1. Research addressing the role of epigenetics in a diversity of experimental and natural systems is rapidly accumulating. Diverse methods have been developed to study epigenetic states, including bisulfite sequencing and AFLP-based approaches. However, existing methods are sometimes difficult to apply to non-traditional model organisms that lack genomic resources (bisulfite sequencing), and can fail to be economical and readily scalable to diverse research questions because of reliance on traditional Sanger sequencing (AFLP approaches). 2. Here we develop a reduced-representation library-based approach that is scalable and economical to quantitatively compare patterns of genome-wide methylation. This approach shares substantial similarity to the now widely used double digest restriction-site associated DNA sequencing-based method (ddRADseq), except that it utilizes a methylation-sensitive restriction enzyme. This method therefore identifies changes in the genomic methylation state of cytosine (to 5-methyl-cytosine; 5mC) by sampling loci (via next-generation sequencing) that are not methylated within a sample. We test this method to identify shifts in the epigenome of clonal water fleas (Daphnia ambigua) in response to exposure to fish predator cues, which are known to induce transgenerational changes in life history traits. 3. We found evidence for differential transgenerational responses (inferred via significant shifts in the methylation state of sampled loci) to predator cues among our treatment groups, and remarkably consistent responses within treatment groups. Our results demonstrate that this method is capable of producing highly repeatable results even without the use of a reference genome. 4. Applications of this general method are broad and diverse, and include the analysis of epigenetic shifts in both experimental and natural study systems.
Daphnia ambigua epiRADseq Pseudo-reference Genome
The pseudo-reference genome was constructed using all epiRAD reads, which was used for read mapping and inferring methylation. This file is in fasta format and is compressed.
Daphnia_ambigua_EpiRADseq_Reference.fasta.bz2
Daphnia ambigua epiRADseq Mapping Output Files
A zipped archive containing BAM mapping files for each sample (3 replicates across 2 treatments) mapped to the Daphnia ambigua pseudo-reference genome.
Daphnia_ambigua_EpiRADseq_Mapping_Files.tar.bz2
Daphnia ambigua EpiRADseq Raw Count Tables
A zipped archive containing the raw counts for each sample (3 replicates across 2 treatments) derived from the mapping to the Daphnia ambigua pseudo-reference genome. The four columns (in order) are: (1) The reference sequence/contig ID, (2) The length of the sequence/contig, (3) The number of reads that mapped to the sequence/contig, and (4) the number of reads that didn't map to the sequence/contig.
Daphnia_ambigua_EpiRADseq_Raw_Counts.tar.bz2
Daphnia ambigua P treatment - first generation with predatory cues treatment (3 replicates) - Raw Illumina Reads
A zipped fastq file that contains multiplexed reads from the three replicates from the predator treatment (generation 1). A script within the Data_processing_scripts.tar.bz archive will automatically perform the parsing using a barcodes file located in that same archive. These replicates are referred to as the P treatments in the manuscript and with all applicable Dryad file names and processing steps.
P_Gen1_Predator_Treatment.fastq.bz2
Daphnia ambigua PN treatment - second generation without predatory cues treatment (3 replicates) - Raw Illumina Reads
A zipped fastq file that contains multiplexed reads from the three replicates from the no predator treatment (generation 2). A script within the Data_processing_scripts.tar.bz archive will automatically perform the parsing using a barcodes file located in that same archive. These replicates are referred to as the PN treatments in the manuscript and with all applicable Dryad file names and processing steps.
PN_Gen2_NoPredator_Treatment.fastq.bz2
Frequency summary of Daphnia pulex genome double digest
A summary file that provides the number of fragments in given fragment size range. Based on an in silico digestion of the Daphnia pulex genome. The Perl script used to generate this data is contained with all other data processing scripts.
Daphnia_pulex_summary_doubleDigest_CTGCAG_CCGG.txt
Daphnia ambigua EpiRADseq Data Analysis Scripts, Files, & Documentation
A zipped archive containing all scripts necessary to quality-trim raw reads, construct the pseudo-reference genome, and map the reads back to the psuedo-reference to infer methylation. Each script contains a proper description of function and usage and the complete pipeline (from raw reads to counts) is automated and documented in the EpiRADseq_analysis.sh script.
Data_processing_scripts.tar.bz2
Daphnia ambigua EpiRADseq Rarefaction Raw Read Files
A zipped archive containing randomly subsetted read files from all replicates, which were used for rarefaction analysis.
Rarefaction_Daphnia_ambigua_EpiRADseq_Raw_Reads.tar.bz2
Daphnia ambigua EpiRADseq Rarefaction Mapping Files
A zipped archive containing BAM mapping files for each rarefacted sample (3 replicates across 2 treatments) mapped to the Daphnia ambigua pseudo-reference genome.
Rarefaction_Daphnia_ambigua_EpiRADseq_Mapping_Files.tar.bz2
Daphnia ambigua EpiRADseq Rarefaction Raw Count Tables
A zipped archive containing the raw counts for each rarefacted sample (3 replicates across 2 treatments) derived from the mapping to the Daphnia ambigua pseudo-reference genome. The four columns (in order) are: (1) The reference sequence/contig ID, (2) The length of the sequence/contig, (3) The number of reads that mapped to the sequence/contig, and (4) the number of reads that didn't map to the sequence/contig.
Rarefaction_Daphnia_ambigua_EpiRADseq_Raw_Counts.tar.bz2