The genome of the mustard hill coral, Porites astreoides

Morphological and genetic mechanisms underlying the plasticity of the coral Porites astreoides across depths in Bermuda

The widespread decline of shallow-water coral reefs has fueled interest in assessing whether mesophotic reefs can act as refugia replenishing deteriorated shallower reefs through larval exchange. Here we explore the morphological and molecular basis facilitating survival of planulae and adults of the coral Porites astreoides (Lamarck, 1816; Hexacorallia: Poritidae) along the vertical depth gradient in Bermuda. We found differences in micro-skeletal features such as bigger calyxes and coarser surface of the skeletal spines in shallow corals. Yet, tomographic reconstructions reveal an analogous mineral distribution between shallow and mesophotic adults, pointing to similar skeleton growth dynamics. Our study reveals patterns of host genetic connectivity and minimal symbiont depth-zonation across a broader depth range than previously known for this species in Bermuda. Transcriptional variations across life stages showed different regulation of metabolism and stress response functions, unraveling molecular responses to environmental conditions at different depths. Overall, these findings increase our understanding of coral acclimatory capability across broad vertical gradients, ultimately allowing better evaluation of the refugia potential of mesophotic reefs.

High-quality genome assembles from key Hawaiian coral species

BACKGROUND

Coral reefs house about 25% of marine biodiversity and are critical for the livelihood of many communities by providing food, tourism revenue, and protection from wave surge. These magnificent ecosystems are under existential threat from anthropogenic climate change. Whereas extensive ecological and physiological studies have addressed coral response to environmental stress, high-quality reference genome data are lacking for many of these species. The latter issue hinders efforts to understand the genetic basis of stress resistance and to design informed coral conservation strategies.

RESULTS

We report genome assemblies from 4 key Hawaiian coral species, Montipora capitata, Pocillopora acuta, Pocillopora meandrina, and Porites compressa. These species, or members of these genera, are distributed worldwide and therefore of broad scientific and ecological importance. For M. capitata, an initial assembly was generated from short-read Illumina and long-read PacBio data, which was then scaffolded into 14 putative chromosomes using Omni-C sequencing. For P. acuta, P. meandrina, and P. compressa, high-quality assemblies were generated using short-read Illumina and long-read PacBio data. The P. acuta assembly is from a triploid individual, making it the first reference genome of a nondiploid coral animal.

CONCLUSIONS

These assemblies are significant improvements over available data and provide invaluable resources for supporting multiomics studies into coral biology, not just in Hawai'i but also in other regions, where related species exist. The P. acuta assembly provides a platform for studying polyploidy in corals and its role in genome evolution and stress adaptation in these organisms.