Genetic map of male <i>Strongylocentrotus intermedius</i>.

<p>Genetic map of male <i>Strongylocentrotus intermedius</i>.</p

Genome wide distribution of LOD scores for body size.

<p>The red bars show the LOD generated from permutation tests (n = 5,000).</p

Genotyping and filtering of SNP markers for genetic mapping.

<p>A) Distribution of markers assessed by SNP call rate; B) Distribution of samples assessed by sample call rate.</p

High-Density Genetic Mapping with Interspecific Hybrids of Two Sea Urchins, <i>Strongylocentrotus nudus</i> and <i>S</i>. <i>intermedius</i>, by RAD Sequencing

<div><p>Sea urchins have long been used as research model organisms for developmental biology and evolutionary studies. Some of them are also important aquaculture species in East Asia. In this work, we report the construction of RAD-tag based high-density genetic maps by genotyping F₁ interspecific hybrids derived from a crossing between a female sea urchin <i>Strongylocentrotus nudus</i> and a male <i>Strongylocentrotus intermedius</i>. With polymorphisms present in these two wild individuals, we constructed a female meiotic map containing 3,080 markers for <i>S</i>. <i>nudus</i>, and a male meiotic map for <i>S</i>. <i>intermedius</i> which contains 1,577 markers. Using the linkage maps, we were able to anchor a total of 1,591 scaffolds (495.9 Mb) accounting for 60.8% of the genome assembly of <i>Strongylocentrotus purpuratus</i>. A genome-wide scan resulted in the identification of one putative QTL for body size which spanned from 25.3 cM to 30.3 cM. This study showed the efficiency of RAD-Seq based high-density genetic map construction using F₁ progenies for species with no prior genomic information. The genetic maps are essential for QTL mapping and are useful as framework to order and orientate contiguous scaffolds from sea urchin genome assembly. The integration of the genetic map with genome assembly would provide an unprecedented opportunity to conduct QTL analysis, comparative genomics, and population genetics studies.</p></div

QTL plots for body size on linkage group 5.

<p>QTL plots for body size on linkage group 5.</p

Identification of growth-related genes from the QTL region based on the genome assembly of <i>Strongylocentrotus purpuratus</i>.

<p>Identification of growth-related genes from the QTL region based on the genome assembly of <i>Strongylocentrotus purpuratus</i>.</p

Generation of sequence tags with RAD-Seq.

<p>Generation of sequence tags with RAD-Seq.</p

Summary of genetic maps of <i>Strongylocentrotus nudus</i> and <i>S</i>. <i>intermedius</i>.

<p>Summary of genetic maps of <i>Strongylocentrotus nudus</i> and <i>S</i>. <i>intermedius</i>.</p