Search for: All records

Abstract The reef-building corals can thrive in nutrient-poor waters because of the mutualistic symbiosis between the animal hosts and their photosynthetic dinoflagellate endosymbionts. This symbiosis is threatened by climate change and other anthropogenic stressors, so that a deeper mechanistic understanding of its function is not only of great basic biological interest but also crucial for developing rational approaches to coral conservation. The small sea anemone Aiptasia is an attractive model system for studies of this symbiosis but has been limited to date by a lack of effective genetic methods. Here, we describe the use of a simple electroporation protocol to introduce various genetic constructs [plasmid DNAs, mRNAs, and short-hairpin (sh) RNAs] into Aiptasia zygotes. Plasmid-based expression of reporter constructs in the resulting larvae was highly mosaic. In contrast, electroporation of mRNAs into zygotes resulted in uniform expression within the larvae, and success rates were similar when single or multiple mRNAs were introduced. The shRNAs were effective in knocking down expression of both coelectroporated mRNAs and endogenous genes. In this way, we could confirm the previously reported role of BRACHYURY in cnidarian embryonic development. In addition, we could show that knockdown of an Aiptasia homologue of the lysosomal-associated membrane protein 1 interfered with larval uptake and/or retention of a symbiosis-compatible algal strain. The ability to use Aiptasia larvae for such reverse-genetic studies should greatly enhance the power of this model system and serve as a starting point for further development of genetic tools in Aiptasia and other cnidarians. 

Abstract Degradation and loss of coral reefs due to climate change and other anthropogenic stressors has fueled genomics, proteomics, and genetics research to investigate coral stress response pathways and to identify resilient species, genotypes, and populations to restore these biodiverse ecosystems. Much of the research and conservation effort has understandably focused on the most taxonomically rich regions, such as the Great Barrier Reef in Australia and the Coral Triangle in the western Pacific. These ecosystems are analogous to tropical rainforests that also house enormous biodiversity and complex biotic interactions among different trophic levels. An alternative model ecosystem for studying coral reef biology is the relatively species poor but abundant coral reefs in the Hawaiian Archipelago that exist at the northern edge of the Indo‐Pacific coral distribution. The Hawaiian Islands are the world's most isolated archipelago, geographically isolated from other Pacific reef systems. This region houses about 80 species of scleractinian corals in three dominant genera (Porites,Montipora, andPocillopora). Here we briefly review knowledge about the Hawaiian coral fauna with a focus on our model species, the rice coralMontipora capitata. We suggest that this simpler, relatively isolated reef system provides an ideal platform for advancing coral biology and conservation using multi‐omics and genetic tools. 

Coral reefs are highly diverse ecosystems of immense ecological, economic, and aesthetic importance built on the calcium-carbonate-based skeletons of stony corals. The formation of these skeletons is threatened by increasing ocean temperatures and acidification, and a deeper understanding of the molecular mechanisms involved may assist efforts to mitigate the effects of such anthropogenic stressors. In this study, we focused on the role of the predicted bicarbonate transporter SLC4γ, which was suggested in previous studies to be a product of gene duplication and to have a role in coral-skeleton formation. Our comparative-genomics study using 30 coral species and 15 outgroups indicates that SLC4γ is present throughout the stony corals, but not in their non-skeleton-forming relatives, and apparently arose by gene duplication at the onset of stony-coral evolution. Our expression studies show thatSLC4γ, but not the closely related and apparently ancestralSLC4β, is highly upregulated during coral development coincident with the onset of skeleton deposition. Moreover, we show that juvenile coral polyps carrying CRISPR/Cas9-induced mutations inSLC4γare defective in skeleton formation, with the severity of the defect in individual animals correlated with their frequencies ofSLC4γmutations. Taken together, the results suggest that the evolution of the stony corals involved the neofunctionalization of the newly arisen SLC4γ for a unique role in the provision of concentrated bicarbonate for calcium-carbonate deposition. The results also demonstrate the feasibility of reverse-genetic studies of ecologically important traits in adult corals.