UNDERSTANDING TEMPERATURE ACCLIMATION IN SYMBIODINIUM: AN INTERDISCIPLINARY APPROACH

Open Access
Author:
Diaz Almeyda, Erika
Graduate Program:
Biology
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
May 07, 2015
Committee Members:
  • Monica Medina, Dissertation Advisor
Keywords:
  • Symbiodinium
  • temperature acclimation
  • transcriptomics
  • symbiosis
  • coral bleaching
  • global warming
  • climate change
Abstract:
I quantified the thermotolerance in 11 cultures from different populations of five species of Symbiodinium clade A. we grew cultures at 26°C and 32°C over 18 days, measuring growth and photochemical efficiency (Fv/Fm). Thermotolerance was not restricted to a single species but it was widespread across species and cultures, showing a gradient from susceptible to tolerant. All cultures at 32°C decreased growth and Fv/Fm. To test the synergistic effect of temperature and light, we cultured three strains (tolerant, intermediate, and susceptible) in five different light intensities at 26°C and 32°C. Strains surviving stressful light and temperature exhibited less growth and quicker damage by light. To investigate the mechanisms behind thermoacclimation, we cultured S. microadriaticum (CassKB8) with intermediate thermotolerance at 26°C and 32°C. Gene expression was explored first using cDNA microarrays before (day -2), and during acclimation (day 6 and 16). Differentially expressed genes (DEG) due to increased temperature were time dependent. DEG on day 16 were likely a result of the start of the stationary phase in culture. Similarly, RNA-Seq data (day 5 and 7) suggest temporal variation in gene expression with major changes in heat-shock proteins and chaperones. Retrotransposons were highly expressed on day 7, indicating high stress during thermal exposure. Adaptation to higher temperatures is not restricted to a single clade or species but it is widespread within species. However, acclimating to higher temperatures compromises health and increases chaperone activity.