Conclusions and future studies
This study showed that maternal effects manifested as gene expression differences in interspecific hybrids of the coral A.tenuis and A. loripes . We also showed that maternal effects can persist to at least seven months of age in coral and were likely responsible for the phenotypes of F1 hybrids. However, the pathways and mechanisms responsible for the phenotypic differences were unknown and exposure to elevated temperature andp CO2 conditions did not result in differential coral gene expression. Although the composition of bacterial and microalgal endosymbiont communities of these corals was similar under ambient and elevated conditions and between hybrids and purebreds, these microbes may have expressed different genes and contributed to holobiont phenotypic differences. Future studies will benefit from examining the gene expression of these microbial communities alongside the host. Other less studied members of the coral holobiont, such as viruses and fungi (that were not examined), may also have contributed to coral survival and size differences between offspring groups and treatment conditions. Further, post-transcriptional and epigenetic regulation (e.g., DNA methylation) may have varied between treatments and hybrid and purebreds and may have resulted in phenotypic differences (Dimond et al., 2017). Future studies should consider adopting a multi-omics approach and assessing other members of the coral-associated microbiome to explore other mechanisms that underpin the phenotype of the coral holobiont.
Acknowledgements. We thank P. Buerger, C. Kenkel and P. Laffy for fruitful discussions, and support from the National Sea Simulator team of AIMS. This research was funded by the Paul G. Allen Family Foundation and the Australian Institute of Marine Science (AIMS). WYC acknowledges the University of Melbourne International Research Scholarship and Fee Remission Scholarship. MvO acknowledges Australian Research Council Laureate Fellowship FL180100036.
Author’s ontribution. W.Y.C., M.J.H.O., L.P. and A.H. designed the study. W.Y.C. and
L.P. conducted the experiment. L.P. carried out the laboratory work. J.C., W.Y.C. and A.H. undertook bioinformatic and statistical analyses. W.Y.C. and M.J.H.O. wrote much of the manuscript and all authors contributed to the final edited version of the manuscript.
Data Availability Statement
Raw sequences are available in GenBank (SRR12695232 to SRR12695253, project accession no.: PRJNA665083) and the R scripts for statistical analyses are available as Appendix S1.