Fig. 3

Expression and sequence variation of candidate genes. a Transcript abundance histogram showing the expression of PTGDSL and CASRL in 11 tissues of Nile tilapia. Data of RNA sequencing of Oreochromis niloticus from a project in which each tissue sample was sequenced in three runs (GenBank accession No. PRJNA78915) was meta-analyzed and transcript abundance was estimated in fragments per kilobase of transcript per million (FPKM). The standard error was approximated from three runs (error bars). b Typical sequencing chromatograms of the second exon of CASRL. Genomic DNA extracted from Oreochromis aureus males (n = 4) and responsive and non-responsive females (n = 10, each) was sequenced using Sanger sequencing of a PCR amplicon (Table 1) from the forward primer. Three arrows point to three polymorphic positions that encode I130V, V131L amino acid variations, and a synonymous nucleotide substitution. A larger fourth arrow indicates the first position in the codon for the methionine (ATG), which is missing in the gene variant with the shorter exon 2