Transcription of genes involved in bleaching of a coral reef species Acropora downingi (Wallace, 1999) in response to high temperature.

in Marine environmental research by Pegah Javid, Arash Akbarzadeh, Seyed Mehdi Alavi, Naser Farrokhi, Maryam Soyuf Jahromi, Siamak Behzadi, Mohammadreza Bakhtiarizadeh, Sajjad Pabasteh, Mohammad Sharif Ranjbar

TLDR

  • A study on Persian Gulf corals found that they exhibit remarkable resilience to elevated temperatures, with molecular responses indicating the expression of genes involved in heat shock proteins, oxidative stress, and calcification.
  • The study suggests that understanding the molecular mechanisms underlying this resilience can inform conservation efforts and provide insights into developing strategies to mitigate the impacts of climate change on coral reefs.

Abstract

Anthropogenic-induced global warming poses a significant threat to coral reef ecosystems worldwide. However, certain species within the Persian Gulf exhibit remarkable resilience to elevated temperatures compared to their counterparts in other reef systems. To understand the thermal tolerance in Persian Gulf corals and their molecular responses to extreme warm temperatures, Acropora downingi specimens collected from Larak Island were subjected to a heat shock of 34 ± 1 °C. We evaluated coral coloration, bleaching, and mRNA expression of biomarkers related to heat shock proteins (HSPs) such as Hsp70 and Hsp90, oxidative stress markers like Catalase and manganese superoxide dismutase (Cat and Mn-Sod), anti-apoptotic factors exemplified by B-cell lymphoma 2 (Bcl-2), and calcification-related genes including galaxin (Gal) after 24 h and 48 h of thermal shock exposure. Exposure of A. downingi to a 48-h heat shock at 34 °C resulted in noticeable fading of coral coloration compared to the control group. Despite this, the corals demonstrated resilience and did not undergo complete bleaching. Our findings also revealed significant increase of Hsp70, Hsp90, Cat, Mn-Sod, Bcl-2, and Gal mRNA expression after 24 h of thermal stress. However, after 48 h, transcripts for Hsp90, Cat, and Gal were observed to be decreased. These results suggest the pivotal roles played by genes involved in HSP signaling pathways, oxidative stress responses, anti-apoptosis processes, and calcification processes in the Persian Gulf coral's adaptation to thermal stress and its resistance to bleaching.

Overview

  • The study investigated the thermal tolerance of Acropora downingi coral species in the Persian Gulf, examining their molecular responses to extreme warm temperatures.
  • The researchers subjected coral specimens to a heat shock of 34 °C and evaluated coral coloration, bleaching, and mRNA expression of various biomarkers after 24 hours and 48 hours of thermal shock exposure.
  • The study aimed to understand the molecular mechanisms underlying the Persian Gulf coral's remarkable resilience to elevated temperatures compared to corals from other reef systems.

Comparative Analysis & Findings

  • Coral coloration faded noticeably after 48 hours of thermal shock exposure, but the corals did not undergo complete bleaching, demonstrating their resilience to thermal stress.
  • mRNA expression of heat shock proteins (HSPs), oxidative stress markers, anti-apoptotic factors, and calcification-related genes increased significantly after 24 hours of thermal stress, indicating a rapid response to thermal stress.
  • After 48 hours, transcripts for Hsp90, Cat, and Gal decreased, suggesting that the corals may have reached a threshold of thermal tolerance and adapted to the stress.

Implications and Future Directions

  • The study suggests that the Persian Gulf coral's remarkable resilience to thermal stress is attributed to its molecular responses, particularly the expression of genes involved in HSP signaling pathways, oxidative stress responses, anti-apoptosis processes, and calcification processes.
  • Future studies should investigate the specific mechanisms by which these gene networks contribute to the coral's thermal tolerance and explore ways to enhance this tolerance in other coral species.
  • Understanding the molecular basis of thermal tolerance in Persian Gulf corals can inform conservation efforts and provide insights into the development of strategies to mitigate the impacts of climate change on coral reefs worldwide.
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