11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 5: Functional Biology of Corals and Coral Symbiosis: Molecular Biology, Cell Biology and Physiology
5-14
Directed Pocilloporin Expression And Amino Acid Translocation in Response To
Physical Injury in Scleractinian Coral Colonies
Jeffry DECKENBACK* 1 , Sophie DOVE 1
1 Centre for Marine Studies, University of Queensland, St Lucia, Australia
This research focused upon the potential for coral colonies to collect dissolved organic
materials from external sources in response to physical injury and to translocate these
materials in a specific manner in order to aide in regrowth and/or increased pocilloporin
production. Within healthy coral tissues, myriad biochemical pathways exist both to
harvest solar energy and prevent photo-inhibition by blocking or channelling excess
energy that would otherwise damage the photosystems. Calcium carbonate skeleton
exposed by injury may increase the path length of incident visible wavelength photons,
reflecting them into the already disturbed tissues that border the sites of injury. By
pooling and reallocating biochemical resources as appropriate, Scleractinian coral
colonies can decrease the cost of regrowth to polyps at the site of injury by spreading this
cost throughout the whole colony. Observations identified bands of bright pigment,
likely a pocilloporin variant, surround sites of injury within 48 hours of initial injury.
14C-labelled amino acids were injected into selected artificially injured colonies of tan
morph Montipora sp. and allowed to incubate. Upon appearance of pigment bands at
injury sites, samples were collected to quantify host pigment content, mRNA signal
expression, amino acid content, and total radioactivity. Injured corals expressed a strong
response to physical injury, collecting available amino acids and allocating these within
the colony as required to start the regrowth processes while also up-regulating
pocilloporin mRNA signal expression within polyps closest to the site of injury. At the
site of injury, regrowth was observed within two days, creating a region distinct from
both the healthy tissue and exposed skeleton. Within this region, chlorophyll-specific
absorbance was significantly lower than within healthy tissues, but pocilloporin-specific
absorbance was unchanged relative to healthy tissues. In all, the coral colonies
demonstrated very active and directed healing and recovery responses in response to
physical injuries.
5-15
The Effect Of Fluctuating Light On symbiodinium Photosynthetic Gene
Expression
Lynda BOLDT* 1 , David YELLOWLEES 2 , Sophie DOVE 3 , Bill LEGGAT 2
1 School of Pharmacy and Molecular Sciences, James Cook University, Townsville, QLD,
Australia, 2 School of Pharmacy and Molecular Sciences, James Cook University,
Townsville, Australia, 3 Centre for Marine Studies, University of Queensland, Brisbane,
Australia
This study examined the membrane bound light harvesting proteins of Symbiodinium, an
endosymbiotic dinoflagellate of reef building corals as well as other marine invertebrates.
We investigated whether genes involved in photosynthesis are differentially expressed on
a diurnal basis and if known physiological responses can be linked with differential gene
expression. Putative membrane bound light harvesting proteins of Symbiodinium isolated
from Acropora aspera collected from the reef flat surrounding Heron Island were
characterized with several indicating homology with red algae while the major homology
was with other dinoflagellate light harvesting proteins. To further elucidate the
relationship between light and Symbiodinium photosynthesis, Symbiodinium isolated
from Acropora formosa collected from Orpheus Island, part of the Palm Island group on
The Great Barrier Reef, were analysed and photosynthetic gene expression compared
with samples exposed to no light over a 24 hour period. While there were no significant
physiological differences or variation in photosystem II functionality between coral
branches exposed to no light and those exposed to diurnal light fluctuations, the response
of various genes involved in photosynthetic processes did vary diurnally. This work is
the first to examine the putative membrane bound light harvesting proteins of
Symbiodinium and confirm that photosynthetic genes of Symbiodinium isolated from a
reef building coral are differentially expressed on a diurnal basis and that the removal of
light results in the down regulation of key light dependent photosynthetic genes.
