The gut-brain-gonad axis mediates salinity adaptation in an invasive turtle: causal evidence from microbiota transplantation and metabolite supplementation.

backgroundPreliminary studies have shown that salinity stress can impair the differentiation of spermatogonial stem cells (SSC) in red-eared slider (Trachemys scripta elegans) through the gut-brain-gonad axis, thereby affecting their reproductive ability. However, a direct causal link between salinity-induced gut microbiota alterations and reproductive suppression remains unclear. To test the hypothesis that gut microbiota and their metabolites mediate salinity adaptation by modulating the gut-brain-gonad axis, we conducted fecal microbiota transplantation (FMT) and metabolite supplementation experiments.

resultsResults showed that the FMT group successfully recapitulated the donor's gut microbial profile and exhibited significant changes in intestinal metabolites. Both FMT and GABA supplementation mimicked the reproductive inhibitory phenotype observed under direct salinity stress: altered brain neurotransmitter levels (increased dopamine, decreased serotonin), downregulated expression of reproductive genes (e.g. GnRH1, FSHβ), and impaired SSC self-renewal and differentiation in testes, as evidenced by reduced marker gene expression (e.g. PLZF, Stra8) and disrupted testicular histology.

conclusionOur findings demonstrate that salinity stress reshapes the gut microbiota and metabolome. This leads to increased inhibitory signaling, notably via GABA, along the gut-brain-gonad axis. Ultimately, this signaling cascade suppresses reproductive function. This study provides novel mechanistic insights into the environmental adaptation strategies of an invasive species and highlights the potential of targeting the microbiome-metabolite axis for developing innovative, environmentally friendly biocontrol approaches against this invasive species.