11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 6: Ecological and Evolutionary Genomics of Coral Reef Organisms
6-6
Coral Reef Genomics: A Genome Wide Approach To Study Establishment And
Maintenance Of Coral-Zooxanthellae Symbioses
Christian VOOLSTRA* 1 , Jodi SCHWARZ 2 , Mary Alice COFFROTH 3 , Alina M.
SZMANT 4 , Mónica MEDINA 5
1 School of Natural Sciences, University of California, Merced, Merced, CA, 2 Vassar
College, Poughkeepsie, NY, 3 State University of New York at Buffalo, Buffalo, NY,
4 UNCW-Center for Marine Science, Wilmington, NC, 5 University of California, Merced,
Merced, CA
Symbioses between scleractinian corals and their photosynthetic unicellular symbionts
(dinoflagellates or zooxanthellae) form the basis of coral reef ecosystems. While the
importance of this mutualistic relationship is well documented, surprisingly little is
known about the cellular processes involved in the establishment and maintenance of this
partnership.
We use large scale gene expression profiling (microarrays) to study the transcriptomic
changes in two Caribbean reef building coral species (Montastraea faveolata and
Acropora palmata) in response to infection with different strains of zooxanthellae. A
high number of genes change expression upon infection; and genes involved in signal
transduction, cytoskeletal activity, metabolism and energy production, and stress are
modified. In contrast, only a few differences exist upon infection with different
zooxanthella strains.
These data indicate that although there is a profound change in coral
physiology upon establishment of symbiosis, an evolutionarily conserved
mechanism of establishment of symbiosis exists.
6-7
Differential Gene Expression During Thermal Stress And Bleaching in The
Caribbean Coral montastraea Faveolata
Michael DESALVO* 1 , Christian VOOLSTRA 1 , Shinichi SUNAGAWA 1 , Jodi
SCHWARZ 2 , Mary Alice COFFROTH 3 , Alina SZMANT 4 , Mónica MEDINA 1
1 School of Natural Sciences, University of California, Merced, Merced, CA, 2 Department
of Biology, Vassar College, Poughkeepsie, NY, 3 Graduate Program in Evolution,
Ecology, and Behavior, State University of New York at Buffalo, Buffalo, NY, 4 Center
for Marine Science, University of North Carolina, Wilmington, Wilmington, NC
The declining health of coral reefs worldwide is likely to intensify in response to
continued anthropogenic disturbance from coastal development, pollution, and climate
change. Reef-building corals respond to stress by bleaching, in which their symbiosis
with zooxanthellae collapses. Mass coral bleaching in response to elevated water
temperature can devastate coral reefs on a huge geographic scale. In order to understand
the molecular and cellular basis of thermal bleaching in corals, we have taken a
transcriptomic approach. cDNA microarrays, containing features representing 1,310
genes of the Caribbean coral Montastraea faveolata, were utilized to measure gene
expression changes associated with thermal stress and bleaching. Thermal stress
experiments were conducted in temperature-controlled aquaria, and bleaching was
elicited by increasing the temperature by 3oC above normal. Differentially expressed
genes were identified in two separate experiments: the first experiment compared gene
expression between control fragments and partially bleached fragments; and the second
experiment compared control fragments to heat stressed fragments along a time course
ending at partial bleaching. Our findings suggest that thermal stress and bleaching in M.
faveolata results in: heat shock protein expression, oxidative stress, re-organization of
the cytoskeleton, disruption of Ca2+ homeostasis, decreased calcification, metabolism,
and protein synthesis, increased activity of transposons and defensin-like peptides, and
the initiation of cell death. We believe that oxidative stress in heat-stressed corals results
in a disruption of cellular Ca2+ homeostasis, which leads to cytoskeletal and cell
adhesion changes, decreased calcification, and the initiation of cell death via apoptosis
and necrosis.
