Transcriptomics analysis reveals intracellular mutual regulation of coral-zooxanthella holobionts

Corals should make excellent models for cross-kingdom regulation research because of their natural animal-photobiont holobiont composition, yet a lack of studies and experimental data restricts their use. Here we integrate new full-length transcriptomes and small RNAs of four common reef-building corals with the published Symbiodinium C1 genome to gain deeper insight into mutual gene regulation in coral-zooxanthella holobionts. We show that zooxanthellae secrete miRNA to downregulate rejection from host coral cells, and that a potential correlation exists between miRNA diversity and physiological activity. Convergence of these holobionts’ biological functions in different species is also revealed, which implies the low gene impact on bottom ecological niche organisms. This work provides evidence for the early origin of cross-kingdom regulation as a mechanism of self-defense autotrophs can use against heterotrophs, sheds more light on coral-zooxanthella holobionts, and contributes valuable data for further coral research.