Project description:Purpose: The gene molecular network involved in teleost fish sex determination and differentiation is highly variable among species and even in some cases among populations of the same species. The objectives of the present study were to identify the period of gonadal sex differentiation in tambaqui juveniles, as well as the genes and pathways potentially involved in this process. Methods: Histological analysis of juveniles was carried out to establish a timeline of the gonadal differentiation in tambaqui. Based on that knowledge, ten juveniles were selected before the first evidence of histological sex differentiation and total RNA was extracted from their trunks and used for RNA-Sequencing and a subsequent de novo transcriptome assembly. Principal Component Analysis (PCA) of the whole transcriptome data was used to cluster samples into two distinct groups: putative males and putative females. Differential gene expression, functional annotation and gene enrichment were used to identify genes and pathways related to sex differentiation in tambaqui to which was applied the Mann-Whitney non-parametric t test (p <0.05) confirming the statistical significance of the expression dimorphism between the groups. Results: The first sign of histological sex differentiation in tambaqui was the formation of the ovarian cavity detected in individuals measuring about 40 mm in total length. Before the differentiation period, components of the Wnt / β-catenin pathway, fox and fst genes (p <0.05) suggest female sex development in the putative females, whereas antagonistic pathways (gsk3b, wt1 and fgfr2), sox9 and genes for androgen synthesis (p <0.05) are indicative of a male-like differentiation. Conclusions: Tambaqui juveniles prior to the morphological ovarian differentiation present the Wnt / β-catenin pathway exerting putative role on the sex differentiation target, either upregulated in female-like individuals, or antagonized in male-like individuals. Thus, the present work provides a molecular basis for future studies on the application of tambaqui monosex cultivation.
Project description:The interplay between phenotypic plasticity and adaptive evolution has long been an important topic of evolutionary biology. This process is critical to our understanding of a species evolutionary potential in light of rapid climate changes. Despite recent theoretical work, empirical studies of natural populations, especially in marine invertebrates, are scarce. In this study, we investigated the relationship between adaptive divergence and plasticity by integrating genetic and phenotypic variation in Pacific oysters from its natural range in China. Genome resequencing of 371 oysters revealed unexpected fine-scale genetic structure that is largely consistent with phenotypic divergence in growth, physiology, thermal tolerance and gene expression across environmental gradient. These findings suggest that selection and local adaptation are pervasive and together with limited gene flow shape adaptive divergence. Plasticity in gene expression is positively correlated with evolved divergence, indicating that plasticity is adaptive and likely favored by selection in organisms facing dynamic environments such as oysters. Divergence in heat response and tolerance implies that the evolutionary potential to a warming climate differs among oyster populations. We suggest that trade-offs in energy allocation are important to adaptive divergence with acetylation playing a role in energy depression under thermal stress.
Project description:Brazil has five climatically distinct regions, with an annual average temperature difference up to 14 ºC between the northern and southern extremes. Environmental variation of this magnitude can lead to new genetic patterns among farmed fish populations. Genetically differentiated populations of tambaqui (Colossoma macropomum Cuvier, 1818), an important freshwater fish for Brazilian continental aquaculture, may be associated with regional adaptation. In this study, we selected tambaquis raised in two thermally distinct regions, belonging to different latitudes, to test this hypothesis. De novo transcriptome analysis was performed to compare the significant differences of genes expressed in the liver of juvenile tambaqui from a northern population (Balbina) and a southeastern population (Brumado). In total, 2,410 genes were differentially expressed (1,196 in Balbina and 1,214 in Brumado). Many of the genes are involved in a multitude of biological functions such as biosynthetic processes, homeostasis, biorhythm, immunity, cell signaling, ribosome biogenesis, modification of proteins, intracellular transport, structure/cytoskeleton, and catalytic activity. Enrichment analysis based on biological networks showed a different protein interaction profile for each population, whose encoding genes may play potential functions in local thermal adaptation of fish to their respective farming environments.