6-8
An Ecological Microarray Study Of Coral Bleaching
Francois SENECA 1,2 , Francois SENECA* 1,2 , Sylvain FORET 3 , Nicolas GOFFARD 4 , Carolyn
SMITH 2 , Lauretta GRASSO 3 , David HAYWARD 3 , Robert SAINT 3 , Madeleine VAN OPPEN 2 ,
Eldon BALL 3 , David MILLER 1,3
1 ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville 4811,
Townsville, Australia, 2 Australian Institute of Marine Science, Townsville 4810, Townsville,
Australia, 3 ARC Centre for the Molecular Genetics of Development, Australian National
University, Canberra 2601, Canberra, Australia, 4 Louis Malardé Institute, Papeete 98713,
Papeete, French Polynesia
Reef building corals live close to their upper thermal tolerance limit and prolonged exposure to
temperatures exceeding 31°C induces coral bleaching – the expulsion of Symbiodinium sp.
which is often the first step toward mass mortality. Current projections suggest that average
tropical ocean temperatures could warm by 1-3°C by the end of this century, so unless corals
have the capacity for adaptation to anthropogenically induced climate change, those species that
survive are likely to undergo dramatic shifts in distribution patterns. To investigate coral stress
responses at a fundamental level we used microarrays of approximately 17,000 expressed
sequence tags (ESTs) from the hermatypic coral Acropora millepora to attempt to identify
genes responsible for individual fitness and the capacity to survive.
Bleaching responses have traditionally been investigated largely by subjecting corals to acute
thermal stress in vitro. Our approach has focussed on several coral colonies growing in a single
bay that have been sampled in situ through a natural bleaching episode and the subsequent
recovery period. During the sampling period, water temperature was continuously monitored (at
15 min intervals) and symbiont density recorded at monthly intervals as a measure of bleaching
status.
Individual colonies differed dramatically in their overall responses to similar environmental
conditions – the extent of reduction of symbiont density varied considerably and, whereas some
colonies recovered after the summer period, others died. Microarray experiments on a subset of
colonies, which showed similar patterns of symbiont loss, identified a large number of genes
with expression significantly correlated to decreases in symbiont density. The implications of
these experiments in terms of understanding the mechanisms by which corals respond during
bleaching episodes will be discussed.
6-9
Bacterial Community And Gene Expression Profiling Using 16srrna Gene And Cdna
Microarrays: Introduction Of A Dual High-Throughput Approach To The Study Of
Coral Disease And Bleaching
Shinichi SUNAGAWA* 1 , Paul FISHER 2 , Michael DESALVO 1 , Christian VOOLSTRA 1 ,
Ernesto WEIL 3 , Gary ANDERSEN 4 , Roberto IGLESIAS-PRIETO 2 , Mónica MEDINA 1
1 School of Natural Sciences, University of California Merced, Merced, CA, 2 Unidad Académica
de Sistemas Arrecifales ICML-UNAM, Universidad Nacional Autónoma de México, Puerto
Morelos, Mexico, 3 Department of Marine Science, University of Puerto Rico, Mayagüez,
Puerto Rico, 4 Center for Environmental Biotechnology, Lawrence Berkeley National
Laboratory, Berkeley, CA
Increasing evidence highlights the fact that bacteria play a crucial role within coral holobiont,
i.e. the coral host and its associated microbial communities. Current approaches to describe the
bacterial diversity in corals involve the universal amplification of bacterial 16SrRNA gene via
the polymerase chain reaction (PCR) with subsequent analysis by terminal-restriction fragment
length polymorphism (t-RLFP), temperature/denaturing gradient gel electrophoresis (T/DGGE),
or sequencing of recombinant 16SrDNA clone libraries. Analyzing the expression of one or a
few genes in coral samples may be accomplished through quantitative PCR. However, largescale
comparative studies with the aim to discover statistical differences in bacterial species
composition as well as global changes in the coral transcriptome would require the application
of more efficient high-throughput technologies. In light of increasing frequencies of coral
disease and bleaching events, it is imperative to gain a better understanding of (a) concomitant
changes in coral-associated bacterial communities and (b) the molecular responses of coral
hosts to such stress events. Here, we introduce the application of 16SrRNA gene microarrays in
combination with coral host cDNA microarrays to simultaneously profile both changes in
microbial community composition and coral gene expression. Specifically, we are comparing
healthy versus both diseased and bleached corals using the Caribbean coral species
Montastraea faveolatea as a model system. This approach applies statistical tools to identify
differentially abundant bacteria in diseased or bleached coral samples and aims to identify genes
or gene pathways that are involved in the immune as well as thermal stress response of corals.
The expected results may validate the application of these high-throughput tools as a versatile
platform for monitoring and assessing the health status of corals, and thus could guide their
implementation for effective management strategies to preserve coral reefs.
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