The sex-determining locus in the tiger pufferfish, Takifugu rubripes

Abstract

The tiger pufferfish (fugu), Takifugu rubripes, is a model fish that has had its genome entirely sequenced. By performing genomewide linkage analyses, we show that the sex of fugu is determined by a single chromosomal region on linkage group 19 in an XX-XY system.

Figure 1.—

Male and female meiotic maps of fugu LG19. The markers f2006, f542-2, and SDY (the locus determining male sex phenotype) showed no recombination. Genetic maps were generated using 75 males and 55 females from family 1. Allelic bridges are indicated by a line connecting female (left) and male (right) linkage maps. Genetic distances in centimorgans between adjacent markers are shown. Genotypes of markers are shown in supplemental data 2 (http://www.genetics.org/supplemental/). To produce progeny from the first family (family 1), we crossed an individual fugu male with an individual fugu female as described previously (Kai et al. 2005). We then created a second family by interspecific crossing. Takifugu niphobles is a species closely related to fugu with a shorter generation time. In our study, an individual fugu male was mated with an individual female T. niphobles and then a single F₁ hybrid male was crossed with a second female fugu. Sex was determined by histological examination of the gonads obtained from fish aged 8–10 months. The microsatellite loci were chosen by scanning scaffolds on electronic resources available from the Joint Genome Institute (http://genome.jgi-psf.org/Takru4/Takru4.home.html). Primer sequences for the markers used in this study are shown in supplemental data 1 at http://www.genetics.org/supplemental/ and deposited in DDBJ/EMBL/GenBank with accession nos. AB284949–AB284982. Genotyping with microsatellite markers was performed as described previously (Kai et al. 2005).