11th ICRS Abstract book - Nova Southeastern University

Poster Mini-Symposium 5: Functional Biology of Corals and Coral Symbiosis: Molecular Biology, Cell Biology and Physiology
5.141
Effect Of Irradiance And Increased Temperature On Differential Gene Expression
In Dinoflagellate
Nedeljka ROSIC 1 , Mauricio RODRIGUEZ-LANETTY 1 , William LEGGAT 1 , Ove
HOEGH-GULDBERG* 1
1 The University of Queensland, Brisbane, Australia
Using microarray technology, with over 3000 ESTs, we assessed gene expression profiles
in symbiotic dinoflagellate from culture after exposure to elevated temperature and light
level. Cultures of the coral symbionts, Symbiodinium sp. from clade C1 have been
exposed to elevated temperatures (29ºC and 32ºC) under high (100 µmole quantum/m2/s
Photosynthetic Active Radiation) and low (15 µmole quantum/m2/s) light level. As a
result we discovered some interesting genes involved in stress respond in dinoflagellate.
Heat shock proteins such as DnaJ molecular chaperone (HSP 40), which is involved in
protein translation and folding, then serine/threonine-protein kinase have been up
regulated with increased temperature. Light level effected expression of various genes
such as actin, ammonium and nitrate transporters. Also, a list of potential house keeping
genes has been established from this sequence as a good basis for further gene expression
studies in symbiotic dinoflagellate. These preliminary microarray data should provide
more information and highlight future directions towards better understanding of the
process involved in the breakdown of coral-algal symbiosis.
5.142
Genetic Diversity Of The Zooxanthellae Symbionts Of Corals From Reunion Island
Fabien GUÉRIN* 1 , Laury DIJOUX 2 , Xavier HOENNER 2,3 , Vianney DENIS 2 , Henrich
BRUGGEMANN 2 , Mireille GUILLAUME 2,4
1 UMR PVBMT, Université de la Réunion, Saint Denis, Reunion, 2 ECOMAR, Université
de la Réunion, Saint Denis, Reunion, 3 Te mana o te moana, Moorea, French Polynesia,
4 Milieux et Peuplements Aquatiques, UMR 5178 CNRS-UPMC-MNHN, Muséum
National d'Histoire Naturelle, Paris, France
In the Western Indian Ocean extinction of coral reefs in response to global change has
been predicted within the next 50 years. Reefs at Reunion, a high island in an exposed
oceanic setting at high latitude (21° S), were hitherto little affected by the strong 1997-98
ENSO event. Although recurrent bleaching events are occurring since, they probably still
contain ‘naïve’ coral communities with original species composition, locally dominated
by Acropora. The future of these communities depends of the capacity of corals to adapt
or acclimatize to climate change. Zooxanthellae clade D has been shown to impart greater
tolerance to high temperatures.
This is the first study of genetic diversity and distribution of zooxanthellae at Reunion
Island, aiming to better understand the potential of its coral reefs to cope with the SST
increase. From January to April 2007 a minimum of ten replicate coral colonies of some
abundant species was sampled on both top and side parts from each colony. After
holobiont DNA extraction, samples were analysed by PCR-RFLP (Polymerase Chain
Reaction – Restriction Fragment Length Polymorphism) on small and long subunit
ribosomal nRNA of symbionts using TaqI and HhaI as restriction enzymes.
Zooxanthellae RFLPs were classified in clades according to Rowan and Powers (1991)
and Baker et al. (1997). Clade C was dominant in Acropora austera, A. gemmifera, A.
muricata, Porites lutea and P. (Synarea) rus. Branch tips in three colonies of A.
gemmifera were bicladic, harbouring clade C and A. Clade D was also found in
Montipora circumvallata, a species characteristic of degraded coral reef flat communities.
So far, these results suggest a higher potential for resilience to SST increase in
A.gemmifera and M. circumvallata than in other coral species.
5.143
Seasonal Acclimation in Photosynthetic Efficiency Of Coral Holobiont Photosynthesis
Angela LAWTON* 1
1 Centre for Marine Studies, University of Queensland, St Lucia, Australia
Faced with current predictions of 2 C warming by 2050, many people hope that corals will be
able to acclimate to the increased temperature, but little is known about the acclimatory ability
of the coral holobiont.
In order to determine if the coral holobiont is able to acclimate its photosystems and
metabolism to seasonally varying environmental conditions, PI curves from Pavona decussata
and Stylophora pistallata were measured at the end of summer (February) and the end of winter
(August) for 3 years using fast-responding microsensors and the light-dark shift method of
Revsbech (1989). The gross and net photosynthetic rates of nubbins of Pavona decussata and
Stylophora pistilata were measured over a range of temperatures during both the summer and
winter to determine if the effect of temperature of the gross and net photosynthetic rates was
different from summer to winter.
It was determined that corals are able to adjust their metabolisms in order to maximize the
amount of photosynthesis occurring in both the summer and winter. Also, the tolerance to
extreme temperature was reduced in the winter. These results indicate that the coral holobiont
does use acclimatory mechanisms to maximize the amount of C gained seasonally. The
mechanisms of seasonal acclimation may be able to be used to acclimate to warmer conditions,
but there is no indication what the maximum range of acclimation is.
5.144
Survival At The Surface: Enhanced Photoprotection Pathways in Shallow Water
symbiodinium
Jennifer McCabe REYNOLDS* 1 , Brigitte BRUNS 2 , William FITT 1 , Gregory SCHMIDT 2
1 Odum School of Ecology, University of Georgia, Athens, GA, 2 Department of Plant Biology,
University of Georgia, Athens, GA
Photoprotections are necessary for the survival of the coral-dinoflagellate symbiosis. However,
not all symbiont phylotypes display the same sensitivity to the enhancement of photosynthetic
loss at high light and temperatures. We have found that members of different clades in the
genus Symbiodinium exhibit distinct physiological responses as measured by a novel serial
irradiation pulse (SIP) PAM fluorometry method. We monitored fluorescence patterns
indicative of photoprotections using the SIP method from March 2006 to August 2007 in three
coral species in symbiosis with different Symbiodinium clades to determine seasonal changes in
photosynthetic physiology as ocean temperatures fluctuated naturally and light intensity was
increased artificially.
The synergism of sustained high light and increased temperature underlies damage to the coraldinoflagellate
symbiosis by causing photosynthetic loss in Symbiodinium cells. Unlike Clades B
and C, Clade A Symbiodinium, in culture and in hospice, show enhanced capabilities for
alternative photosynthetic electron transport pathways including cyclic and/or chlororespiratory
electron transport. Clade A Symbiodinium also undergo pronounced light-induced dissociation
of antennae complexes from Photosystem II reaction centers as a major component of nonphotochemical
quenching. Cnidarians harboring Clade A Symbiodinium exhibit sustained cyclic
activities coincidental with diminished bleaching during periods of elevated temperature and
high light.
Supported by NSF grant OCE-0137007 to Fitt and Schmidt and a NOAA Dr. Nancy Foster
Scholarship to J.C.M. Reynolds.
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