S. Franzellitti, V. Airi, D. Calbucci, E. Caroselli, F. Prada, C.R. Voolstra, T. Massd, G. Falinie, E. Fabbria, S. Goffredo
Marine Environmental Research, (2018)
Thermal stress, Coral, Gene expression, Heat shock protein, Physiological plasticity, Climate change
Shallow-water corals of the Mediterranean Sea are facing a dramatic increase in water temperature due to
climate change, predicted to increase the frequency of bleaching and mass mortality events. However, supposedly
not all corals are affected equally, as they show differences in stress susceptibility, as suggested by physiological
outputs of corals along temperature gradients and under controlled conditions in terms of reproduction,
demography, growth, calcification, and photosynthetic efficiency. In this study, gene expression and
induction of a 70-kDa heat shock protein (HSP70) was analyzed in five common shallow-water hard corals in the
Mediterranean Sea, namely Astroides calycularis, Balanophyllia europaea, Caryophyllia inornata, Cladocora caespitosa,
and Leptopsammia pruvoti. The main aim was to assess the contribution of this evolutionary conserved
cytoprotective mechanism to the physiological plasticity of these species that possess different growth modes
(solitary vs colonial) and trophic strategies (zooxanthellate vs azooxanthellate). Using quantitative real-time
PCR, in situ hsp70 baseline levels and expression profiles after a heat-shock exposure were assessed.
Levels of hsp70 and heat stress induction were higher in zooxanthellate than in azooxanthellate species, and
different heat stress transcriptional profiles were observed between colonial and solitary zooxanthellate corals.
On the whole, the hsp70 transcriptional response to heat stress aligns with stress susceptibility of the species and
suggests a contribution of trophic strategy and morphology in shaping coral resilience to stress. Understanding
these molecular processes may contribute to assess the potential effects and relative resilience of Mediterranean
corals under climate change.