Global warming augments the risk of adverse pregnancy outcomes in vulnerable expectant mothers. Pioneering investigations into heat stress (HS) have predominantly centered on its direct impact on reproductive functions, while the potential roles of gut microbiota, despite its significant influence on distant tissues, remain largely unexplored. Our understanding of deleterious mechanisms of HS and the development of effective intervention strategies to mitigate the detrimental impacts are still limited. In this study, we aimed to explore the mechanisms by which melatonin targets gut microbes to alleviate HS-induced reproductive impairment. We firstly evaluated the alleviating effects of melatonin supplementation on HS-induced reproductive disorder in pregnant mice. Microbial elimination and fecal microbiota transplantation (FMT) experiments were then conducted to confirm the efficacy of melatonin through regulating gut microbiota. Finally, a lipopolysaccharide (LPS)-challenged experiment was performed to verify the mechanism by which melatonin alleviates HS-induced reproductive impairment. Melatonin supplementation reinstated gut microbiota in heat stressed pregnant mice, reducing LPS-producing bacteria (Aliivibrio) and increasing beneficial butyrate-producing microflora (Butyricimonas). This restoration corresponded to decreased LPS along the maternal gut-placenta-fetus axis, accompanied by enhanced intestinal and placental barrier integrity, safeguarding fetuses from oxidative stress and inflammation, and ultimately improving fetal weight. Further pseudo-sterile and fecal microbiota transplantation trials confirmed that the protective effect of melatonin on fetal intrauterine growth under HS was partially dependent on gut microbiota. In LPS-challenged pregnant mice, melatonin administration mitigated placental barrier injury and abnormal angiogenesis via the inactivation of the TLR4/MAPK/VEGF signaling pathway, ultimately leading to enhanced nutrient transportation in the placenta and thereby improving the fetal weight. Melatonin alleviates HS-induced low fetal weight during pregnancy via the gut-placenta-fetus axis, the first time highlighting the gut microbiota as a novel intervention target to mitigate the detrimental impact of global temperature rise on vulnerable populations.

Background: The rumen is the hallmark organ of ruminants, playing a vital role in their nutrition and providing products for humans. In newborn suckling ruminants milk bypasses the rumen, while in adults this first chamber of the forestomach has developed to become the principal site of microbial fermentation of plant fibers. With the advent of single-cell transcriptomics, it is now possible to study the underlying cell composition of rumen tissues and investigate how this relates the development of mutualistic symbiosis between the rumen and its epithelium-attached microbes.Results: We constructed a comprehensive cell landscape of the rumen epithelium, based on single-cell RNA sequencing of 49,689 high-quality single cells from newborn and adult rumen tissues. Our single-cell analysis identified six immune cell subtypes and seventeen non-immune cell subtypes of the rumen. On performing cross-species analysis of orthologous genes expressed in epithelial cells of cattle rumen and the human stomach and skin, we observed that the species difference overrides any cross-species cell-type similarity. Comparing adult with newborn cattle samples, we found fewer epithelial cell subtypes and more abundant immune cells, dominated by T helper type 17 cells in the rumen tissue of adult cattle. In newborns, there were more fibroblasts and myofibroblasts, anIGFBP3⁺epithelial cell subtype not seen in adults, while dendritic cells were the most prevalent immune cell subtype. Metabolism-related functions and the oxidation-reduction process were significantly upregulated in adult rumen epithelial cells. Using 16S rDNA sequencing, fluorescence in situ hybridization, and absolute quantitative real-time PCR, we found that epithelialDesulfovibriowas significantly enriched in the adult cattle. Integrating the microbiome and metabolome analysis of rumen tissues revealed a high co-occurrence probability ofDesulfovibriowith pyridoxal in the adult cattle compared with newborn ones while the scRNA-seq data indicated a stronger ability of pyroxidal binding in the adult rumen epithelial cell subtypes. These findings indicate thatDesulfovibrioand pyridoxal likely play important roles in maintaining redox balance in the adult rumen.Conclusions: Our integrated multi-omics analysis provides novel insights into rumen development and function and may facilitate the future precision improvement of rumen function and milk/meat production in cattle.

