Project description:The Amazon molly is a unique clonal fish species that originated from an interspecies hybrid between Poecilia species P. mexicana and P. latipinna. It reproduces by gynogenesis, which eliminates paternal genomic contribution to offspring. Earlier study showed that Amazon molly exhibits bi-allelic expression for a large portion of the genome, leading to two main questions: 1. Are the allelic expression patterns from the initial hybridization event stabilized or changed during establishment of the asexual species and its further evolution? 2. Is allelic expression biased toward one parental allele a stochastic or adaptive process? To answer these questions, the allelic expression of P. formosa siblings was assessed to investigate intra- and inter-cohort allelic expression variability. For comparison, interspecies hybrids between P. mexicana and P. latipinna were produced in the laboratory to represent the P. formosa ancestor. We have identified inter-cohort and intra-cohort variation in parental allelic expression. The existence of inter-cohort divergence suggests functional P. formosa allelic expression patterns do not simply reflect the atavistic situation of the first interspecies hybrid but potentially result from long-term selection of transcriptional fitness. In addition, clonal fish exhibit a transcriptional trend representing minimal intra-clonal variability in allelic expression patterns compared to the corresponding hybrids. The intra-clonal similarity in gene expression translates to sophisticated genetic functional regulation at the individuum level. These findings suggest the parental alleles inherited by P. formosa form tightly regulated genetic networks that lead to a stable transcriptomic landscape within clonal individuals.
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.