11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 5: Functional Biology of Corals and Coral Symbiosis: Molecular Biology, Cell Biology and Physiology
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Suicide Is Painless, It Brings On Many Changes: Apoptosis And Autophagy in
Cnidarian-Dinoflagellate Symbiosis.
Simon DUNN* 1 , Sophie DOVE 1
1 Center for Marine Studies, University of Queensland, St Lucia, Brisbane, Australia
The underlying cellular pathways that control the onset, maintenance and breakdown of
cnidarian–dinoflagellate symbiosis are just beginning to be described. The pathways that
have been shown to operate during these processes are highly conserved from yeast to
complex metazoans, including higher vertebrates. Two examples of these pathways are
apoptosis and autophagy, which are crucial to development, tissue homeostasis and
immunity. Apoptosis and autophagy leading to the suicide of specific cells has been
shown to be active when the cnidarian-dinoflagellate symbiosis is under stress. Key
molecular components of these signal transduction pathways have been identified in
cnidarians. However, the triggers activating the initiation of these pathways in this
symbiosis remain unresolved and are now under investigation. This study focuses on the
role of mitochondria in these cellular processes.
5-27
Potential Parental Effects On Establishment And Maintenance Of Cnidarian-Algal
Symbioses
Daniel POLAND* 1 , Andrew HANNES 1 , Mary Alice COFFROTH 2
1 Department of Biological Sciences, SUNY at Buffalo, Buffalo, NY, 2 Department of
Geology, SUNY at Buffalo, Buffalo, NY
During early stages of cnidarian-algal symbioses coral recruits acquire a diverse array of
symbiotic dinoflagellate algae (genus Symbiodinium). Yet over time Symbiodinium
diversity within the host is reduced as the adult host-Symbiodinium specificity is
established. The factors controlling this are unclear. Here, we investigated the
establishment of symbioses between a Caribbean octocoral, Briareum asbestinum, and its
Symbiodinium partners. Adult B. asbestinum harbor Symbiodinium of two lineages within
clade B (B178 and B184), which are distinguished by sequence variability in the
chloroplast large subunit (23S) ribosomal DNA. B. asbestinum harbored Symbiodinium
B178 in most Caribbean and Florida Keys populations sampled. However, in the Florida
Keys, a few B. asbestinum populations harbored mostly B184 or B178+B184
Symbiodinium. To investigate the progression of the symbiosis from newly settled polyps
(recruits) to established colonies, asymbiotic larvae were collected from parents with
B184 or B178 Symbiodinium. Larvae from B178 adults were placed in several habitats
and larvae from B184 adults were raised at a site where only B178 adults were found.
Regardless of the Symbiodinium populations in adults, recruits initially harbored
Symbiodinium assemblages dominated by B184, although other algal symbionts were
also present. After 24 months, 98% of recruits originating from parents with B184
Symbiodinium harbored only B184, despite the predominance of B178 in the local host
population. Recruits originating from parents with B178 Symbiodinium showed an
increased frequency of B178 with 10% and 40% of the recruits harboring B178 and
B178+184, respectively, and 50% maintaining only B184 Symbiodinium. These results
suggest that establishment of symbiotic relationships in cnidarians may remain dynamic
for many years following settlement and initial Symbiodinium acquisition.
5-28
Cell-Cycle Regulation in The Dinoflagellate-Cnidarian Symbiosis
Santiago PEREZ* 1 , John PRINGLE 1 , Carlo CARUSO 1
1 Genetics, Stanford, Stanford, CA
Studies of cnidarian-algal symbiosis have described many aspects of their anatomy and
physiology. However, to date, the molecular and cellular underpinnings of these ecologically
important symbioses remain grossly understudied. For example, several studies of the
hydrozoan species Hydra viridis concluded that its symbiotic green-algal cells coordinate
their cell cycles with those of the host cells and that light, inorganic nutrients, and host feeding
are important regulators of this process. Yet, we do not know the mechanisms either of hostsymbiont
coordination or of the environmental influences on the process, nor is it clear whether
the controls that appear to operate in Hydra are also found in other systems such as coraldinoflagellate
symbioses. We are one of several laboratories attempting to develop the small
tropical sea anemone Aiptasia spp. as a tractable laboratory model system for study of the
molecular and cell biology of cnidarian-dinoflagellate symbioses. Aiptasia, like the
scleractinian corals, is symbiotic with dinoflagellates of the genus Symbiodinium, so it is
likely that our results will be widely applicable. We will describe our progress in developing
methods for the study of and in elucidating the coordination between the host and symbiont
cellular reproduction during the initial establishment of the symbiosis, its steady-state
maintenance, and the stress conditions that lead to the breakdown of the symbiois.
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Functional Diversity in The Symbiotic Interactions Between Coral And symbiodinium
Michael STAT* 1 , Emily MORRIS 1 , Ruth GATES 1
1 HIMB, University of Hawaii, Kaneohe, HI
The symbiotic continuum ranges between mutualism and parasitism. In coral-dinoflagellate
symbiosis, the interaction has been defined as mutualistic via the exchange of organic and
inorganic nutrients that in turn allows for the growth and formation of coral reefs. The
symbiotic dinoflagellate genus Symbiodinium is genetically diverse containing eight broad
lineages (clades A-H). Corals predominantly associate with clade C Symbiodinium, and less
commonly with clades A, B, D, F, and G. Variation in the function and interactive physiology
of different coral-dinoflagellate assemblages is virtually unexplored but important to our
understanding of factors that contribute to coral reef resilience. In this study, we evaluated the
symbiotic interaction between coral and Symbiodinium belonging to two clades, A and C. We
approached this using ecological, phylogenetic, and biochemical analyses. Our data shows 1)
that there is a significant correlation between the presence of Symbiodinium clade A and
health compromised corals; 2) that phylogenetic and genetic distance analyses place clade A as
more closely related to free-living dinoflagellates than the other Symbiodinium lineages; and
3) that Symbiodinium clade A fixes and releases significantly lower amounts of carbon in the
presence of a coral synthetic host factor than clade C. Collectively these data demonstrate that
the interaction between coral and Symbiodinium clade A is not the same as the relationship
between clade C and coral and that along the symbiotic continuum the interaction between
clade A and coral is closer to parasitic than mutualistic in nature.
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