Biology subjects

Primmer, C.

Publications and source records attributed to Primmer, C..

3 recordsLinked to original sources

bioRxiv2021

Strong regulatory effects of vgll3 genotype on reproductive axis gene expression in immature male Atlantic salmon

Age at maturity is a major contributor to the diversity of life history strategies in organisms. The process of maturation is influenced by both genetics and the environment, and includes changes in levels of sex hormones and behavior, but the specific factors leading to variation in maturation timing are not well understood. gnrh1 regulates the transcription of gonadotropin genes at the onset of puberty in many species, but this gene is lacking in certain teleost species including Atlantic salmon (Salmo salar), which raises the possibility of the involvement of other important regulatory factors during this process. Earlier research has reported a strong association of alternative alleles of the vgll3 gene with maturation timing in Atlantic salmon, suggesting it as a potential candidate regulating reproductive axis genes. Here, we investigated the expression of reproductive axis genes in immature Atlantic salmon males with different vgll3 genotypes during the spawning period. We detected strong vgll3 genotype-dependent differential expression of reproductive axis genes (such as fshb, lhb, amh and igf3) tested in the pituitary, and testis of one-year-old immature male Atlantic salmon. In addition, we observed differential expression of jun (ap1) and nr5a1b (sf1), potential upstream regulators of gonadotropins in the pituitary, as well as axin2, id3, insl3, itch, ptgs2a and ptger4b, the downstream targets of amh and igf3 in the testis. Hereby, we provide evidence of strong vgll3 genotype-dependent transcriptional regulation of reproductive axis genes prior to sexual maturation together with models for distinct actions of vgll3 genotypes on the molecular processes controlling spermatogenesis in Atlantic salmon.

physiology↗

bioRxiv2018

Genomic signatures of fine-scale local adaptation in Atlantic salmon suggest involvement of sexual maturation, energy homeostasis, behaviour, and immune defence-related genes.

Elucidating the genetic basis of adaptation to the local environment can improve our understanding of how the diversity of life has evolved. In this study we used a dense SNP array to identify candidate loci underlying fine-scale local adaptation within a large Atlantic salmon (Salmo salar) population. By combining outlier, gene-environment association, and haplotype homozygosity analyses, we identified multiple regions of the genome with strong evidence for diversifying selection. Several of these candidate regions had previously been identified in other studies, demonstrating that the same loci be adaptively important in Atlantic salmon at sub-drainage, regional and continental scales. Notably, we identified signals consistent with local selection around genes associated with variation in sexual maturation, energy homeostasis, behaviour, and immune defence. These included the large-effect age-at-matunty gene vgll3, the known obesity gene mc4r, and major histocompatibility complex II. Most strikingly, we confirmed a genomic region on Ssa09 that was extremely differentiated among subpopulations, and that is also a candidate for local selection over the global range of Atlantic salmon. This region co-localized with a genomic region strongly associated with spawning ecotype in sockeye salmon (Oncorhynchus nerka), with circumstantial evidence that the same gene (six6) may be the selective target in both cases. The phenotypic effect of this region in Atlantic salmon remains cryptic, although allelic variation is related to river flow volume and co-vanes with timing of the return spawning migration. Our results further inform management of Atlantic salmon and open multiple avenues for future research.

evolutionary biology↗

bioRxiv2017

Modularity Facilitates Flexible Tuning Of Plastic And Evolutionary Gene Expression Responses During Early Divergence

Gene expression changes have been recognized as important drivers of adaptation to changing environmental conditions. Little is known about the relative roles of plastic and evolutionary responses in complex gene expression networks during the early stages of divergence. Large gene expression data sets coupled with in silico methods for identifying co-expressed modules now enable systems genetics approaches also in non-model species for better understanding of gene expression responses during early divergence. Here, we combined gene co-expression analyses with population genetics to separate plastic and population (evolutionary) effects in expression networks using small salmonid populations as a model system. We show that plastic and population effects were highly variable among the six identified modules and that the plastic effects explained larger proportion of the total eigengene expression than population effects. A more detailed analysis of the population effects using a QST - FST comparison across 16622 annotated transcripts revealed that gene expression followed neutral expectations within modules and at the global level. Furthermore, two modules showed enrichment for genes coding for early developmental traits that have been previously identified as important phenotypic traits in thermal responses in the same model system indicating that co-expression analysis can capture expression patterns underlying ecologically important traits. We suggest that module-specific responses may facilitate the flexible tuning of expression levels to local thermal conditions. Overall, our study indicates that plasticity and neutral evolution are the main drivers of gene expression variance in the early stages of thermal adaptation in this system.

evolutionary biology↗