BUSCADOR RECOLECTA

Background Controlling sex ratios is essential for the aquaculture industry, especially in those species with sex dimorphism for relevant productive traits, hence the importance of knowing how the sexual phenotype is established in fish. Turbot, a very important fish for the aquaculture industry in Europe, shows one of the largest sexual growth dimorphisms amongst marine cultured species, being all-female stocks a desirable goal for the industry. Although important knowledge has been achieved on the genetic basis of sex determination (SD) in this species, the master SD gene remains unknown and precise information on gene expression at the critical stage of sex differentiation is lacking. In the present work, we examined the expression profiles of 29 relevant genes related to sex differentiation, from 60 up to 135 days post fertilization (dpf), when gonads are differentiating. We also considered the influence of three temperature regimes on sex differentiation. Results The first sex-related differences in molecular markers could be observed at 90 days post fertilization (dpf) and so we have called that time the onset of sex differentiation. Three genes were the first to show differential expression between males and females and also allowed us to sex turbot accurately at the onset of sex differentiation (90 dpf): cyp19a1a, amh and vasa. The expression of genes related to primordial germ cells (vasa, gsdf, tdrd1) started to increase between 75–90 dpf and vasa and tdrd1 later presented higher expression in females (90-105 dpf). Two genes placed on the SD region of turbot (sox2, fxr1) did not show any expression pattern suggestive of a sex determining function. We also detected changes in the expression levels of several genes (ctnnb1, cyp11a, dmrt2 or sox6) depending on culture temperature. Conclusion Our results enabled us to identify the first sex-associated genetic cues (cyp19a1a, vasa and amh) at the initial stages of gonad development in turbot (90 dpf) and to accurately sex turbot at this age, establishing the correspondence between gene expression profiles and histological sex. Furthermore, we profiled several genes involved in sex differentiation and found specific temperature effects on their expression., The study was supported by a project from the Spanish Ministerio de Ciencia e Innovación (AGL2010-22326-C02-01 and CDS2007-0002). Diego Robledo was supported by a FPU fellowship from the Ministerio de Educación Cultura y Deporte of the Spanish Government. Laia Ribas was supported by Aquagenomics and EpigenAqua postdoctoral contract, SI

20 pages, 10 figures, 7 additional files, [Background] Controlling sex ratios is essential for the aquaculture industry, especially in those species with sex dimorphism for relevant productive traits, hence the importance of knowing how the sexual phenotype is established in fish. Turbot, a very important fish for the aquaculture industry in Europe, shows one of the largest sexual growth dimorphisms amongst marine cultured species, being all-female stocks a desirable goal for the industry. Although important knowledge has been achieved on the genetic basis of sex determination (SD) in this species, the master SD gene remains unknown and precise information on gene expression at the critical stage of sex differentiation is lacking. In the present work, we examined the expression profiles of 29 relevant genes related to sex differentiation, from 60 up to 135 days post fertilization (dpf), when gonads are differentiating. We also considered the influence of three temperature regimes on sex differentiation., [Results] The first sex-related differences in molecular markers could be observed at 90 days post fertilization (dpf) and so we have called that time the onset of sex differentiation. Three genes were the first to show differential expression between males and females and also allowed us to sex turbot accurately at the onset of sex differentiation (90 dpf): cyp19a1a, amh and vasa. The expression of genes related to primordial germ cells (vasa, gsdf, tdrd1) started to increase between 75–90 dpf and vasa and tdrd1 later presented higher expression in females (90-105 dpf). Two genes placed on the SD region of turbot (sox2, fxr1) did not show any expression pattern suggestive of a sex determining function. We also detected changes in the expression levels of several genes (ctnnb1, cyp11a, dmrt2 or sox6) depending on culture temperature., [Conclusion] Our results enabled us to identify the first sex-associated genetic cues (cyp19a1a, vasa and amh) at the initial stages of gonad development in turbot (90 dpf) and to accurately sex turbot at this age, establishing the correspondence between gene expression profiles and histological sex. Furthermore, we profiled several genes involved in sex differentiation and found specific temperature effects on their expression., The study was supported by a project from the Spanish Ministerio de Ciencia e Innovación (AGL2010-22326-C02-01 and CDS2007-0002). Diego Robledo was supported by a FPU fellowship from the Ministerio de Educación Cultura y Deporte of the Spanish Government. Laia Ribas was supported by Aquagenomics and EpigenAqua postdoctoral contract.

Twelfth International Symposium on Genetics in Aquaculture 2015 - International Symposium on Genetics in Aquaculture XII (ISGA XII), 21-27 June 2015, Santiago de Compostela, Spain.-- 1 page, Controlling sex ratio is essential for the aquaculture industry, especially in those species with sex dimorphism for relevant productive traits. The turbot (Scophthalmus maximus), a very important fish for aquaculture industry in Europe, shows one of the largest sexual growth dimorphisms amongst marine cultured species, being the production of all female populations a desirable goal for industry. Although an important knowledge has been achieved on the genetic basis of sex determination (SD) in this species, the master SD gene remains unknown and precise information on key genes at the critical stage of sex differentiation is lacking. In the present work, we tackled the analysis of the expression profiles of 29 relevant genes related to sex differentiation from the first larval stages (60 days post fertilization, dpf) up to 135 dpf, when male and female gonads are differentiating. Also we considered the influence of three temperature regimes on the sex differentiation process. Three genes were the first to show differential expression between sexes and allowed us to sex turbot accurately at 90 dpf, considered as the time of the onset of sex differentiation: cyp19a1a, amh and vasa. Genes related to primordial germ cell (PGC) and PGC proliferation (vasa, gsdf, tdrd1) increased their expression between 75–90 dpf, and, specifically vasa and tdrd1, presented higher expression in females at more advanced stages (105 dpf). Furthermore, two genes present on the sex determining region of turbot were studied, sox2 and fxr1. Our results suggest that sox2 could be discarded as sex determining gene, while fxr1 presented an expression pattern which could be consistent with a function as sex determinant, being up-regulated in females at 105 dpf. We also detected significative changes in the expression level of several genes (for example cyp11a, dmrt2 or sox6) depending on culture temperature and our data suggest that the β-catenin could be involved in male-to-female sex reversal at cold temperatures, since the expression of ctnnb1 is higher at lower temperatures in males, Peer Reviewed