Reactive oxygen species (ROS) are a major risk factor for the development of oxidation and inflammation. Ryegrass (pasture), a natural dietary fiber source, acts as an antioxidant with well-known anti-inflammatory properties. The current study aimed to examine the alkaline phosphatase (ALP)-dependent Kelch-like-ECH-associated protein 1- Nuclear factor erythroid 2-related factor 2 (Keap1-Nrf2) signaling pathway that facilitates the anti-oxidative and anti-inflammatory properties of pasture and its protective effects on ileal permeability, systemic inflammation, nutrient absorption, liver dysfunction, growth performance, intestinal organ development, and metabolic syndrome in commercial diet-challenged geese. The lipopolysaccharides (LPS), ALP, ROS, and tight junction proteins were determined from the ileum tissues, and the antioxidant enzymes, immunoglobulins, and metabolic syndrome were determined from liver tissues via Enzyme-linked immunosorbent assay (ELISA) kits. While the Nrf2 and LPS/ROS/Keap1-induced inflammatory cytokines were determined by the quantitative reverse transcription polymerase chain reaction (RT-qPCR) method. The intestinal morphology was examined by Hematoxylin and Eosin (H&E) staining to determine nutrient absorption in ileal tissues. Pasture-dependent ALP activity significantly ameliorated commercial diet-induced LPS and ROS-facilitated ileal barrier dysfunction and systemic inflammation. The pasture supplementation induced nutrient absorption by influencing intestinal organ development. Our biochemical assays showed that the activation of Nrf2 significantly increased antioxidant enzymes and immunoglobulins, and decreased Keap1 and malondialdehyde (MDA) concentrations in the liver tissues after pasture supplementation. The correlation analysis of ALP, LPS, ROS, and Keap1-Nrf2 pathway-dependent antioxidant enzymes with other host markers showed that pasture supplementation induced intestinal barrier function via reducing LPS/ROS-induced intestinal permeability and systemic inflammation in the ileum and liver tissues. Pasture intake might attenuate LPS/ROS-induced gut permeability, systemic inflammation, and metabolic syndrome and augment gut barrier functions, nutrient absorption, immunity, and growth performance, possibly by its Keap1-Nrf2 pathway-dependent antioxidant properties.

Salt stress is one of the major abiotic stresses that lead to crop yield reduction worldwide. Melatonin (MT), an endogenous hormone synthesized in plants, plays an important role in responding to abiotic stimuli such as drought, salinity, heat, cold, etc. However, the molecular mechanisms of MT-mediated abiotic stresses remain to be better understood. In order to explore the key genes and pathways of melatonin in alleviating salt stress, physiological and biochemical indicators as well as transcriptomics profile were conducted in alfalfa seedlings. The results showed that the germination rate, bud length and fresh weight of alfalfa seedlings added with melatonin were higher than those treated with salt alone. In addition, Malondialdehyde (MDA) and Superoxide anion (O2-) contents also displayed a decreasing trend. The activity and content of Superoxide dismutase (SOD)、peroxidase (POD) and Glutathione (GSH) increased to varying degrees. In order to further reveal the molecular mechanism of MT-mediated salt tolerance of alfalfa, transcriptome analysis was performed on alfalfa seedlings. 2,181 differentially expressed genes (DEGs) were obtained in the salt-treated group, including 780 upregulated genes and 1,401 down-regulated genes, while 4,422 DEGs were obtained in the MT group, among which 1,438 were upregulated and 2,984 were downregulated. By using GO functional annotation and KEGG pathway enrichment, we found that DEGs were mainly enriched in the biosynthesis of flavonoids, isoflavones, plant hormones, Glutathione (GSH), soluble sugars and other substances, as well as in the ABC transporter and MAPK signaling pathways. Among them, the DEGs in the MT group was more enriched in these pathways, suggesting that MT can combat salt stress by regulating the expression of genes related to phytohormone and antioxidant capacity, which has important reference value for the breeding of salt-tolerant alfalfa and other crops.

Salt stress is a major limiting factor for alfalfa yield due to its relatively low salt tolerance. High soil salinity adversely impacts alfalfa growth and development, leading to reduced yield. Melatonin (MT) is known to play a significant role in enhancing plant resistance to abiotic stresses. However, the mechanisms underlying melatonin-mediated abiotic stress responses, particularly salt stress, are not well understood. To address this gap, we conducted a study focusing on germinating alfalfa seeds under salt stress. Physiological indexes and transcriptomics analyses were carried out on the germinated seeds to investigate the effects of melatonin on alfalfa seedlings under salt stress conditions. Our results revealed that the application of melatonin led to an increase in shoot length and fresh weight of alfalfa seedlings under salt stress. Moreover, key physiological indexes such as peroxidase (POD) activity and glutathione (GSH) content were enhanced, while levels of malondialdehyde and superoxide anions decreased. Transcriptomic analysis identified a total of 2,131 differentially expressed genes in the salt-treated group, with 726 up-regulated and 1,405 down-regulated genes, while the MT-treated group showed 2896 differentially expressed genes, of which 1,097 were up-regulated and 1,799 were down-regulated. Further, KEGG enrichment analysis highlighted the enrichment of differentially expressed genes in pathways including flavonoid biosynthesis, ABC transporter, glutathione metabolism, and the MAPK signaling pathway, with these pathways more significantly enriched in the MT-treated group. These findings collectively suggest that melatonin plays a crucial role in alfalfa's response to salt stress and offer new insights into the genomic mechanisms underlying melatonin-mediated salt tolerance in alfalfa.