11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 6: Ecological and Evolutionary Genomics of Coral Reef Organisms
6-22
Chimera Formation During The Early Life History Of Acropora Millepora And Its
Persistence Through Time
Eneour PUILL-STEPHAN* 1,2 , Bette WILLIS 1 , Madeleine VAN OPPEN 2 , Lynne VAN
HERWERDEN 1
1 James Cook University, Townsville, Australia, 2 Australian Institute of Marine Science,
Townsville, Australia
Spawning corals broadcast their gametes typically once a year in high densities with the
resulting larvae often settling in aggregations. This provides opportunities for chimera
formation: the fusion of genetically distinct larvae into a single colony. This study
examines the extent of chimera formation under experimental conditions in juveniles of
the coral, Acropora millepora, and the frequency of chimeras in natural populations of
this species.
When larvae of Acropora millepora were settled in aquaria, more than 47% of juveniles
(n = 2168 recruits) settled in aggregations (two or more recruits in contact). Fusion within
aggregations was assumed when coral tissue was continuous within a colony and when
new polyps appeared at the contact margin. In order to assess if different genotypes
remained distinct within fused aggregations, 7 microsatellites were used to genotype subsamples
of potential genetic chimeras. Preliminary results highlight the occurrence of
genetic chimeras, indicating that Acropora millepora juveniles are able to form chimeric
entities in their early life history stages.
Although Acropora millepora juveniles form chimeras under experimental conditions,
screening the extent of genetic chimeras within adult colonies will help to understand if
chimerism also arises naturally within populations. Chimerism was assessed in two
populations (n=30 adult colonies per population) by comparing the genotypes of branches
within colonies (8 per colony) using 7 microsatellites. Chimeric colonies were found to
comprise between 3 and 6 percent of each population (or 5% overall). Thus, chimerism
occurs naturally at low frequencies in populations of Acropora millepora on the Great
Barrier Reef. As chimeras represent enhanced genetic diversity within a coral colony, the
presence of chimeras within natural populations of spawning corals on the Great Barrier
Reef may provide a selective advantage in a heterogeneous environment.
6-23
Symbiodinium – To Be An Alga Or Not, That Is The Question
Bill LEGGAT* 1,2 , David YELLOWLEES 2
1 Biochemisry and Molecular Biology, James Cook University, Townsville, Australia,
2 ARC CoE for Coral Reef Studies, James Cook University, Townsville, Australia
Symbiodinium (also called zooxanthellae) seem to conform to our traditional idea of alga
should be, they are a small single cell that photosynthesises. However the more we learn
about their genetic compliment the more unique they appear. Only recently have large
scale surveys of the dinoflagellate genome begun. This study characterises a recent large
scale sequencing effort from Symbiodinium and describes some of the unique genetic
compliment of Symbiodinium both in culture and in symbio. These unique characteristics
include a large percentage of genes which are most closely related to those found in
bacteria. These include genes that encode for a number of proteins involved in the
transport of metabolites (such as sugars), which may play a key role in the coral
symbiosis. The most abundant transcript found in the Symbiodinium transcriptome is also
of bacterial origin. Sequence analysis and antibodies indicate that it is localised to the
chloroplast where it function is unknown. This study also describes the variety of
biochemical pathways that we have characterised from Symbiodinium and how they
differ from what we might expect of a “traditional alga”, with particular emphasis on
those pathways that may be important for the coral-Symbiodinium symbiosis.
6-24
Est Screening And Multigene Analysis Of Symbiodinium Dinoflagellates: A Phylogenomic
Approach
Xavier POCHON* 1 , Ruth GATES 1
1 Hawaiian Institute of Marine Biology, Kaneohe, HI
Symbiotic dinoflagellates in the genus Symbiodinium are essential components of coral reef
ecosystems contributing to the growth, survival and success of a large array of protist and
invertebrate phyla. Phylogenies based primarily on multi-copy genes and spacers of the
ribosomal DNA operon have defined eight distinct groups within the genus Symbiodinium,
referred to as clades A through H. Each of these groups contain multiple ribotypes (ITS types)
that are often considered to represent species-level taxonomy. However, intragenomic variation
(within an individual) in the rDNA ITS markers potentially results in comparisons of
paralogues rather than orthologues and this creates a complex framework for taxonomic
interpretation. To address this issue the current work focuses on defining new, functionally
relevant and readily interpretable genes for future taxonomic studies. Interchangeable BLAST
comparisons of two Symbiodinium and six dinoflagellates EST datasets have resolved 93 new
Symbiodinium gene candidates. Eight of these genes (psbA, CoxI, CoxIII, Elongation Factor,
Calmodulin, Actin, Alpha-tubulin, and rad24) have been sequenced from Symbiodinium DNAs
representing all known clades in the genus. Five markers displayed divergence rates similar to
those found in the LSU rDNA region, and three genes (Actin, Calmodulin and rad24) harbor up
to four highly variable introns that can potentially resolve within clade Symbiodinium diversity.
The identification and phylogenetic comparison of these markers will be presented and
discussed.
6-25
The Holobiont Transcriptome Of aiptasia Pallida
Shini SUNAGAWA 1 , Monica MEDINA 1 , Virginia WEIS 2 , John PRINGLE 3 , Jodi
SCHWARZ* 4
1 School of Natural Sciences, University of California Merced, Merced, CA, 2 Department of
Zoology, Oregon State University, Corvallis, CA, 3 Department of Genetics, Stanford
University, Stanford, CA, 4 Biology Department, Vassar College, Poughkeepsie, NY
Aiptasia pallida has long served as a model for examining the physiology of coral symbiosis
and coral bleaching. To build upon the rich history of this model system, we are examining the
transcriptome of symbiotic Aiptasia, using a large insert cDNA library from which we
generated a high quality dataset of approximately 8000 ESTs. We have collaborated with our
undergraduate students to assemble and annotate these genes, and have characterized a rich set
of stress-response, developmental, signaling, and innate immune-related proteins from both the
host and the symbiont. This dataset will facilitate genomic-level examination of host-symbiont
interactions and the bleaching response. Currently, using this EST dataset, we are examining
both physiological and transcriptome-level pathways of the stress response under different
stressors, including temperature and heavy metal contamination.
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