Reef-building corals have evolved to become the foundation species of one of the most diverse and productive ecosystems of our planet. Their success is based on a symbiotic association with photosynthetic algae of the genus Symbiodinium that live inside their cells. This relationship allows corals to recycle their waste products in exchange for photosynthetically fixed carbon, thereby enabling them to thrive in the nutrient poor waters of tropical oceans.
While these fascinating organisms have endured hundreds of millions of years and survived multiple mass extinction events they are surprisingly sensitive to environmental perturbation, raising the question how such an ancient symbiotic relationship might have been formed and maintained throughout long evolutionary time scales.
What is the evolutionary history of this relationship? How do such relationships come to be and what are the mechanisms that make them evolutionary stable? To address these questions we use functional genomics and genetics approaches to unravel the molecular underpinnings of this symbiosis and its stress induced break down. We use whole genome sequencing and comparative genomic approaches to gain insight into the evolutionary history of hosts and symbionts. We analyze the genes and associated functions they have to regulate all aspects of symbiosis and ask what this can tell us about the nature of this relationship.
I believe that understanding the evolutionary history of this association is key to answering many of the pressing questions we have regarding these highly important ecosystem builders.
All these factors become even more important in the context of corals being long lived, sessile animals with long generation times. What are the mechanisms these organisms have to acclimate and adapt to these changing environmental conditions?
Epigenetic mechanisms, such as DNA methylation and histone modifications, are likely candidates to modulate and optimize the phenotypic output encoded in the genome. These mechanisms might also be involved in regulating the pronounced phenotypic plasticity these organisms display, which, for instance, allows them to change their growth form according to the prevailing conditions of light and currents. Understanding these mechanisms might provide insights into the ability of corals to mitigate the effects of climate change and prove valuable venues for coral reef restoration.
Understanding all these factors will greatly contribute to our understanding of the ecological functions of this metaorganisms and help better understand their sensitivity to changes in their environment and allow us to project how coral-reefs will respond to short- and long term environmental changes such as those projected by climate change scenarios.