First Evidence for Family-Specific QTL for Temperature-Dependent Sex Reversal in Nile Tilapia <b><i>(Oreochromis niloticus)</i></b>

Abstract

This study for the first time screens microsatellite markers for associations with the temperature-dependent sex of Oreochromis niloticus. Previous studies revealed markers on linkage groups (LG) 1, 3, and 23 to be linked to the phenotypic sex of Oreochromis spp. at normal rearing temperatures. Moreover, candidate genes for sex determination and differentiation have been mapped to these linkage groups. Here, 6 families of a temperature-treated genetically all-female (XX) F₁-population were genotyped for 21 microsatellites on the 3 LGs. No population-wide QTL (quantitative trait loci) or marker trait associations could be detected. However, family-specific QTL were found on LG 1 flanked by UNH995 and UNH104, on LG 3 at the position of GM213, and on LG 23 next to GM283. Moreover, family-specific single marker associations for UNH995 and UNH104 on LG 1, GM213 on LG 3, as well as for UNH898 and GM283 on LG 23 were detected. Yet, marker trait associations could not explain the temperature-dependent sex of all fish in the respective families. The molecular cue for the temperature-dependent sex in Nile tilapia might partially coincide with allelic variants at major and minor genetic sex determining factors. Moreover, additional QTL contributing to variable liabilities towards temperature might persist on other LGs.

The Reversible Sex of Gonochoristic Fish: Insights and Consequences

“…Associations were confirmed in a temperature-masculinized family which had a 66% male sex ratio [Palaiokostas et al, 2015]. Study of LGs linked to temperature-induced phenotypic male tilapias was performed by comparing a thermosensitive line versus a low or non-thermosensitive line showing a strong association of LG1, LG3, and LG23 [Lühmann et al, 2012]. A strong SNP association was also shown in LG20 in another family sensitive to temperature-masculinization using RADseq [Palaiokostas et al, 2015].…”

The Tilapias' Chromosomes Influencing Sex Determination

“…Apparently, these environmental influences are not random effects, and there is within-species genetic variation in the effect of temperature on sexual development [Wessels and Hörstgen-Schwark, 2007]. Recent linkage studies have placed loci corresponding to genetic factors involved in temperature-dependent sex determination on the same chromosomal regions as the major genetic sex-determination QTL on LG1, LG3 and LG23 [Lühmann et al, 2012].…”

Genetic architecture of sex determination in fish: applications to sex ratio control in aquaculture

“…In other species where major loci are involved, the application of QTL screening or genomic association analysis to look for the SD region demonstrated to be efficient and new SD-related genomic regions were identified (Martínez et al, 2009; Hermida et al, 2013), sometimes denoting important intraspecific variation such as in Eigenmannia or in cichlid species complex (Ser et al, 2010; Henning et al, 2011; Parnell and Streelman, 2013). As a consequence, selection has demonstrated to be efficient to change sex ratio in progenies of several species and in other related traits like the sensitivity to temperature on sex ratio (Baroiller et al, 2009; Liew et al, 2012; Lühmann et al, 2012; Lozano et al, 2013). …”

“…However, other sex-linked markers have been identified in O. niloticus and its hybrids ( O. niloticus x O. aureus ) mapping on LG3 and LG23 (Eshel et al, 2012). Also, it has been shown by linkage analysis that genetic factors are involved in the sensitivity of SD to temperature and that these factors are located depending on families on the same chromosomal regions as the major QTL at LG1, LG3, and LG23 (Lühmann et al, 2012). …”