Project description:Background: Food supply is a major factor influencing growth rates in animals. This has important implications for both natural and farmed fish populations, since food restriction may difficult reproduction. However, a study on the effects of food supply on the development of juvenile gonads has never been transcriptionally described in fish. Methods and Findings: This study investigated the consequences of growth on gonadal transcriptome of European sea bass in: 1) 4-month-old sexually undifferentiated fish, comparing the gonads of fish with the highest vs. the lowest growth, to explore a possible link between transcriptome and future sex, and 2) testis from 11-month-old juveniles where growth had been manipulated through changes in food supply. The four groups used were: i) sustained fast growth, ii) sustained slow growth, iii) accelerated growth, iv) decelerated growth. The transcriptome of undifferentiated gonads was not drastically affected by initial natural differences in growth. Further, changes in the expression of genes associated with protein turnover were seen, favoring catabolism in slow-growing fish and anabolism in fast-growing fish. Moreover, while fast-growing fish took energy from glucose, as deduced from the pathways affected and the analysis of protein-protein interactions examined, in slow-growing fish lipid metabolism and gluconeogenesis was favored. Interestingly, the highest transcriptomic differences were found when forcing initially fast-growing fish to decelerate their growth, while accelerating growth of initially slow-growing fish resulted in full transcriptomic convergence with sustained fast-growing fish. Conclusions: Food availability during sex differentiation shapes the juvenile testis transcriptome, as evidenced by adaptations to different energy balances. Remarkably, this occurs in absence of major histological changes in the testis. Thus, fish are able to recover transcriptionally their testes if they are provided with enough food supply during sex differentiation; however, an initial fast growth does not represent any advantage in terms of transcriptional fitness if later food becomes scarce.

Project description:Fish respond to stressors by means of an array of changes that involve many biological compartments including molecular, cellular, metabolic, physiological and behavioral acclimation. Among these changes, the immune system also experiences significant alterations that are characterized by an induction of the innate non-specific responses and changes in the acquired specific response. The present investigation was undertaken to check whether the innate response of the complement system is affected after a combination of an immune challenge and a husbandry stressor. In European seabass, two different transcripts of the complement C3 protein, which correspond to two tissue-specific isoforms, have been detected in liver. They may come from post-transcriptional modifications at the pre-mRNA level or from alternative splicing in order to generate a diversified repertoire of protein isoforms in some fish species according to the tissue were they are located. After cloning the hepatic C3, the quantification of seabass isoforms showed specific responses, thus confirming the possible specialized roles of the C3 different isoforms in terms of defence immunity. On one hand, a stronger esbC3_2 expression was observed in front to the viral challenge, suggesting a specific participation of this molecule in front to viruses. This observation is in agreement with previous studies in trout macrophages in our lab, demonstrating that the immune response to viral infections was stronger than to bacterial ones. On the other hand, the esbC3_1 expression appeared stronger after bacterial challenge, especially under high density conditions. Our results confirm the hypothesis of an immune-activation of specific isoforms of the C3 protein of the complement system as a non-specific response in front to either immune or other type of stressors. In order to confirm our hypothesis, we created an oligonucleotide microarray (Agilent Technologies) containing 6275 annotated transcripts, each with x3 specific probes, and 4516 ESTs with 1 probe/target sequence. Gene expression profiles obtained from the livers of fish held under high density culture conditions highlighted a significant contrast in the liver response. In total, 54 transcripts were differentially expressed (GDE; fold change FC >2) in treatment over the control (p<0.01)/201 (p<0.05).

Project description:Fish respond to stressors by means of an array of changes that involve many biological compartments including molecular, cellular, metabolic, physiological and behavioral acclimation. Among these changes, the immune system also experiences significant alterations that are characterized by an induction of the innate non-specific responses and changes in the acquired specific response. The present investigation was undertaken to check whether the innate response of the complement system is affected after a combination of an immune challenge and a husbandry stressor. In European seabass, two different transcripts of the complement C3 protein, which correspond to two tissue-specific isoforms, have been detected in liver. They may come from post-transcriptional modifications at the pre-mRNA level or from alternative splicing in order to generate a diversified repertoire of protein isoforms in some fish species according to the tissue were they are located. After cloning the hepatic C3, the quantification of seabass isoforms showed specific responses, thus confirming the possible specialized roles of the C3 different isoforms in terms of defence immunity. On one hand, a stronger esbC3_2 expression was observed in front to the viral challenge, suggesting a specific participation of this molecule in front to viruses. This observation is in agreement with previous studies in trout macrophages in our lab, demonstrating that the immune response to viral infections was stronger than to bacterial ones. On the other hand, the esbC3_1 expression appeared stronger after bacterial challenge, especially under high density conditions. Our results confirm the hypothesis of an immune-activation of specific isoforms of the C3 protein of the complement system as a non-specific response in front to either immune or other type of stressors. In order to confirm our hypothesis, we created an oligonucleotide microarray (Agilent Technologies) containing 6275 annotated transcripts, each with x3 specific probes, and 4516 ESTs with 1 probe/target sequence. Gene expression profiles obtained from the livers of fish held under high density culture conditions highlighted a significant contrast in the liver response. In total, 54 transcripts were differentially expressed (GDE; fold change FC >2) in treatment over the control (p<0.01)/201 (p<0.05). Oligonucleotide probes were used to construct a high-density seabass microarray based on the Agilent 4 × 44 K design format (http://www.agilent.com/), which covers 13,199 unique transcripts of Dicentrarchus labrax. Oligonucleotides, 60-mer plus a “linker”, are synthesized directly on glass slides using the Agilent’s SurePrint Tecnology; oligo design was carried out by Agilent and three or more non-overlapping probes were designed for each EST cluster. The number of transcripts represented by three is 6,275, while 6,924 targets EST have only one probe.

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Dicentrarchus labrax

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