Identifying the genetic drivers of thermal tolerance plasticity in the coral model Exaiptasia pallida

Abstract

The ancient coral-dinoflagellate partnership represents the structural and trophic foundation of the vibrant coral reef ecosystems. However, threats such as rising ocean temperatures put these ecosystems at risk. Effective conservation strategies await clear understanding of the molecular processes involved in bleaching and thermo-resilience. Recently, research efforts have been shifting towards the role of the host in coping with high temperatures, but studies are often biased on the choice of their symbiotic partners. To overcome the latter, in addition to other constraints from working directly with corals, we employed the use of genetic tools on the coral model Exaiptasia pallida. First, we elaborated an RNA-seq approach to investigate transcriptomic clues on cnidarian thermal tolerance. In this work, we exposed three genotypes of the sea anemone, namely CC7, H2 and RS, in their symbiont free state, to a heat stress treatment for 5 days. During this period, we sampled over multiple time-points to investigate the thermal tolerance response of the hosts. Transcriptomic temporal profiling analysis revealed clear differences between genotypes that reflect their distinct geographical origin. Overall, the CC7 strain exhibited by far the highest number of differentially expressed genes throughout the experiment, while the RS showed the lowest. Here, thermal stress was also linked to regulation of alternative splicing (AS). The sensitivity of AS to heat stress was revealed by the higher rate of isoform switch events during the period when temperature increased. In addition to the first experiment, we attempted to apply a in situ Hi-C protocol, for the first-time, to the sea anemone CC7. In the Hi-C chapter we report the encountered difficulties and present recommendations for future attempts.