Meeting Abstract
S11-2.2 Monday, Jan. 7 Genetics, Genomics, and the Evolution of Temperature-dependent Sex Determination in Reptiles RHEN, Turk*; SCHROEDER, Anthony; FAGERLIE, Ruby; LEGGE, Heath; WESSMAN, Laurel; HEIMLER, Jon; BONAPACE-POTVIN, Michelle; ZHANG, Kurt; University of North Dakota turk.rhen@email.und.edu
Temperature-dependent sex determination (TSD) is found in some fish and amphibians and many reptiles. Yet, the gene(s) that transduces temperature into a signal for ovary versus testis development is not known in any species. We are using genomic and genetic approaches to dissect the molecular basis for TSD in the snapping turtle, Chelydra serpentina. We used “next generation” sequencing to characterize the transcriptome in gonads from embryos incubated under male and female thermal regimes. We used the 454 system to sequence two normalized libraries, producing 2.8 million reads (1.4 million/temp) with average read length of 350 bp. We assembled and annotated these sequences. In a second study, we used the Illumina platform to sequence 20 RNA samples (2 temps x 5 days x 2 biological replicates). This study produced 156.4 million reads (100 bases/read) for a total of more than 15 trillion bp of cDNA sequence. We used DEseq within the R statistical package to analyze transcript abundance (i.e., reads/contig). We identified numerous differentially expressed transcripts during the temperature sensitive period of sex determination: 302 genes on day 1, 145 genes on day 2, 247 genes on day 3, 630 genes on day 4, and 1071 genes on day 5. We used quantitative PCR to verify differential expression of candidate genes. We are also identifying polymorphisms in candidate genes. These polymorphisms will be used in allele specific expression assays in embryonic gonads and genetic association studies in hatchlings from a temperature that produces mixed sex ratios. Here we report results of our transcriptome analyses and describe results of structural equation modeling of the gene network underlying TSD. We discuss TSD within the context of the reproductive biology and ecology of the snapping turtle.