The composition of muscle fibers, characterized by distinct contractile and metabolic properties, significantly influences meat quality and glucose homeostasis. However, the mechanisms by which three-dimensional (3D) genome topology integrates with epigenetic states to regulate muscle fiber specification and transformation remain poorly understood. Here, we present an integrative analysis of the transcriptome, epigenome, and 3D genome architecture in the slow-twitch glycolytic extensor digitorum longus (EDL) and fast-twitch oxidative soleus (SOL) muscles of the pig (Sus scrofa). Global remodeling of enhancer-promoter (E-P) interactions emerged as a central driver of transcriptional reprogramming associated with muscle contraction and glucose metabolism. We identified tissue-specific super-enhancers (SEs) that regulate muscle fiber-type specification through cooperation of chromatin looping and transcription factors such as KLF5. Notably, the SE-driven activation of STARD7 facilitated the transformation of glycolytic fibers into oxidative fibers by mitigating reactive oxygen species levels and suppressing ERK MAPK signaling. This study elucidates the principles of 3D genome organization in the epigenetic regulation of muscle fiber specification and transformation, providing a foundation for novel therapeutic strategies targeting metabolic disorders and enhancing meat quality.

Genomic imprinting is manifested as monoallelic expression of genes according to parental origin, which is closely linked to mammalian placentation and human diseases. Yet, it is unclear how genomic imprinting evolves in different cell types. Here we generate a single-nucleus transcriptomic landscape of mammalian placental development, identifying 5 major cell types and 14 trophoblast subtypes. By developing a framework for integrating the datasets of single-nucleus transcriptome and whole-genome variations from reciprocal crosses of the genetically distinct Duroc and Lulai pig breeds, we construct a cell-type-specific genomic imprinting landscape, uncovering 118 candidate imprinted genes. We expand the mammalian imprinting gene catalog by identifying 97 previously uncharacterized imprinted candidates. Nearly 75% of imprinted candidates exhibit a cell-type- and developmental-stage-dependent manner. Through cross-species analysis, we show that cell-cell communication, especially the integration and modification of signaling pathways into a cell-type-specific autocrine network, drives biased allelic expression of imprinted genes in pigs, mice, and humans. Our findings provide genetic and molecular insights into parent-of-origin effects on gene expression, offering an in-depth understanding of genomic imprinting in mammals.

Mammals rely on their gut microbiota to degrade cellulose, the major component of dietary fiber. Westernized populations harbor a depleted microbiome with reduced fiber-digesting capacity and impaired immune regulation due to prolonged consumption of low-fiber diets. Comparable patterns are evident in other mammals, including Western commercial pigs raised on high-energy, low-fiber diets, exhibiting reduced diversity and abundance of fiber-degrading bacteria. In contrast, semi-free-ranging Chinese indigenous pigs consuming fiber-rich diets retain a more diverse and functionally resilient microbiota, reflecting divergent trajectories of host-microbiota co-evolution. However, the specific cellulose-degrading species lost and strategies to restore these functions remain unclear in mammals. By analyzing 473 human stool metagenomes spanning non-westernized and westernized diets, together with 251 fecal 16S rRNA datasets and 95 metagenomes from Western commercial pigs, Chinese indigenous pigs, and their crossbred progeny, we identified the Lachnospiraceae bacterium as a key symbiont enriched in non-westernized guts. This bacterium possesses an extensive Carbohydrate-Active Enzymes repertoire conferring strong fiber-degrading capacity. Notably, low-fiber diets leave a genetic signature on this keystone gut symbiont, which cannot be reversed by short-term dietary interventions alone. Reintroduction of Lachnospiraceae bacterium to germ-free mice improved feed efficiency and increased acetic acid production. Intestinal transcriptomics and peripheral blood flow cytometry revealed that it activates a broad adaptive immune response, promoting CD4⁺ T cell accumulation, B cell activation, and anti-inflammatory cytokine induction. Reintroduction of this bacterium also alleviated dextran sodium sulfate-induced colitis. These findings highlight the preclinical functional potential of this Lachnospiraceae bacterium in mitigating low-fiber diets-induced dysfunction in mammals.

Body conformation and carcass composition are economically important traits in pig production, yet their underlying genetic mechanisms remain incompletely characterized. To dissect the genetic bases of body length (BL), body height (BH), backfat thickness (BFT), and lean meat percentage (LMP), we estimated genetic parameters and performed a genome-wide association study (GWAS) using 50 K SNP array genotypes from 1527 Landrace pigs. Phenotypic variance decomposition revealed moderate-to-high heritability for all four traits, ranging from 0.23 for BH to 0.43 for BL. Genetic correlation analysis uncovered a strong negative correlation (−0.80 ± 0.05) between BFT and LMP, as well as a moderate positive correlation (0.46 ± 0.03) between BL and BH. Our GWAS identified 14 SNP–trait associations involving 10 unique SNPs and two genomic regions with overlapping association signals. On Sus scrofa chromosome 1 (SSC1), overlapping signals for BFT and LMP occurred near ABL1 and QRFP, whereas signals for body conformation mapped to SSC17 near BMP2, PROKR2, SLC23A2, and PCNA. These genes are positional and biologically plausible candidates, and these candidate markers hold potential for genomic selection to simultaneously improve body size and meat-production performance.