11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 5: Functional Biology of Corals and Coral Symbiosis: Molecular Biology, Cell Biology and Physiology
5-34
Developmental Mechanisms And The Onset Of Symbiosis in Scleractinian Coral
Embryos
Heather Q. MARLOW* 1 , Mark Q. MARTINDALE 1
1 Kewalo Marine Laboratory, University of Hawaii, Honolulu, HI
Advances in understanding symbiosis, bleaching, eco-toxicology and mineralization are
being made in adult corals, but fewer studies into the early embryonic and larval stages of
the coral life cycle have been conducted. Events critical to the survival of the coral polyp
occur in these early stages such as the development of tissue layers, acquisition of
symbionts, and formation of the nervous system. Embryonic coral development provides
the opportunity to examine ecologically relevant questions such as the onset of symbiosis
as well as questions surrounding the evolution of developmental mechanisms in corals.
Practically, embryonic material from scleractinian corals provides an excellent
opportunity to study the cell biology of the onset of symbiosis without the difficulties
associated with adult skeleton and contaminating commensal organisms. To examine the
onset of symbiosis, we have utilized cell lineage tracing experiments as well as high
resolution microscopy to examine symbiodinium uptake and localization in Fungia
scutaria and Pocillopora meandrina. Our findings suggest that an ancient anthozoan
mechanism that allows early embryos to localize yolk stores has been co-opted to
facilitate symbiodinium localization in the embryo. As a next step in more carefully
examining these events as well as those surrounding developmental mechanisms such as
neurogenesis and body axis specification we are utilizing genomic and molecular
techniques developed for the model anthozoan Nematostella vectensis. We have
cloned genes necessary for axis specification, gut formation, and neurogenesis and have
performed in situ hybridization experiments to localize these transcripts in embryonic
corals. These studies allow us to understand common themes in anthozoan development
and determine how these mechanisms affect the early life history and survival of coral
embryos.
5-35
A Computational Model For Gene Regulation Of Early Development in The Sea
Anemone nematostella Vectensis And The Coral acropora Millepora
Jaap KAANDORP* 1 , Konstantin KOZLOV 2 , Vitaly GURSKY 3 , Yves FOMEKONG
NANFACK 1 , Maksat ASHYRALIYEV 4 , Marten POSTMA 1 , Maria SAMSONOVA 2 ,
Alexander SAMSONOV 3 , David MILLER 5 , Joke BLOM 4
1 Section Computational Science, University of Amsterdam, Amsterdam, Netherlands, 2 St.
Petersburg State Polytechnical University, St Petersburg, Russian Federation,
3 Theoretical Department, The Ioffe Institute of the Russian Academy of Sciences, St
Petersburg, Russian Federation, 4 Center for Mathematics and Computer Science (CWI),
Amsterdam, Netherlands, 5 ARC Centre of Excellence for Coral Reef Studies, James
Cook University, Townsville, Queensland, Australia
Recently significant progress has been made towards understanding the genetic
regulation of early development of the cnidarians Nematostella vectensis and
Acropora millepora. Both organisms are members of the basal cnidarian Class
Anthozoa, with relatively simple body plans. Whereas in many organisms early
embryogenesis involves complex sequences of unequal cell divisions, the fact that cell
division up to gastrulation occurs equally and the expectation of relatively simple gene
regulation, make Nematostella vectensis and Acropora millepora excellent case
studies for developing a cell-based computational model of gene regulation of early
development. Despite some major morphological differences, the body of molecular data
indicates that the underlying developmental biology of both organisms is similar in many
ways, The most obvious physiological difference is that N. vectensis is a non-calcifying
sea anemone, while A. millepora secretes an extensive aragonite skeleton after
settlement. Based on in situ hybridizations available for different developmental stages of
both organisms we have developed a spatio-temporal model of gene regulation of early
embryogenesis which can be applied to both organisms (the ``AcroNema’’ model). The
model is based on a set of coupled partial differential equations. The AcroNema model is
generic for the early development of both organisms and can produce an 8-folded radial
symmetry which is characteristic for the bodyplan of Nematostella vectensis and a 6folded
symmetry which is found in the body plan in Acropora millepora. In this
generic model we propose that the gene dpp (decapentaplegic), which is responsible
for bilateral symmetrical body plans in animals, plays a fundamental role in setting up the
basic radial symmetric pattern in the developing polyp and where the initial expression
pattern of dpp determines the number of mesenteries in a developing polyp.
5-36
Circadian Clock Genes in The Coral Stylophora Pistillata, Red Sea
Eli SHEMESH* 1 , Oren LEVY 1
1 Bar Ilan University, Ramat Gan, Israel
Life on Earth has evolved under rhythmic day to night cycles of light and temperature, which
are caused by our planet's rotation. Most organisms, including prokaryotes and eukaryotes, have
evolved endogenous clocks in response to these predictable changes, allowing them to
anticipate daily and seasonal environmental cycles, and to adjust their biochemical,
physiological, and behavioral processes accordingly. The molecular mechanism of the circadian
clock contains autoregulatory feedback loops comprised of positive and negative elements that
generate 24-hour circuits. This work will present for the first time the presence of two circadian
core genes known as Clock (Clk) and Bmal, found in the coral host Stylophora pistillata, by
using degenerate primers homolog to Clock and Bmal form higher organisms. The expression
patterns of both genes was investigated under ambient light dark cycles, continuous darkness
and continuous light intensity, in order to test whether the S. pistillata clock genes act as
circadian clock genes or not. Nubbins from four mother colonies were sampled at intervals of
four hours and served for RNA extractions. The pattern of expression was tested by using
QPCR and in situ hybridizations. The results show clearly that both genes oscillate as circadian
clock genes found in higher organisms. The results presented here add important aspects into
the origin of clock genes found in the base of animalia, the cnidarians.
5-37
Physiology of Calcification and Light-Enhanced Calcification : the Scleractinian Coral
Stylophora pistillata as a Model
Sylvie TAMBUTTÉ* 1 , Eric TAMBUTTÉ 1 , Didier ZOCCOLA 1 , Aurélie MOYA 1,2 , Denis
ALLEMAND 1
1 Centre Scientifique de Monaco, Monaco, Monaco, 2 UMR 1112 INRA-UNSA, University of
Nice-Sophia-Antipolis, Nice, France
The mechanism of calcification in corals still remains enigmatic but increasing data are
available especially for the hermatypic scleractinian coral Stylophora pistillata which can be
cultivated in laboratory under controlled conditions and is thus considered as a good model to
study calcification. Since coral calcification is a case of biomineralization it involves several
components: the interface between the tissue and the skeleton, the synthesis of an organic
matrix, the transport of ions and the nucleation/growth and inhibition of crystal formation. I will
pass under review what we actually know/don’t know on the control of the organism on these
components. As an introduction, I will present an up-to-date review of the anatomy, histology
and characteristics of the interface tissue-skeleton to understand how the animal and its skeleton
are linked. I will then summarize the data obtained by physiogical and molecular approaches on
the transport of ions in Stylophora pistillata. Then I will present the current status of knowledge
on the organic fraction, from its synthesis by the tissues to its incorporation in the skeleton. I
will also highlight what are the consequences of a biological control of calcification on the
effect of environmental parameters. I will end with a presentation of the numerous
interconnected hypotheses proposed to explain light-enhanced calcification, and I will discuss
some of them in the light of the last data that we have obtained both at the physiological,
biochemical, cellular and molecular levels. I will insist on the available data but also on the
missing data necessary for a better understanding of coral calcification.
34