5-16
Light Energy Transformation Processes By Fluorescent Pigments Of Corals
Anya SALIH* 1 , Yuri ZAVOROTNY 2
1 Confocal Bio-Imaging Facility, University of Western Sydney, Penrith, Australia, 2 Advanced
Laser Technologies Department, Institute of Laser and Information Technologies RAS,
Moscow, Russian Federation
Tissues of reef building corals are pigmented by multi-colored and fluorescent proteins
belonging to a family of GFPs (Green Fluorescent Proteins). Experimental evidence indicates
that one of the major biological functions of these pigments is in light regulation and
photoprotection by light absorption, scattering and energy transformation via fluorescence. Here
we examine the different modes of energy transformation by GFP-type proteins in tissues of
shaded, light-acclimated and bleached Great Barrier Reef (Australia) corals using steady state
fluorescence spectroscopy and Fluorescence Life-Time Imaging (FLIM) confocal microscopy.
We show that corals can dynamically regulate energy transformation properties of their tissues
in response to light as it passes through pigments. In low light corals, Förster resonance energy
transfer (FRET) capacity of tissues was reduced compared to high light corals and both nonradiative
FRET and radiative energy channelling capacity were increased in the latter. Cellular
fluorescence lifetimes were highest in several acroporiid bleached species examined, indicating
that GFP-type proteins increased cellular capacity to dissipate excessive incident light. Since
light energy transfer processes among chlorophyll molecules determine the photosynthetic
efficiency of coral’s symbiotic microalgae, FLIM of symbionts in live tissues was also used to
provide a rapid and efficient means to access their health. At high irradiances, chlorophyll
lifetimes of GFP-pigmented tissues were shorter than of less pigmented ones, indicative of less
photo-stressed microalgae. Our study showed that confocal micro-spectral imaging in
combination with FLIM provides a rapid and an accurate method to visualise and analyse
cellular and optical properties of the coral host and to quantitatively determine the
photosynthetic capacity of the symbionts. The study provides important information about the
physiological responses of the host to light, the cellular mechanisms it uses to counteract photostress
and to reduce the susceptibility to bleaching.
5-17
Roles And Origins Of Superoxide Dismutases in A Symbiotic Cnidarian
Paola FURLA* 1 , Sophie RICHIER 2 , Pierre-Laurent MERLE 1 , Ginette GARELLO 1 , Amandine
PLANTIVAUX 3 , Didier FORCIOLI 1 , Denis ALLEMAND 4
1 EA ECOMERS, Nice-Sophia Antipolis University, Nice cedex 02, France, 2 UMR 7093,
Villefranche-sur-mer oceanological observatory, Villefranche-sur-Mer Cedex, France, 3 NUI
Galway, Galway, Ireland, 4 Scientific Center of Monaco, Monaco, Monaco
Cnidarians living in symbiosis with photosynthetic dinoflagellates daily experience hyperoxia
state due to the photosynthetic activity of the symbiont. Studies on the symbiotic sea anemone,
Anemonia viridis, showed an increase of three-fold normoxic value within the coelenteric
cavity after 20 minutes of light exposure. However, no accompanying oxidative damage was
observed suggesting the presence of efficient antioxidant defenses. Among them, superoxide
dismutases (SOD) constitute the first line of antioxidant defense. A detailed analysis of this
enzyme family in both host tissues and symbionts showed several particularities in ‘symbiotic
cnidarians’ such as high isoform diversity and presence of extracellular SOD and common
isoforms between the two partners. Eight SOD isoforms have been identified belonging to four
SOD classes : 4 Manganese SOD (MnSOD), 1 intracellular copper-zinc SOD (CuZnSOD), 1
extracellular copper-zinc SOD (ECSOD) and 2 iron SOD (FeSOD). Although both intracellular
and extracellular CuZnSOD were localized exclusively to the cnidarian host tissues MnSOD
and FeSOD isoforms are shared between the two partners. Investigation of the genetic origin of
these shared SODs unveiled high degree of co-evolution between the two organisms inferring
mechanism of protein translocation and events of horizontal gene transfert.
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