Update from Paul Hime and Joshua Reece, 2009 Recipients of the Ron Goellner Conservation Grant
The Search for Sex-Linked Genes in Cryptobranchid Salamanders: Genome-Wide Gene Discovery and Marker Development
Paul Hime1,2, David Weisrock2, Justin Kratovil2, Joshua Reece3,4
Accurate diagnosis of sex is an important aspect of conservation management efforts with endangered species, both in the wild and in captivity. However, in monomorphic species sex can be difficult to determine reliably. Such is the case with cryptobranchid salamanders, including the North American hellbender. Several non-genetic methods exist for determining hellbender sex, but each has limitations and none is universally reliable. Although sex chromosomes exist in cryptobranchids, they are weakly differentiated, suggesting that only a small portion of the genome varies between males and females. This study set out to design a genetic marker diagnostic for sex in hellbenders by identifying a region of the genome unique to one sex. Amplification of candidate sex-linked loci known from other amphibians and a preliminary AFLP analysis both failed to detect sex-linkage in a panel of known-sex hellbenders. Efforts are currently underway to identify hellbender-specific candidate sex-linked genes with high-throughput transcriptome sequencing of ovary and testis tissues, followed by in-silico subtraction of shared transcripts. In addition to gonadal transcriptome profiling, we are embarking on a gene discovery project using transcriptome sequencing of a variety of tissues from several individual hellbenders. In this marker development project, we expect to recover sequence data for large numbers of expressed genes, which will provide a genomic basis for addressing a wide range of important conservation questions in hellbenders.