Transcriptomic Resilience of the Montipora digitata Holobiont to Low pH

Abstract

Ocean acidification is considered as one of the major threats for coral reefs at a global scale. Marine calcifying organisms, including stony corals, are expected to be the most affected by the predicted decrease of the surface water pH at the end of the century. The severity of the impacts on coral reefs remains as a matter of controversy. Although previous studies have explored the physiological response of stony corals to changes in pH, the response of the holobiont (i.e., the coral itself plus its symbionts) remains largely unexplored. In the present study, we assessed the changes in overall gene expression of the coral Montipora digitata and its microalgal symbionts after a short (3 days) and a longer (42 days) exposure to low pH (7.6). The short-term exposure to low pH caused small differences in the expression level of the host, impacting mostly genes associated with stress response in other scleractinians. Longer exposure to low pH resulted in no significant changes in gene expression of treated vs. control coral hosts. Gene expression in the eukaryotic symbionts remained unaltered at both exposure times. Our findings suggest resilience, in terms of gene expression, of the M. digitata holobiont to pH decrease, as well as capability to acclimatize to extended periods of exposure to low pH.

Regulation of ion transport and energy metabolism enables certain coral genotypes to maintain calcification under experimental ocean acidification

“…Downregulation of transcription‐related genes has been observed in shallow‐water corals in response to thermal stress and may be a prolonged stress response to both temperature and OA (Kaniewska et al., 2015; Polato, Altman, & Baums, 2013; Portune, Voolstra, Medina, & Szmant, 2010). Genes associated with apoptosis and immune response including tumor necrosis factor receptor family members, heat shock proteins (Barshis et al., 2013; Moya et al., 2015), zinc‐metalloproteases (Barshis et al, 2013; González‐Pech, Vargas, Francis, & Wörheide, 2017), and Bcl‐2 members (Moya et al., 2015) are frequently involved in general coral stress responses, including low pH. No transcripts annotated as Bcl‐2, only one as TNFR, and 2 as HSPs were significantly differentially expressed here.…”

“…Expression patterns varied over the course of this experiment, but some expression patterns were maintained. In Montipora digitata , differential expression was apparent in stress related genes after a three day exposure to low pH but no impact was found over a 42 day exposure (González‐Pech et al., 2017), and in Acropora millepora subjected to low pH and high CO 2 no expression differences were detected in metabolism and calcification related genes after 14 days but one gene was downregulated after 37 days (Rocker et al., 2015).…”

Comparative Proteomics of Octocoral and Scleractinian Skeletomes and the Evolution of Coral Calcification

“…Peptides were mapped against respective octocoral ( Conci et al. 2019) and M. digitata ( González-Pech et al. 2017 ) transcriptomes.…”

Presence–absence polymorphisms of single-copy genes in the stony coral Acropora digitifera

“…In the third step, a single-copy gene of A. digitifera without high similarity in the previous step was used as a query for downstream tblastn searches [25]. CDSs of three Acroporidae species, Montipora aequituberculata, M. digitata [31], and Acropora tenuis were used to generate a database (Cnidaria database 2). A single-copy gene of A. digitifera with high similarity (cut-off e-value = 1e − 50 , identity ≥50%) to a CDS in Cnidaria database 2 and a highest similarity sequence from database 2 were retained for further analysis.…”