E number of top BLASTP hits are the Chicken (Gallus gallus

E number of top BLASTP hits are the Chicken (Gallus gallus), followed by the Carolina Anole Lizard (Anolis carolensis) and the Zebra Finch (Taeniopygio guttata). Since none of these species are model systems and thus are not especially well represented in the nr database, we normalized the number of hits to the number of proteins for each species in the NCBI protein database. Using this metric, T. scripta protein sequences are most similar to Wild Turkey (Meleagris gallopavo silvestris) sequences, closely followed by the Carolina Anole Lizard. If all three bird species are combined, however, T. scripta proteins are most similar to the Anole lizard, followed by the birds (Table 3). Determining the completeness of a transcriptome in a new species is difficult because of a lack of reference genomic sequences. One prediction about a relatively complete transcriptome is that all of the major GO categories Epigenetic Reader Domain should be well represented. We assigned cellular component (CC), molecular function (MF), and biological process (BP) GO terms to each protein in the transcriptome. CC terms describe the predictedcellular location of a protein, MF terms describe the predicted function of each protein, and BP terms describe the biological pathways that proteins are predicted to participate in. All major cellular compartments, molecular functions, and biological processes are well represented in our transcriptome. Biological process annotations include 7,564 and 7,200 proteins annotated with cell communication and multicellular organism development functions, respectively (Table S1). Another prediction about a complete transcriptome is that the enzymes that make up core metabolic pathways such as the TCA cycle should be well represented as the genes encoding these enzymes are expressed in all cells throughout development. We used Blast2Go to map each predicted protein onto the KEGG pathway database [34] which includes the TCA cycle as well as other core metabolic pathways. All of the enzymes required for the TCA cycle are represented in our transcriptome including, for example, both ADP and GDP forming Succinate CoA ligases (Table 4). In order for the sequences in our transcriptome to serve as a useful resource for turtle developmental biologists they must enable the identification of homologues 23148522 in other organisms and the generation of in situ probes. To demonstrate that our transcrip-Red-Eared Slider Turtle Embryonic TranscriptomeFigure 2. RT-PCR of developmentally important genes from a stage 17 T. scripta cDNA pool. doi:10.1371/journal.pone.0066357.gtome can be used to identify homologs of developmentally important genes we queried the transcriptome with developmental protein sequences from Epigenetics several species (chicken, zebrafish, humans, frogs, and the anole lizard when possible). Several of the genes we were interested in identifying (e.g., BMPs and FGFs) are members of gene families. For genes in these families, we identified multiple transcripts for each query. To determine the placement of each transcript within the gene family we constructed phylogenetic trees based on protein sequence similarity of all of the gene family members we identified. In most cases, it was possible to determine which family member each turtle transcript was most similar to, and in most cases the T. scripta transcriptome contains complete or nearly complete coverage of all members of each gene family. As an example, one of the gene families we investigatedwas the BMP family whic.E number of top BLASTP hits are the Chicken (Gallus gallus), followed by the Carolina Anole Lizard (Anolis carolensis) and the Zebra Finch (Taeniopygio guttata). Since none of these species are model systems and thus are not especially well represented in the nr database, we normalized the number of hits to the number of proteins for each species in the NCBI protein database. Using this metric, T. scripta protein sequences are most similar to Wild Turkey (Meleagris gallopavo silvestris) sequences, closely followed by the Carolina Anole Lizard. If all three bird species are combined, however, T. scripta proteins are most similar to the Anole lizard, followed by the birds (Table 3). Determining the completeness of a transcriptome in a new species is difficult because of a lack of reference genomic sequences. One prediction about a relatively complete transcriptome is that all of the major GO categories should be well represented. We assigned cellular component (CC), molecular function (MF), and biological process (BP) GO terms to each protein in the transcriptome. CC terms describe the predictedcellular location of a protein, MF terms describe the predicted function of each protein, and BP terms describe the biological pathways that proteins are predicted to participate in. All major cellular compartments, molecular functions, and biological processes are well represented in our transcriptome. Biological process annotations include 7,564 and 7,200 proteins annotated with cell communication and multicellular organism development functions, respectively (Table S1). Another prediction about a complete transcriptome is that the enzymes that make up core metabolic pathways such as the TCA cycle should be well represented as the genes encoding these enzymes are expressed in all cells throughout development. We used Blast2Go to map each predicted protein onto the KEGG pathway database [34] which includes the TCA cycle as well as other core metabolic pathways. All of the enzymes required for the TCA cycle are represented in our transcriptome including, for example, both ADP and GDP forming Succinate CoA ligases (Table 4). In order for the sequences in our transcriptome to serve as a useful resource for turtle developmental biologists they must enable the identification of homologues 23148522 in other organisms and the generation of in situ probes. To demonstrate that our transcrip-Red-Eared Slider Turtle Embryonic TranscriptomeFigure 2. RT-PCR of developmentally important genes from a stage 17 T. scripta cDNA pool. doi:10.1371/journal.pone.0066357.gtome can be used to identify homologs of developmentally important genes we queried the transcriptome with developmental protein sequences from several species (chicken, zebrafish, humans, frogs, and the anole lizard when possible). Several of the genes we were interested in identifying (e.g., BMPs and FGFs) are members of gene families. For genes in these families, we identified multiple transcripts for each query. To determine the placement of each transcript within the gene family we constructed phylogenetic trees based on protein sequence similarity of all of the gene family members we identified. In most cases, it was possible to determine which family member each turtle transcript was most similar to, and in most cases the T. scripta transcriptome contains complete or nearly complete coverage of all members of each gene family. As an example, one of the gene families we investigatedwas the BMP family whic.