Unbiased high-throughput characterization of mussel transcriptomic responses to sublethal concentrations of the biotoxin okadaic acid
- Published
- Accepted
- Subject Areas
- Aquaculture, Fisheries and Fish Science, Marine Biology, Toxicology
- Keywords
- Okadaic Acid, Marine Pollution., Transcriptomics, Diarrhetic Shellfish Poisoning, Biomonitoring, Harmful Algal Blooms, Microarray
- Copyright
- © 2015 Suarez-Ulloa et al.
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ PrePrints) and either DOI or URL of the article must be cited.
- Cite this article
- 2015. Unbiased high-throughput characterization of mussel transcriptomic responses to sublethal concentrations of the biotoxin okadaic acid. PeerJ PrePrints 3:e1371v1 https://doi.org/10.7287/peerj.preprints.1371v1
Abstract
Background: Diarrhetic Shellfish Poisoning (DSP) Harmful Algal Blooms (HABs) represent a major threat for human consumers of shellfish. The biotoxin Okadaic Acid (OA), a well-known phosphatase inhibitor and tumor promoter, is the main responsible of acute DSP intoxications. Although several studies have described the molecular effects of high OA concentrations on sentinel organisms (e.g., bivalve molluscs), the effect of prolonged exposures to low (sublethal) OA concentrations is still unknown. In order to fill this gap, this work combines Next-Generation sequencing and custom-made microarray technologies to develop an unbiased characterization of the transcriptomic response of mussels during early stages of a DSP bloom. Methods: Mussel specimens were exposed to a HAB episode simulating an early stage DSP bloom (200 cells/L of the dinoflagellate Prorocentrum lima for 24 hours). Modifications in the expression of environmentally relevant transcripts were initially assessed using qPCR. The unbiased characterization of the transcriptomic responses triggered by OA was carried out using two complementary methods of cDNA library preparation: normalized and Suppression Subtractive Hybridization (SSH). Libraries were sequenced and read datasets were mapped to Gene Ontology and KEGG databases. A custom-made oligonucleotide microarray was developed based on these data, completing the expression analysis of digestive gland and gill tissues. Results: Our findings show that exposure to sublethal concentrations of OA is enough to induce gene expression modifications in the mussel Mytilus. Transcriptomic analyses revealed an increase in proteasomal activity, molecular transport, cell cycle regulation, energy production and immune activity in mussels. Oppositely, a number of transcripts hypothesized to be responsive to OA (notably the Serine/Threonine phosphatases PP1 and PP2A) failed to show substantial modifications. Both digestive gland and gill tissues responded similarly to OA, although expression modifications were more dramatic in the former, supporting the choice of this tissue for future biomonitoring studies. Discussion: Exposure to OA concentrations within legal limits for safe consumption of shellfish is enough to disrupt important cellular processes in mussels, eliciting sharp transcriptional changes as a result. By combining the study of cDNA libraries and a custom-made OA-specific microarray, our work provides a comprehensive characterization of the OA-specific transcriptome, improving the accuracy of the analysis of expresion profiles compared to single-replicated RNA-seq methods. The combination of our data with related studies helps understanding the molecular mechanisms underlying molecular responses to DSP episodes in marine organisms, providing useful information to develop a new generation of OA biomarkers.
Author Comment
This is a submission to PeerJ for review.
Supplemental Information
Primers used in qPCR
List of primers used for the expression analysis of environmentally relevant transcripts using qPCR.
Differentially expressed transcripts in digestive gland
List of differentially expressed transcripts with annotation found in digestive gland tissue showing an expression change greater than 100-fold (|logFC| > 2).
Differentially expressed transcripts in gill
List of differentially expressed transcripts with annotation found in gill tissue showing an expression change greater than 100-fold (|logFC| > 2).
GO terms in digestive gland
List of 20 Gene Ontology terms of the biological process category enriched (p-value < 0.05) for the set of upregulated transcripts in digestive gland tissue.
GO terms in gill
List of Gene Ontology terms of the biological process category enriched for the set of upregulated transcripts in gill tissue.
Upregulated metabolic pathways
List of active metabolic pathways with upregulated enzymes in digestive gland tissue.