RT Journal Article SR Electronic T1 Transcriptomic insights into the establishment of coral-algal symbioses from the symbiont perspective JF bioRxiv FD Cold Spring Harbor Laboratory SP 652131 DO 10.1101/652131 A1 Amin R Mohamed A1 Natalia Andrade A1 Aurelie Moya A1 Cheong Xin Chan A1 Andrew P. Negri A1 David G. Bourne A1 Eldon E Ball A1 David J Miller YR 2019 UL http://biorxiv.org/content/early/2019/05/31/652131.abstract AB Despite the ecological significance of the mutualistic relationship between Symbiodiniaceae and reef-building corals, the molecular machinery underpinning the establishment of this relationship is not well understood. This is especially true of the symbiont side, as previous attempts to understand the interaction between coral larvae and Symbiodiniaceae have focused nearly exclusively on the host. In the current study, Acropora tenuis planula larvae were exposed to a compatible strain of Symbiodiniaceae (Cladocopium) and the transcriptomic landscape of the symbiont profiled at 3, 12, 48 and 72 h post-exposure using RNA-Seq. The transcriptomic response of Cladocopium to the symbiotic state was complex, the most obvious feature being an extensive and generalised downregulation of gene expression. Included in this “symbiosis-derived transcriptional repression” were a range of stress response and immune-related genes. In contrast, genes implicated in metabolism were upregulated in the symbiotic state. Consistent with previous ecological studies, this transcriptomic response of Cladocopium implied that active translocation of metabolites to the host occurred, and thus that the mutualistic relationship can be established at the larval stage. This study provides novel insights into the transcriptomic remodelling that occurs in Symbiodiniaceae, with important implications for understanding the establishment of symbiosis between corals and their dinoflagellate partners.