11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 6: Ecological and Evolutionary Genomics of Coral Reef Organisms
6-18
Examining The Genetic Basis Of Coral Morphospecies: Testing The Core Genome
Hypothesis With Microarrays
Jason LADNER* 1 , Madeleine VAN OPPEN 2 , Stephen PALUMBI 1
1 Hopkins Marine Station, Stanford University, Pacific Grove, CA, 2 Marine Microbiology
and Symbiosis, Australian Institute of Marine Science, Townsville, Australia
With extensive cross-specific fertility and multi-species synchronized mass spawning
events, reef corals represent an animal taxon unparalleled for its potential for interspecific
hybridization. Yet, in the face of potentially homogenizing gene flow between species,
high species diversity with extensive sympatry is maintained. One possible explanation is
that the morphospecies we recognize are each defined by a core set of genes that must
remain together while other regions of the genome can be freely exchanged between
species. High-density oligonucleotide microarrays provide a powerful tool to test the core
genome hypothesis by allowing rapid, fine-scale genome-wide interrogation of sequence
similarity between coral species. We designed an array using the publicly available
Acropora millepora expressed sequence tag (EST) library to investigate the genomic
similarity of two highly cross-fertile coral species: Acropora millepora and A. pulchra.
The arrays consisted of 21,576 unique 60 base pair probes. Twelve individuals from each
species were hybridized separately to the array along with a common reference. Results
show that 46% of the array probes (9945 of 21,576), speckled across 75% of the ESTs
included on the array (4635 of 6156), show significant hybridization differences between
A. millepora and A. pulchra. These probes identify regions that likely exhibit little to no
introgression between these species, and therefore, may be responsible for the
morphological and physiological differences between them. If confirmed, these results
would suggest the core genome for these species is quite large. Additionally, this
technique produces a hybridization intensity ‘barcode’ for each individual that has proven
to be reliable for species identification, a task single gene techniques have often failed at
in corals.
6-19
Variation in Gene Expression Within And Among Acropora Millepora Populations
On The Great Barrier Reef.
Line K BAY* 1 , Karin E ULSTRUP 2 , H Bjorn NIELSEN 3 , Bette WILLIS 1,4 , David J
MILLER 1,5 , Madeleine VAN OPPEN 6
1 ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville,
Australia, 2 Marine Biological Laboratory, University of Copenhagen, Helsingor,
Denmark, 3 Centre for Biological Sequence Analysis, Danish Technical University,
Lyngby, Denmark, 4 School of Marine and Tropical Biology, James Cook University,
Townsville, Australia, 5 Biochemistry and Molecular Sciences, James Cook University,
Townsville, Australia, 6 Australian Institute of Marine Science, Townsville, Australia
Gene expression is a fundamental link between the genetic make-up of an organism
(genotype) and how it functions in its environment (phenotype) and, when correlated
with biological and environmental variables, can provide novel insights into the ecology,
evolution and health status of the target organism. Here we used a specific cDNA
microarray to investigate natural variation in global gene expression within and among
populations of A. millepora, a common reef-building coral on the GBR. We examined the
roles of acclimatization and adaptation by comparing patterns of gene expression of field
sampled coral colonies from two populations with different thermal environments and
bleaching histories, with that following a ten-day acclimation in a common environment.
ANOVA analyses revealed that four genes were differentially expressed between
Populations (p < 3.86 x 10-6; median absolute fold change (MAFC) = 0.99), 114 between
sampling Locations (field vs lab) (p < 2.48 x 10-5; MAFC = 1.04) and six in the
Population by Location interaction (p < 8.01 x 10-5; MAFC = 1.42). The significant
location genes represented a range of functional groups and clustered into three
expression profiles. These results suggest that A. millepora have substantial potential to
up and down-regulate genes through acclimatization when ambient environmental
conditions change. We also found potential for local adaptation in gene expression under
natural conditions in a few genes in the Population and Population x Location treatments.
Because many additional genes displayed large MAFC (>1.5) but low statistical
significance in these treatments (No. genes: Population = 14, Population x Location =
51), it is possible that inter-colony variation obscured our ability to detect local
adaptation in such genes. We examine inter and intra-colony variation in gene expression
in this species in a subsequent experiment.
6-20
Sponge Paleogenomics And The Evolution Of Biocalcification
Gert WORHEIDE* 1 , Luciana MACIS 1 , Joachim REITNER 1 , Bernard M. DEGNAN 2 , Daniel
J. JACKSON 1,2
1 Courant Research Center Geobiology, University of Gottingen, Gottingen, Germany, 2 School
of Integrative Biology, University of Queensland, Brisbane, Australia
The ability to regulate the formation of calcified structures was a key metazoan innovation
during the late Precambrian that have, for example, enabled the subsequent development of reef
structures throughout the Earth’s history until present. However, the evolution of the
biosynthetic pathways of biocalcification remain largely enigmatic and it is unknown to what
extent the last common ancestor of the Metazoa (LCAM) provided the genetic tools to enable
biomineralisation. Sponges, the most ancestral-like metazoans, were prolific calcifying and
reef-building organisms during the Paleozoic and Mesozoic, and some of those taxa survive
today. We have studied one such 'living fossil', the demosponge Astrosclera willeyana which
possesses a calcareous basal skeleton, and applied a paleogenomics approach to show that a key
molecular component of this biomineralisation-toolkit was the precursor to the diverse αcarbonic
anhydrase (α-CA) gene family, one of the most physiologically important and catalytic
enzymes known. We show that α-CAs expanded through several independent gene duplication
events in sponges and eumetazoans, and that these coralline sponges inherited key components
of the first multicellular skeletogenic toolkit from the LCAM. Furthermore, with recent whole
genome sequencing efforts of various metazoans, EST collections and targeted gene studies,
examples of conserved and lineage specific biocalcification genes are gradually being
identified. In some cases we are now able to infer what skeletogenic genes may have been
present in the LCAM and discuss this in the context of the evolution of metazoan
biocalcification mechanisms and their resilience to ocean acidification.
6-21
Coral Kin Aggregations Exhibit Mixed Allogeneic Reactions And Enhanced Fitness
During Early Ontogeny
Keren-Or AMAR* 1,2 , Nanette CHADWICK 3 , Baruch RINKEVICH 1
1 Biology, Israel Oceanographic and Limnological Research (IOLR), Haifa, Israel, 2 The Mina
and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, Israel,
3 Biological Sciences, Auburn University, Auburn, AL
Only sparse information exists on the selective forces and ecological consequences of
aggregated settlement and chimera formation by kin larvae in marine invertebrates. Kin larvae
of the reef-building coral Stylophora pistillata settle in aggregations. Upon contact, recruits
either fuse, establishing a chimera, or reject one another. Our one-year study on growth and
survival of 544 genotypes revealed six types of biological entities: single genotypes, bichimeras,
bi-rejecting genotypes, tri-chimeras, tri-rejecting genotypes, and multi-partner
entities. Analysis of allorecognition responses revealed an array of effector mechanisms from
true tissue fusion, transitory fusion, borderline formation, and overgrowth, to rejection and
partner death; all with complex ontogeny. We found that young multi-partner entities were the
largest. However, at the genotype level, single genotype entities were the largest. Survival rates
did not vary significantly among entities, but multi-partner entities exhibited the highest
survival rate and single genotypes the lowest. We propose that a driving force for this
gregarious kin settlement stems from benefits associated with the increased total size of the
entity, forming biological organizations that exhibit, simultaneously, intricate networks of
rejecting and fusible interactions.
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