The enormous importance of coral reefs is widely recognized, as is the
unfortunate fact that corals throughout the world are greatly threatened by a variety of
anthropogenic stresses

Pringle, John

KAUST Repository (King Abdullah University of Science and Technology)

Red Sea Research Center SymposiumSession Topic: Coral Reef Ecology and GenomicsSession Leaders: Prof. Michael Berumen & Prof. Christian VoolstraJohn Pringle, Stanford University, USATitle: A Model System for Studies of Dinoflagellate-Cnidarian SymbiosisAbstract:  The enormous importance of  coral  reefs  is  widely  recognized,  as  is  the unfortunate fact that corals throughout the world are greatly threatened by a variety of  anthropogenic stresses.  These stresses can lead to a loss of the intracellular algal  symbionts whose photosynthesis provides the bulk of the corals' nutrition, resulting in subsequent coral death.  Thus, there has been much recent attention to corals and their problems from marine and conservation biologists. Missing, however, has been a commensurate attention to the molecular and cellular mechanisms that underlie coral growth  and  the  interactions  between  the  animal  hosts  and  their  symbiotic  algae (dinoflagellate genus Symbiodinium).  The lack of such basic information is a serious impediment to understanding and addressing the ecological and conservation issues.Major obstacles to improved understanding of basic coral molecular and cell biology have been the intrinsic difficulties of studies under field conditions and the intractability for laboratory investigation of organisms that form large colonies (although individual polyps are typically small) and are encased in rock, slow-growing, finicky about their environment,  genetically  heterogeneous  (to  an  unknown  extent),  and  incapable  of surviving long without their symbionts.  Most of the enormous progress of the past 50 years in elucidating the basic mechanisms of eukaryotic molecular and cell biology has come from intensive studies of a small number of "model organisms" that were chosen not  for  any  particular  ecological  or  economic  importance  but  because  they  have properties that facilitate laboratory investigation.  It seems certain that this will also be true for corals, Symbiodinium, and their interactions.The small sea anemone Aiptasia sp. offers an outstanding opportunity to develop the needed model system.  Aiptasia contains Symbiodinium types similar or identical to those  found  in  corals,  has  a  convenient  range  of  polyp  sizes  (~1.5-40  mm),  is noncalcifying (and thus easily observed microscopically, squashed, or homogenized), grows  rapidly  (mass-doubling  times  of  1-2  weeks),  is  tolerant  of  widely  varying environmental conditions, reproduces asexually by "pedal laceration", and can survive indefinitely in the absence of Symbiodinium.  We are engaged in a systematic effort to  develop this model system.  For example, we have generated large clonal populations of  Aiptasia  and  clonal,  axenic  strains  of  both  compatible  and  incompatible Symbiodinium; improved methods for precise counting of algal numbers; completed a transcriptome assembly for aposymbiotic animals and begun such analyses for both cultured Symbiodinium and symbiotic Aiptasia; begun analysis of the Aiptasia genome sequence; and taken a major step toward developing Aiptasia genetics by identifying conditions that induce spawning and larva production in the laboratory.I  will  summarize both these efforts  in  model-system development and some of the specific biological questions that we are investigating using this system.  

A Model System for Studies of Dinoflagellate-Cnidarian Symbiosis

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