Characterisation of carbonic anhydrase in the symbiotic dinoflagellate Symbiodinium

• Main Author: Bobeszko, Teressa
• Format: Thesis
• Language: unknown
• Published: 2017
• Subjects: Ocean acidification
• Online Access: https://researchonline.jcu.edu.au/53111/1/53111-bobeszko-2017-thesis.pdf

Photosynthesis by Symbiodinium plays a central role in the coral-algal symbiosis as the majority (around 95%) of the hosts' metabolic demand is derived from photosynthetically fixed carbon. Photosynthesis in Symbiodinium is augmented by the use of a carbon-concentrating mechansism (CCM), of which the enzyme carbonic anhydrase (CA) plays a significant role in the accumulation, transportation and interconversion of inorganic carbon (Ci) forms to ultimately provide CO₂ for the carbon-fixing enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Environmental changes associated with climate change, such as ocean acidification and warming, represent key threats to coral reef ecosystems and are the major causes of the decline and deterioration of coral reefs worldwide and have prompted a major research focus on how climate related stressors affect coral-algal symbioses. Given the hosts' dependency on the symbionts ability to perform photosynthesis, how climate change will affect Symbiodinium photosynthesis is therefore an area that needs to be investigated. Current understanding of eukaryotic CCM expression is predominately derived from the green alga Chlamydomonas reinhardtii. While it has been demonstrated that Symbiodinium possess a CCM, the signals that trigger the expression of the CCM and subsequent genes involved have not been precisely defined in Symbiodinium. Therefore, the aims of this research were to use sequence tag data for Symbiodinium sp. Clade C3 to characterise the genes encoding CAs involved in the Symbiodinium CCM and to determine if Symbiodinium CAs were modified by external CO₂ concentrations as in other photosynthetic algae; to determine what the combined effects of elevated CO₂ and temperature were on Symbiodinium photosynthesis and CA expression; to examine varying light intensities on the regulation of CA; and to investigate possible long-term effects of CO₂ enrichment on the Symbiodinium transcriptome. To achieve these aims a sequencing project was performed. Bioinformatic ...