The symbiotic relationship between cnidarians and their photosynthetic dinoflagellate
symbionts underpins the success of coral reef communities in oligotrophic, tropical seas.
Despite several decades of study, the cellular and molecular mechanisms that regulate the
symbiotic relationship between the dinoflagellate algae and the coral hosts are still not
clear. One of the hypotheses on the metabolic interactions between the host and the
symbiont suggests that ammonium assimilation by the host can be the underlying
mechanism of this endosymbiosis regulation. An essential intermediate of the ammonium
assimilation pathway is glutamate, which is also known for its glutamatergic signaling
function. Interestingly, recent transcriptomic level and DNA methylation studies on sea
anemone Aiptasia showed differences in metabotropic glutamate signaling components
when comparing symbiotic and non-symbiotic animals. The changes in this process on
transcriptional and epigenetic levels indicate the importance of glutamate signaling in
regard to cnidarian symbiosis. In this study, I tested glutamatergic signaling effect on
symbiosis in sea anemone Aiptasia using a broad-spectrum glutamate receptor inhibitor 7-
CKA and glutamate. Significantly decreased cell density was observed in animals with
inhibitor treatment suggesting a possible correlation between glutamate signaling and the
establishment or maintenance of symbiosis. Using RNA-Seq, I was able to obtain
transcriptional profiles of the animals under inhibitor and glutamate treatment. Differential
gene expression and gene ontology analyses indicated changes in amino acid metabolism,
lipid metabolism and such signaling pathways as MAPK, NF-kappa B and phospholipase
C. Although amino acid and lipid metabolism could be a result of the reduced symbiotic
state of inhibitor treated Aiptasia, the signaling pathways which are related to apoptosis
and immune response provide an exciting venue for direct regulatory interaction between
symbiosis and glutamatergic signaling. However, as these signaling pathways mainly act
via signal transduction through protein phosphorylation, further studies looking at changes
on a post-translational level might provide further insight into the mechanisms underlying
the observed phenotype.
| Date of Award | Apr 2020 |
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| Original language | English (US) |
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| Awarding Institution | - Biological, Environmental Sciences and Engineering
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| Supervisor | Manuel Aranda (Supervisor) |
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- Aiptasia
- symbiosis
- glutamate
- signaling
- RNA-Seq