Project description:This experiment assessed the natural gene expression variation present between colonies of the Indo-Pacific reef-building coral Acropora millepora, and additionally explored whether gene expression differed between two different intron haplotypes according to intron 4-500 in a carbonic anhydrase homolog. This study found no correspondence between host genotype and transcriptional state, but found significant intercolony variation, detecting 488 representing unique genes or 17% of the total genes analyzed. Such transcriptomic variation could be the basis upon which natural selection can act. Underlying variation could potentially allow reef corals to respond to different environments. Whether this source of variation and the genetic responses of corals and its symbionts will allow coral reefs to cope to the rapid pace of global change remains unknown.
Project description:This experiment assessed the natural gene expression variation present between colonies of the Indo-Pacific reef-building coral Acropora millepora, and additionally explored whether gene expression differed between two different intron haplotypes according to intron 4-500 in a carbonic anhydrase homolog. This study found no correspondence between host genotype and transcriptional state, but found significant intercolony variation, detecting 488 representing unique genes or 17% of the total genes analyzed. Such transcriptomic variation could be the basis upon which natural selection can act. Underlying variation could potentially allow reef corals to respond to different environments. Whether this source of variation and the genetic responses of corals and its symbionts will allow coral reefs to cope to the rapid pace of global change remains unknown. A. millepora colonies were brought to a common garden in the reef lagoon, i.e. under the same environmental conditions. This common garden combined with acclimatization removes environmental effects on the physiology of the coral colonies. For the comparison of the two intron haplotypes, we applied a multiple dye-swap microarray design for the two groups of coral colonies (N=3 per group) defined based on the two genotypes resolved with the use of intron 4-500 (Fig. 1). To also examine the intra-haplotype variation we added a loop design nested to the above multiple dye-swap design, where three samples per colony were included. Colonies 1, 2, and 3 are of intron 4-500 haplotype 1; colonies 4, 5, and 6 are haplotype 2.
Project description:For sessile organisms at high risk from climate change, phenotypic plasticity can be critical to rapid acclimation. Epigenetic markers like DNA methylation are hypothesized as mediators of plasticity; methylation is associated with the regulation of gene expression, can change in response to ecological cues, and is a proposed basis for the inheritance of acquired traits. Within reef-building corals, gene body methylation can change in response to ecological stressors. If coral DNA methylation is transmissible across generations, this could potentially facilitate rapid acclimation to environmental change. We investigated methylation heritability in Acropora, a stony reef-building coral. Two A. millepora and two A. selago adults were crossed, producing eight offspring crosses (four hybrid, two of each species). We used whole-genome bisulfite sequencing to identify methylated loci and allele-specific alignments to quantify per-locus inheritance. If methylation is heritable, differential methylation (DM) between the parents should equal DM between paired offspring alleles at a given locus. We found a mixture of heritable and non-heritable loci, with heritable portions ranging from 44% to 90% among crosses. Gene body methylation was more heritable than intergenic methylation, and most loci had a consistent degree of heritability between crosses (i.e., the deviation between parental and offspring DM were of similar magnitude and direction). Our results provide evidence that coral methylation can be inherited but that heritability is heterogenous throughout the genome. Future investigations into this heterogeneity and its phenotypic implications will be important to understanding the potential capability of intergenerational environmental acclimation in reef building corals."
Project description:Two known settlement/metamorphosis inducing stimuli (crustose coralline algae, and ethanolic extract of crustose coralline algae) and one stimulus which just induces metamorphosis (LWamide) were used to stimulate competent planula larvae of the coral Acropora millepora. Samples were taken 0.5h, 4h and 12h post induction isolate the genes controlling settlement and metamorphosis in this coral.
Project description:Purpose: Corals are major sources of dimethylsulphoniopropionate (DMSP), a compound that plays a central role in the global sulphur cycle. While DMSP biosynthesis pathways have been investigated in plants and algae, the molecular basis for its production by corals is unknown. Given its potential role as an osmolyte, the effect of salinity stress on levels of DMSP was investigated in both adults and juveniles (lacking photosynthetic symbionts) of the coral Acropora millepora. This study used transcriptomic data to analyse the effects of salinity over the coral A. millepora and to identify coral genes likely to be involved in DMSP biosynthesis. Methods: Adults coral transcriptomic libraries were constructed from samples exposed during 1 and 24 hours of salinity treatment (25 PSU) and control (35 PSU) conditions (n=5 per condition). Juveniles coral transcriptomic libraries were constructed from samples exposed to 24 and 48 hours of salinity treatment (28 PSU) and control (35 PSU) conditions (n=6 per condition). All libraries were sequenced by 100 bp paired-end in a HiSeq 2000. Reads were mapped onto the Acropora millepora genome using TopHat2 to produce a count data gene expression matrix for subsequent gene expression analysis using DESeq2 package. Results: In adult coral samples, 5.5 - 10.2 million RNAseq reads were obtained for each treatment sampling time while 3.4 - 8.8 million reads were obtained for each juvenile coral sample. The count matrix of the 26,622 A. millepora gene predictions were generated using htseq-count workflow. BlastP analysis of the A. millepora gene predictions led to the identification of coral members of gene families implicated in DMSP biosynthesis in other organisms, while RNA-seq data was used to identify the differentially expressed ones in response to hyposaline stress and on this basis were considered to be candidates for roles in DMSP biosynthesis in corals. Conclusions: Hyposaline stress increased DMSP production in both adults and aposymbiotic juvenile corals, and transcriptomic analyses highlighted the potential involvement of specific candidate genes in the production of DMSP via an alga-like pathway. The biochemistry of DMSP production is not well established for any eukaryotic system and, as the first animals in which it has been demonstrated, this is particularly true in the case of corals. Our RNA-seq results enabled the identification of candidates for roles in DMSP biosynthesis in corals but, given its critical roles in diverse biological processes, a thorough investigation of the molecular mechanisms leading to its production by corals is required.
Project description:The metabolic bases of the interaction between the coral Acropora millepora and its dinoflagellate symbiont were investigated by comparing gene expression levels under light and dark conditions at the whole transcriptome level. Among the differentially expressed genes identified, a suite of genes involved in cholesterol transport was found to be up-regulated under light conditions, confirming the significance of this compound in the coral symbiosis. Although ion transporters likely to have roles in calcification were not differentially expressed in this study, expression levels of many genes associated with skeletal organic matrix composition and organization were higher in light conditions. This implies that the rate of organic matrix synthesis is one factor limiting calcification at night. Thus, LEC during the day is likely to be a consequence of increases in both matrix synthesis and the supply of precursor molecules as a result of photosynthetic activity. Branch tips from three adult colonies of Acropora millepora were sampled at midday and midnight
Project description:This studies investigates the acute response of the coral Acropora millepora to two immunogenes: MDP (bacterial mimic) and pIC (viral mimic). Three members of the GiMAP familly were found to respond strongly to MDP treatment, showing analalogy to the immune response in vertebrates and plants.