Corals rely on photosynthesis by their endosymbiotic dinoflagellates ( Symbiodinium spp.) to form the basis of tropical coral reefs. High sea surface temperatures driven by climate change can trigger the loss of Symbiodinium from corals (coral bleaching), leading to declines in coral health. Different putative species (genetically distinct types) as well as conspecific populations of Symbiodinium can confer differing levels of thermal tolerance to their coral host, but the genes that govern dinoflagellate thermal tolerance are unknown. Here we show physiological and transcriptional responses to heat stress by a thermo-sensitive (physiologically susceptible at 32 (cid:2) C) type C1 Symbiodinium population and a thermo-tolerant (physiologically healthy at 32 (cid:2) C) type C1 Symbiodinium population. After nine days at 32 (cid:2) C, neither population exhibited physiological stress, but both displayed up-regulation of meiosis genes by (cid:3) 4-fold and enrichment of meiosis functional gene groups, which promote adaptation. After 13 days at 32 (cid:2) C, the thermo-sensitive population suffered a significant decrease in photosynthetic efficiency and increase in reactive oxygen species (ROS) leakage from its cells, whereas the thermo-tolerant population showed no signs of physiological stress. Correspondingly, only the thermo-tolerant population demonstrated up-regulation of a range of ROS scavenging and molecular chaperone genes by (cid:3) 4-fold and enrichment of ROS scavenging and protein-folding functional gene groups. The physiological and transcriptional responses of the Symbiodinium populations to heat stress directly correlate with the bleaching susceptibilities of corals that harbored these same Symbiodinium populations. Thus, our study provides novel, foundational insights into the molecular basis of dinoflagellate thermal tolerance and coral bleaching.
Sex, Scavengers, and Chaperones: Transcriptome Secrets of Divergent Symbiodinium Thermal Tolerances
R. A. Levin,V. Beltran,R. Hill,S. Kjelleberg,D. McDougald,P. Steinberg,Madeleine J. H. van Oppen
Published 2016 in Molecular biology and evolution
ABSTRACT
PUBLICATION RECORD
- Publication year
2016
- Venue
Molecular biology and evolution
- Publication date
2016-10-11
- Fields of study
Biology, Medicine, Environmental Science
- Identifiers
- External record
- Source metadata
Semantic Scholar, PubMed
CITATION MAP
EXTRACTION MAP
CLAIMS
CONCEPTS
- coral bleaching susceptibility
The tendency of corals to lose their Symbiodinium symbionts under stress and become bleached.
Aliases: bleaching susceptibility
- heat stress at 32 c
An elevated-temperature treatment at 32 C applied to the Symbiodinium populations in this experiment.
Aliases: 32 C heat stress, 32 C treatment
- meiosis genes
Genes associated with the meiotic cell-division program in Symbiodinium.
Aliases: meiotic genes
- molecular chaperone genes
Genes encoding chaperone proteins that help other proteins fold and remain stable.
Aliases: chaperone genes, protein-folding genes
- photosynthetic efficiency
A physiological measure of how effectively the Symbiodinium cells perform photosynthesis.
Aliases: PSII efficiency, photosynthesis efficiency
- reactive oxygen species leakage
The release of reactive oxygen species from Symbiodinium cells into the surrounding environment.
Aliases: ROS leakage
- ros scavenging genes
Genes involved in detoxifying or removing reactive oxygen species in Symbiodinium.
Aliases: reactive oxygen species scavenging genes, antioxidant genes
- thermo-sensitive type c1 symbiodinium population
The type C1 Symbiodinium population categorized as physiologically susceptible to elevated temperature.
Aliases: thermo-sensitive population, heat-sensitive type C1 population
- thermo-tolerant type c1 symbiodinium population
The type C1 Symbiodinium population categorized as physiologically healthy under elevated temperature.
Aliases: thermo-tolerant population, heat-tolerant type C1 population
- type c1 symbiodinium population
A genetically distinct Symbiodinium population classified as type C1 and used as one of the compared algal groups.
Aliases: C1 Symbiodinium population, type C1 population