Hsp60 expression profiles in the reef-building coral Seriatopora caliendrum subjected to heat and cold shock regimes Davide Seveso a, b, * , Simone Montano a, b , Giovanni Strona c , Ivan Orlandi a , Paolo Galli a, b , Marina Vai a a Department of Biotechnologies and Biosciences, University of Milan e Bicocca, Piazza della Scienza 2, 20126, Milan, Italy b MaRHE Centre (Marine Research and High Education Centre), Magoodhoo Island, Faafu Atoll, Maldives c European Commission, Joint Research Centre, Institute for Environment and Sustainability, Via E. Fermi 2749, I-21027, Ispra, Italy article info Article history: Received 19 February 2016 Received in revised form 2 May 2016 Accepted 7 May 2016 Available online 9 May 2016 Keywords: Hsp60 Down-regulation Global climate change Seriatopora caliendrum Cold stress Coral bleaching abstract Climate changes have increased the intensity/frequency of extreme thermal events, which represent serious threats to the health of reef-building corals. Since the vulnerability of corals exposed to thermal stresses are related to their ability to regulate Heat shock proteins (Hsps), we have analyzed together the time related expression profiles of the mitochondrial Hsp60 and the associated changes in tissue pigmentation in Seriatopora caliendrum subjected to 48 h of heat and cold treatments characterized by moderate (±2  C) and severe (±6  C) shocks. For the first time, an Hsp60 response was observed in a scleractinian coral exposed to cold stresses. Furthermore, the Hsp60 modulations and the changes in the tissue coloration were found to be specific for each treatment. A strong down-regulation at the end of the treatments was observed following both the severe shocks, but only the severe heat stress led to bleaching in concert with the lowest levels of Hsp60, suggesting that a severe heat shock can be more deleterious than an exposure to a severe cold temperature. On the contrary, a moderate cold stress seems to be more harmful than a moderate temperature increase, which could allow coral acclimation. Our results can provide a potential framework for understanding the physiological tolerance of corals under possible future climate changes. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction The environmental stresses associated with climate change are widely recognized as the most serious threat to the health of coral reefs (Hughes et al., 2003; Pandolfi et al., 2003; Hoegh-Guldberg et al., 2007; Grottoli et al., 2014). Over recent decades, climate shifts have intensified thermal stresses on corals, with an increase in the frequency and severity of bleaching events that have led to a worldwide decline in coral cover and dramatic changes in coral community structure (Hughes et al., 2007; Hoegh-Guldberg and Bruno, 2010; Montano et al., 2010; De’ath et al., 2012). In fact, although coral bleaching, namely the loss of endosymbionts and/or their photosynthetic pigments, occurs in response to several abiotic stressors (reviewed in Lesser, 2011), the main coral bleaching epi- sodes that have resulted in significant mortality are strongly correlated with elevated sea temperatures (Brown, 1997; Goreau et al., 2000; Smith et al., 2008; Van Woesik et al., 2011; Alemu and Clement, 2014). Reef-building corals live close to their upper thermal limits and may experience heat stress and bleaching once exposed to long-term (days-weeks) seawater temperature in- creases of only 1e2  C as well as a short-term (hours-days) but intense thermal rise (Jokiel and Coles, 1990; Hoegh-Guldberg,1999; Fitt et al., 2001). Sea surface temperatures are expected to increase rapidly from 1.8 to 4.0  C above the current mean by 2100 (Sheppard and Rioja-Nieto, 2005; IPCC, 2007). Therefore, the proven sensitivity of corals to these projected temperature changes poses the problem of how they will respond to this warming trend (Pandolfi et al., 2011). Climate change, however, may also lead to strong and rapid thermic fluctuations linked to the cooling of the water column due to the passage of polar continental air masses, or to upwelling events and large-amplitude internal waves (Leichter et al., 2006; Schmidt et al., 2012; Wall et al., 2014; Buerger et al., 2015). Many reefs experienced daily temperature oscillations greater than 10  C * Corresponding author. Department of Biotechnologies and Biosciences, Uni- versity of Milan e Bicocca, Piazza della Scienza 2, 20126, Milan, Italy. E-mail address: davide.seveso@unimib.it (D. Seveso). Contents lists available at ScienceDirect Marine Environmental Research journal homepage: www.elsevier.com/locate/marenvrev http://dx.doi.org/10.1016/j.marenvres.2016.05.007 0141-1136/© 2016 Elsevier Ltd. All rights reserved. Marine Environmental Research 119 (2016) 1e11