Viral Interactions in Coral Holobionts

Coral holobionts comprise the cnidarian host, photosynthetic dinoflagellates, bacteria, archaea, fungi and viruses that together determine reef health and resilience. Viruses within this multipartite assemblage exhibit diverse lifestyles, from lytic agents that precipitate cell death to those integrating into host genomes as endogenous elements. They infect both coral animal tissues and resident microorganisms, modulating symbiont population dynamics, nutrient cycling and host immunity. Viral auxiliary metabolic genes can supplement host biochemistry, while viral‐mediated horizontal gene transfer may drive adaptation under environmental stress. During thermal anomalies, shifts in viral community composition and productivity often coincide with holobiont dysbiosis and bleaching, suggesting a role in both disease onset and recovery. Advances in microscopy, metagenomics and single‐cell genomics have revealed that viruses infect every compartment of the coral symbiosis, from dinoflagellate chloroplasts to coral‐associated bacteria. Understanding these interactions is crucial for predicting reef responses to climate change and for informing intervention strategies aimed at bolstering holobiont resilience.

Research from Nature Portfolio

Recent studies have unveiled how non‐retroviral RNA viruses have become embedded within the genomes of symbiotic dinoflagellates. Analyses of hundreds of cnidarian and Symbiodiniaceae metagenomes revealed widespread integration of dinoRNAV sequences adjacent to host retroelements, indicating recurrent endogenisation. These endogenous viral elements (EVEs) were absent in aposymbiotic cnidarians but abundant in dinoflagellate lineages, suggesting a long‐term association. Fragmented and variably conserved EVEs imply episodic integration events with potential impacts on host evolution, immunity and viral resistance. This work highlights a hidden dimension of coral holobiont genomics, where past viral invasions may influence current susceptibility to bleaching and disease.

Viral Interactions in Coral Holobionts publication trend

The graph below shows the total number of articles in viral interactions in coral holobionts across all publications each year (not limited to Nature Index journals).

Technical terms

Holobiont: The coral animal and its entire associated microbial community, including viruses, functioning as an ecological unit.

Symbiodiniaceae: A family of dinoflagellate microalgae that live symbiotically within coral tissues and drive reef productivity.

DinoRNAV: Positive‐sense single‐stranded RNA viruses that infect Symbiodiniaceae, influencing symbiont health and coral bleaching.

Endogenous viral elements (EVEs): Viral sequences integrated into host genomes, reflecting past infections and potential impacts on host evolution.

Auxiliary metabolic genes (AMGs): Viral‐encoded genes that supplement host metabolic pathways during infection, affecting nutrient cycling.

References

1. Filamentous virus-like particles are present in coral dinoflagellates across genera and ocean basins. The ISME Journal: Multidisciplinary Journal of Microbial Ecology (2023).
2. Viruses of a key coral symbiont exhibit temperature-driven productivity across a reefscape. ISME Communications (2023).
3. Endogenous viral elements reveal associations between a non-retroviral RNA virus and symbiotic dinoflagellate genomes. Communications Biology (2023).
4. Coral-Associated Viral Assemblages From the Central Red Sea Align With Host Species and Contribute to Holobiont Genetic Diversity. Frontiers in Microbiology (2020).