Abstract
This study investigates for the first time the transcriptional regulation of a stress-inducible 70-kDa heat shock protein (hsp70) in the scleractinian coral Pocillopora verrucosa sampled at three locations and two depths (3 m and 12 m) in Bangka Island waters (North Sulawesi, Indonesia). Percentage of coral cover indicated reduced habitat suitability with depth and at the Tanjung Husi (TA) site, which also displayed relatively higher seawater temperatures. Expression of the P. verrucosa hsp70 transcript evaluated under field conditions followed a depth-related profile, with relatively higher expression levels in 3-m collected nubbins compared to the 12-m ones. Expression levels of metabolism-related transcripts ATP synthase and NADH dehydrogenase indicated metabolic activation of nubbins to cope with habitat conditions of the TA site at 3 m. After a 14-day acclimatization to common and fixed temperature conditions in the laboratory, corals were subjected for 7 days to an altered thermal regime, where temperature was elevated at 31°C during the light phase and returned to 28°C during the dark phase. Nubbins collected at 12 m were relatively more sensitive to thermal stress, as they significantly over-expressed the selected transcripts. Corals collected at 3 m appeared more resilient, as they showed unaffected mRNA expressions. The results indicated that local habitat conditions may influence transcription of stress-related genes in P. verrucosa. Corals exhibiting higher basal hsp70 levels may display enhanced tolerance towards environmental stressors.
Highlights
Anthropogenic stressors, such as climate changes, are driving relevant shifts in the abiotic features of marine ecosystems
Permutation t-tests showed that coral cover at 12 m was significantly reduced both at sites Sahoung 1 (SA1) and SA2, whereas no significant depth-related differences were at the site Tanjung Husi (TA), which showed the lowest percentage values at both depths (Fig 3)
To the best of our knowledge, this study investigated for the first time transcriptional stress responses in P. verrucosa that may underpin such physiological outputs, focusing on expression changes of a 70-kDa heat shock protein (Hsp70)
Summary
Anthropogenic stressors, such as climate changes, are driving relevant shifts in the abiotic features of marine ecosystems. Recent laboratory studies [3] and the discovery of natural populations resistant to extreme temperature events [15] or to naturally occurring hypercapnia [16] have shed new light on coral acclimatization and adaptive capabilities. These evidence lead to hypothesize that in such longlived organisms physiological acclimatization rather than genetic adaptation will play the leading role in their response to climate changes [3]
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