. This may be an adaptive mechanism that reflects the redirection of energy and resources towards the maintenance and repair of cellular machinery.…”

Host and Symbionts in Pocillopora damicornis Larvae Display Different Transcriptomic Responses to Ocean Acidification and Warming

“…In contrast to previous studies on the animal compartment of other species (Voolstra et al, 2009;Moya et al, 2015), here there was no evidence that exposure to either increased temperature or increased pCO 2 led to upregulation of a generalized cellular stress response in P. damicornis larvae. We also observed no transcriptomic evidence for either depressed metabolism (as in Voolstra et al, 2009;Moya et al, 2012) or elevated metabolism (as in Davies et al, 2016) in response to high pCO 2 . These results support the above hypothesis that the coral larvae can tolerate high temperature and high pCO 2 using mechanisms other than changes in gene expression.…”

Carbonic anhydrase activity changes in response to increased temperature and pCO2 in Symbiodinium–zoanthid associations

“…Alternatively, reduction in algal CA activity at higher temperature could point to a greater flux of "recycled" CO 2 from increased host respiration at the higher temperatures. In symbiotic cnidarians, high pCO 2 has been shown to both up-regulate and down-regulate CA gene expression in corals (see Bertucci et al, 2013;Moya et al, 2012b). This may point to speciesspecific differences in CA efficiencies, and/or different mechanisms of DIC uptake and transport.…”