Transcriptional responses of heat shock protein 70 (Hsp70) to thermal, bisphenol A, and copper stresses in the dinoflagellate Prorocentrum minimum R. Guo, V. Ebenezer, J.-S. Ki ⇑ Department of Green Life Science, Sangmyung University, Seoul 110-743, Republic of Korea highlights " Toxicogenomic response of Hsp70 in the dinoflagellate Prorocentrum minimum. " Putative PmHsp70 contained three signature patterns of the Hsp70 family. " EC 50 s are 1.1 mg L À1 copper and 1.5 mg L À1 biophenol A in P. minimum. " PmHsp70 was significantly upregulated by thermal, Cu, and BPA exposures. " Demonstration of the Hsp70 response in the dinoflagellate to thermal and toxic stress. article info Article history: Received 7 November 2011 Received in revised form 20 April 2012 Accepted 3 May 2012 Available online 21 June 2012 Keywords: PmHsp70 Prorocentrum minimum Gene expression Toxic Environmental stress abstract The heat shock protein 70 (Hsp70) family is an important part of the cell’s machinery for protein folding, and helps to protect cells from environmental stress. Although Hsp70 functions have been discovered in various organisms, studies on dinoflagellate Hsps are limited, except for a few phylogenetic attempts. In this study, we sequenced the complete open reading frame of the dinoflagellate Prorocentrum minimum Hsp70 (PmHsp70), and characterized its molecular functions. The putative PmHsp70 protein contained 3 signature patterns of the Hsp70 family. Phylogenetic analysis revealed that PmHsp70 belonged to the dinoflagellate clade. Real-time (RT)-PCR analyses revealed that PmHsp70 was upregulated by thermal stress. Further, we examined the transcriptional response of PmHsp70 to copper (Cu) and bisphenol A (BPA) exposures. In toxicity assays, Cu and BPA exhibited EC 50 -72 h values of 1.07 ± 0.138 mg L À1 and 1.51 ± 0.110 mg L À1 , respectively, in P. minimum. Expression of PmHsp70 was significantly upregulated in response to Cu and BPA exposures (one-way ANOVA, P < 0.05). PmHsp70 displayed different expression patterns in response to different concentrations of Cu and BPA. This study evaluated typical characteris- tics and, for the first time, toxicant-related functions of PmHsp70. The results suggest that Hsp70 genes may play a vital role in the environmental stress responses of dinoflagellates. Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved. 1. Introduction Dinoflagellates are the primary producers in aquatic ecosys- tems; they are highly diversified, with more than 4500 species and 550 genera identified till date, according to the Tree of Life Web Project (http://tolweb.org/tree/). Dinoflagellates include organisms of interest (e.g., Akashiwo, Alexandrium, Karenia, Pfieste- ria, and Prorocentrum) for eukaryotic evolutionary studies and, as toxic algae, for their impact on human health and fisheries. As uni- cellular eukaryotes, dinoflagellates have distinct genomic features (Taylor, 1987; Hackett et al., 2005; Moreno Díaz de la Espina et al., 2005; Moustafa et al., 2010). For instance, they possess a large amount of DNA, ranging from 1.5 to 225 pg per cell (LaJeunesse et al., 2005), and their chromosomes remain permanently con- densed during the entire cell cycle (Taylor, 1987; Moreno Díaz de la Espina et al., 2005). The dinoflagellate nuclear DNA is exten- sively methylated, and 12–70% of thymine is replaced by 5-hydroxymethyluracil (Lin, 2011). The genes expressed in dino- flagellates are trans-spliced in nuclear mRNA processing reactions (Zhang et al., 2007). The expression of S-phase proteins in certain dinoflagellates (e.g., Karenia brevis) is independent of transcription upon entry into the S-phase, but appears to be under post- transcriptional control (Brunelle and Van Dolah, 2011). In recent years, dinoflagellate gene regulation and expression studies have been performed using expressed sequence tags (ESTs) or global gene expression profiles (Okamoto and Hastings, 2003; Hackett et al., 2005; Moustafa et al., 2010). These EST analyses indicate that many dinoflagellate genes possess a high copy number and display a certain degree of diversity between these copies (Bachvaroff and 0045-6535/$ - see front matter Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.chemosphere.2012.05.014 ⇑ Corresponding author. Tel.: +82 2 2287 5449; fax: +82 2 2287 0070. E-mail address: kijs@smu.ac.kr (J.-S. Ki). Chemosphere 89 (2012) 512–520 Contents lists available at SciVerse ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere