Dataset Information

Whole-genome transcriptome analyses of native symbionts reveal host coral genomic novelties for establishing coral-algae symbioses.

ABSTRACT: Reef-building corals and photosynthetic, endosymbiotic algae of the family Symbiodiniaceae establish mutualistic relationships that are fundamental to coral biology, enabling coral reefs to support a vast diversity of marine species. Although numerous types of Symbiodiniaceae occur in coral reef environments, Acropora corals select specific types in early life stages. In order to study molecular mechanisms of coral-algal symbioses occurring in nature, we performed whole-genome transcriptomic analyses of Acropora tenuis larvae inoculated with Symbiodinium microadriaticum strains isolated from Acropora. In order to identify genes specifically involved in symbioses with native symbionts in early life stages, we also investigated transcriptomic responses of Acropora larvae exposed to closely related, non-symbiotic, and occasionally symbiotic Symbiodinium strains. We found that the number of differentially expressed genes was largest when larvae acquired native symbionts. Repertoires of differentially expressed genes indicated that corals reduced amino acid, sugar, and lipid metabolism, such that metabolic enzymes performing these functions were derived primarily from S. microadriaticum rather than from A. tenuis. Up-regulated gene expression of transporters for those metabolites occurred only when coral larvae acquired their natural symbionts, suggesting active utilization of native symbionts by host corals. We also discovered that in Acropora, genes for sugar and amino acid transporters, prosaposin-like, and Notch ligand-like, were up-regulated only in response to native symbionts, and included tandemly duplicated genes. Gene duplications in coral genomes may have been essential to establish genomic novelties for coral-algae symbiosis.

SUBMITTER: Yoshioka Y

PROVIDER: S-EPMC7850063 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Publications

Whole-Genome Transcriptome Analyses of Native Symbionts Reveal Host Coral Genomic Novelties for Establishing Coral-Algae Symbioses.

Yoshioka Yuki Y Yamashita Hiroshi H Suzuki Go G Zayasu Yuna Y Tada Ipputa I Kanda Miyuki M Satoh Noriyuki N Shoguchi Eiichi E Shinzato Chuya C

Genome biology and evolution 20210101 1

Reef-building corals and photosynthetic, endosymbiotic algae of the family Symbiodiniaceae establish mutualistic relationships that are fundamental to coral biology, enabling coral reefs to support a vast diversity of marine species. Although numerous types of Symbiodiniaceae occur in coral reef environments, Acropora corals select specific types in early life stages. In order to study molecular mechanisms of coral-algal symbioses occurring in nature, we performed whole-genome transcriptomic ana ...[more]

PMID: 33185681

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Project description:Naval training exercises involving live ordnance can introduce munitions constituents (MCs) such as 1,3,5-trinitro-1,3,5 triazine (RDX) into the marine environment posing a potential environmental hazard to reef organisms, including corals. We developed a bioinformatic infrastructure and high-density microarray for a coral consortium and assessed the effects of RDX bioaccumulation on gene expression related to coral and endosymbiont health in the reef building coral (Acropora formosa). High-throughput sequencing and assembly of the transcriptomes for A. formosa and all eukaryotic endosymbionts yielded 189,616 unique sequences and 25,003 significant functional matches to protein-coding genes. Functional annotation and metabolic pathway associations were also developed. The bioinformatics base was transitioned to custom 15,000 probe microarrays that were used to assess RDX effects on gene expression in the A. formosa coral consortium. Coral fragments were exposed to RDX (0.5, 1, 2, 4, and 8 mg/L) for 5d in a controlled laboratory experiment. RDX readily accumulated into coral tissues; however, bioconcentration was minimal (bioconcentration factor = 1.09-1.50). RDX caused no significant changes in zooxanthellae tissue densities, however a significant (p<0.05) 40% increase in mucocytes was observed in the 8 mg/L exposure indicating a mucosal protective response to RDX exposure. Investigation of T-RFLP profiles indicated significant differences in bacterial community composition inhabiting the coral surface microlayer of Acropora sp. between control and RDX-exposed coral as among exposure concentrations. Differential expression of transcripts increased with increasing RDX concentration where 126, 195 and 272 transcripts were differentially expressed in the 0.5, 2.0 and 8 mg/L RDX treatments, respectively. The commonality in differentially expressed transcripts (DET) among exposure concentrations ranged from 9.9 to 29.0% where the lowest commonality was observed between the most disparate RDX exposure concentrations. Increasing RDX concentrations caused an increasing proportion of the number of transcripts differentially expressed in symbionts relative to corals. Further, a trend toward decreased transcript expression in symbionts in response to increasing RDX concentration was observed where 20.0% of differentially expressed transcripts had decreased expression at the 0.5 mg/L concentration, whereas 80.4% had decreased expression at the 8 mg/L concentration. Investigation of KEGG orthology for DET indicated potential impacts of RDX on a variety of molecular pathways, predominantly in endosymbionts compared to the coral host. Prominent effects of RDX exposure on pathways included enrichment of DET involved in carbohydrate metabolism, amino acid metabolism, energy metabolism, lipid metabolism, metabolism of cofactors and vitamins, environmental information processing and cellular processes. Fragments of the living branched coral Acropora formosa were obtained from Oceans, Reefs and Aquaria (http://www.orafarm.com). Ten gallon aquaria were used to expose 5 coral fragments to control or RDX exposure conditions (0.49, 0.93, 1.77, 3.67 and 7.18 mg/L, measured concentrations). The microarray hybridization experiment included 3 biological replicates for the 0.5, 2, and 8 mg/L RDX conditions and 4 biological replicates for the control.

Project description:Benthic algae are associated with coral death in the form of stress and disease. It's been proposed that they release exudates, which facilitate invasion of potentially pathogenic microbes at the coral-algal interface, resulting in coral disease. However, the original source of these pathogens remains unknown. This study examined the ability of benthic algae to act as reservoirs of coral pathogens by characterizing surface associated microbes associated with major Caribbean and Indo-Pacific algal species/types and by comparing them to potential pathogens of two dominant coral diseases: White Syndrome (WS) in the Indo-Pacific and Yellow Band Disease (YBD) in the Caribbean. Coral and algal sampling was conducted simultaneously at the same sites to avoid spatial effects. Potential pathogens were defined as those absent or rare in healthy corals, increasing in abundance in healthy tissues adjacent to a disease lesion, and dominant in disease lesions. Potentially pathogenic bacteria were detected in both WS and YBD and were also present within the majority of algal species/types (54 and 100% for WS and YBD respectively). Pathogenic ciliates were associated only with WS and not YBD lesions and these were also present in 36% of the Indo-Pacific algal species. Although potential pathogens were associated with many algal species, their presence was inconsistent among replicate algal samples and detection rates were relatively low, suggestive of low density and occurrence. At the community level, coral-associated microbes irrespective of the health of their host differed from algal-associated microbes, supporting that algae and corals have distinctive microbial communities associated with their tissue. We conclude that benthic algae are common reservoirs for a variety of different potential coral pathogens. However, algal-associated microbes alone are unlikely to cause coral death. Initial damage or stress to the coral via other competitive mechanisms is most likely a prerequisite to potential transmission of these pathogens.

Dataset Information

Whole-genome transcriptome analyses of native symbionts reveal host coral genomic novelties for establishing coral-algae symbioses.

Publications

Whole-Genome Transcriptome Analyses of Native Symbionts Reveal Host Coral Genomic Novelties for Establishing Coral-Algae Symbioses.

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