Transcriptomic characterization of the enzymatic antioxidants FeSOD, MnSOD, APX and KatG in the dinoflagellate genus Symbiodinium

Krueger, Thomas, Fisher, Paul L., Becker, Susanne, Pontasch, Stefanie, Dove, Sophie, Hoegh-Guldberg, Ove, Leggat, William and Davy, Simon K (2015) Transcriptomic characterization of the enzymatic antioxidants FeSOD, MnSOD, APX and KatG in the dinoflagellate genus Symbiodinium. BMC Evolutionary Biology, 15 1: 48.1-48.20. doi:10.1186/s12862-015-0326-0


Author Krueger, Thomas
Fisher, Paul L.
Becker, Susanne
Pontasch, Stefanie
Dove, Sophie
Hoegh-Guldberg, Ove
Leggat, William
Davy, Simon K
Title Transcriptomic characterization of the enzymatic antioxidants FeSOD, MnSOD, APX and KatG in the dinoflagellate genus Symbiodinium
Formatted title
Transcriptomic characterization of the enzymatic antioxidants FeSOD, MnSOD, APX and KatG in the dinoflagellate genus Symbiodinium
Journal name BMC Evolutionary Biology   Check publisher's open access policy
ISSN 1471-2148
Publication date 2015-03-18
Sub-type Article (original research)
DOI 10.1186/s12862-015-0326-0
Open Access Status DOI
Volume 15
Issue 1
Start page 48.1
End page 48.20
Total pages 20
Place of publication London, United Kingdom
Publisher BioMed Central
Collection year 2016
Language eng
Formatted abstract
Background: The diversity of the symbiotic dinoflagellate Symbiodinium sp., as assessed by genetic markers, is well established. To what extent this diversity is reflected on the amino acid level of functional genes such as enzymatic antioxidants that play an important role in thermal stress tolerance of the coral-Symbiodinium symbiosis is, however, unknown. Here we present a predicted structural analysis and phylogenetic characterization of the enzymatic antioxidant repertoire of the genus Symbiodinium. We also report gene expression and enzymatic activity under short-term thermal stress in Symbiodinium of the B1 genotype.

Results: Based on eight different ITS2 types, covering six clades, multiple protein isoforms for three of the four investigated antioxidants (ascorbate peroxidase [APX], catalase peroxidase [KatG], manganese superoxide dismutase [MnSOD]) are present in the genus Symbiodinium. Amino acid sequences of both SOD metalloforms (Fe/Mn), as well as KatG, exhibited a number of prokaryotic characteristics that were also supported by the protein phylogeny. In contrast to the bacterial form, KatG in Symbiodinium is characterized by extended functionally important loops and a shortened C-terminal domain. Intercladal sequence variations were found to be much higher in both peroxidases, compared to SODs. For APX, these variable residues involve binding sites for substrates and cofactors, and might therefore differentially affect the catalytic properties of this enzyme between clades. While expression of antioxidant genes was successfully measured in Symbiodinium B1, it was not possible to assess the link between gene expression and protein activity due to high variability in expression between replicates, and little response in their enzymatic activity over the three-day experimental period.

Conclusions: The genus Symbiodinium has a diverse enzymatic antioxidant repertoire that has similarities to prokaryotes, potentially as a result of horizontal gene transfer or events of secondary endosymbiosis. Different degrees of sequence evolution between SODs and peroxidases might be the result of potential selective pressure on the conserved molecular function of SODs as the first line of defence. In contrast, genetic redundancy of hydrogen peroxide scavenging enzymes might permit the observed variations in peroxidase sequences. Our data and successful measurement of antioxidant gene expression in Symbiodinium will serve as basis for further studies of coral health.
Keyword Antioxidant gene expression
Ascorbate peroxidase
Catalase peroxidase
Coral reefs
Oxidative stress
ROS
Superoxide dismutase
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

 
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