ABSTRACT
The flatfish, Solea senegalensis has considerable scientific interest and commercial value. The metamorphosis in this species occurs between 12 and 19â¯days after hatching and it takes about 1â¯week to complete. Eleven Bacterial Artificial Chromosomes (BAC) clones containing the various candidate genes involved in the process of metamorphosis: thyroxine 5 deiodinase 3 (dio3); forkhead box protein E4 (foxe4); melatonin receptor type 1C (mel1c); calsequestrin 1b (casq1b); thyrotropin subunit beta (tshß); thyrotropin-releasing hormone receptor 1, 2, and 3 (trhr1, trhr2, trhr3); thyroid hormone receptor α a and b (thrαa, thrαb); and thyroid hormone receptor beta (thrß) were analyzed by multiple Fluorescence in situ Hybridization (mFISH) and Next Generation Sequencing (NGS) techniques. The mFISH technique localized the 11 BAC clones on 12 different chromosome pairs because three of them, specifically the trhr1a, trhr2 and thrß BAC clones, showed double signals. This signal duplication indicates a duplication of the genomic region inserted within the BAC clone, which provides evidence for the Teleost-Specific Whole Genome Duplication (TS-WGD). Micro-synteny and phylogenetic analysis showed that Cynoglossus semilaevis is the nearest species to S. senegalensis and that Danio rerio is the most distant one. The tshß BAC clone was highly conserved as the genes belonging to this BAC were located on a single chromosome in all the species studied. These genes participate in proliferation, migration and cell-death, which are key processes during metamorphosis. Overall, micro-synteny analysis showed that most candidate genes are found in conserved genomic surroundings.
Subject(s)
Flatfishes/growth & development , Flatfishes/genetics , Multigene Family , Animals , Chromosome Mapping , Fish Proteins/genetics , Gene Duplication , Genomics , Metamorphosis, Biological , PhylogenyABSTRACT
The Senegalese sole (Solea senegalensis) is commercially very important and a priority species for aquaculture product diversification. The main histone cluster was identified within two BAC clones. However, two replacement histones (H1.0 and H3.3) were found in another BAC clone. Different types of canonical histones H2A and H2B were found within the same species for the first time. Phylogenetic analysis demonstrated that the different types of H1, H2A, and H2B histones were all more similar to each other than to canonical histones from other species. The canonical histone H3 of S. senegalensis differs from subtypes H3.1 and H3.2 in humans at the site of residue 96, where a serine is found instead of an alanine. This same polymorphism has been found only in Danio rerio. The karyotype of S. senegalensis comprises 21 pairs of chromosomes, distributed in 3 metacentric pairs, 2 submetacentric pairs, 4 subtelocentric pairs, and 12 acrocentric pairs. The two BAC clones that contain the clusters of canonical histones were both mapped on the largest metacentric pair, and mFISH analysis confirmed the co-location with the dmrt1 gene in that pair. Three chromosome markers have been identified which, in addition to those previously described, account for 18 chromosome pairs in S. senegalensis.
Subject(s)
Fish Proteins/genetics , Flatfishes/genetics , Histones/genetics , Multigene Family , Amino Acid Sequence , Animals , Chromosome Mapping , Evolution, Molecular , Genetic Variation , Histones/classification , In Situ Hybridization, Fluorescence , Phylogeny , Sequence Homology, Amino AcidABSTRACT
We describe the cloning of a cDNA encoding TRH in Solea senegalensis. Phylogenetic analysis clustered it with other fish counterparts. Eight conserved TRH progenitors and highly divergent spacers were identified. Expression profiles of TRH were analyzed in juvenile tissues, during larval development, and in post-larvae grew under four photoperiods (12L:12D, 12D:12L, 24L:0D and 24D:0L) during four weeks using a real-time PCR approach. In juvenile fish, TRH mRNA was expressed ubiquitously although with the highest transcript levels in brain. During larval development, TRH mRNA levels were higher at 2-3days after hatching decreasing progressively until metamorphosis. Hormonal treatments using thiourea and T4 showed no regulation at transcriptional level by thyroid hormones. Moreover, no significant changes in mRNA levels between photoperiods at any time were detected. Overall, these results indicate that TRH do not participate in the regulation of HPT nor adaptation to photoperiod in sole.
