Shedding light on corals: How DNA damage repair, the circadian clock and cryptochromes shape the response of Anthozoa to sunlight

• Applicants: Professor Dr. Nicholas S. Foulkes; Professorin Dr. Annika Guse
• Subject Area: Animal Physiology and Biochemistry ; Evolutionary Cell and Developmental Biology (Zoology) ; Cell Biology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 508441598

Coral reefs are the most biodiverse marine ecosystems on this planet. They thrive in relatively harsh habitats, which are characterized by low levels of nutrients and high levels of sunlight. To overcome these challenges, reef-building corals (class Anthozoa, phylum Cnidaria) exploit sunlight and form a stable symbiosis with photosynthetic, single-celled dinoflagellate algae of the genus Symbiodiniacae. These algae transfer essential nutrients to their coral host. However, corals are sessile animals and are therefore inevitably exposed to sustained high levels of ultraviolet (UV) radiation, the primary cause of DNA damage. To date it is unclear how corals balance the essential harvest of sunlight to promote symbiont photosynthesis while avoiding excessive DNA damage and thus genomic instability. To address this, we will use the symbiotic sea anemone Aiptasia as a model, in combination with comparative fieldwork to better understand how corals adapt to the various effects of sunlight in their environments. What are the molecular adaptations to withstand high levels of UV radiation? How are they interconnected with DNA damage repair mechanisms and the circadian clock? To what extend are these adaptations shaped by the coral-dinoflagellate symbiosis? We will use bioinformatics to identify the DNA damage repair “toolkit” in Anthozoa. Next, we will relate the dynamic changes in gene expression of the key components to distinct lighting regimes and to levels of DNA damage in Aiptasia and corals. At the mechanistic level, we will specifically test the hypothesis that Anthozoa evolved an atypical, photo-reactive DNA repair enzyme of the cryptochrome/photolyase (CRY/PL) family of enzymes called AnthoCRY to adapt to their light-dominated habitats. We will compare AnthoCRYs with other members of the diverse group of photo-reactive CRY/PLs in cell-based assays, structure-function analyses in vitro and functional experiments in vivo. By this approach we will reveal the mechanisms whereby corals adapt to high levels of UV exposure and thus transform a challenging environment into one of the most productive marine ecosystems on our planet.

• DFG Programme: Research Grants