Polysaccharides catabolism by the human gut bacterium -Bacteroides thetaiotaomicron: advances and perspectives.

In recent years, the degradation processes of polysaccharides by human gut microbiota are receiving considerable attention due to the discoveries of the powerful function of gut microbiota. Gut microbiota has developed a sensitive, accurate, and complex system for sensing, capturing, and degrading different polysaccharides. Among the gut microbiota, Bacteroides thetaiotaomicron, a representative species of Bacteroides, is considered as the best degrader of polysaccharides and a potential probiotic in pharmaceutical and food industries. Here, we summarize the degradation system of B. thetaiotaomicron and the degradation pathways of different polysaccharides by B. thetaiotaomicron. We also describe a technical route for investigating a specific polysaccharide degradation pathway by human gut bacteria. In addition, we also provide the future perspectives in the development of novel polysaccharides or oligosaccharides drugs, precision microbiology medicine, and personalized nutrition.

Wheat hypersensitive-induced reaction genes TaHIR1 and TaHIR3 are involved in response to stripe rust fungus infection and abiotic stresses.

KEY MESSAGE : TaHIR1 and TaHIR3 play positive roles in resistance to the stripe rust fungus via inducing HR and regulating defense-related genes, but are negatively regulated by various abiotic stimuli. Plant hypersensitive-induced reaction (HIR) genes are known to be associated with the hypersensitive response and disease defense. In wheat, two HIR genes, TaHIR1 and TaHIR3, have been identified and found to be up-regulated after infection with the stripe rust fungus. Here, we further determined their roles in defense against abiotic stresses and the stripe rust pathogen, Puccinia striiformis f. sp. tritici. TaHIR1 and TaHIR3 proteins were localized in the plasma membrane of tobacco cells. The expression of TaHIR1 and TaHIR3 was reduced by the environmental stimuli, including low temperature, drought, and high salinity stresses. In addition, the expression of TaHIR1 and TaHIR3 was down-regulated by exogenously applied ethrel and abscisic acid, whereas expression was not affected by treatments with salicylic acid and methyl jasmonate. Furthermore, barley stripe mosaic virus-induced gene silencing of TaHIR1 and TaHIR3 reduced resistance in wheat cultivar Suwon11 against an avirulent stripe rust pathotype CYR23 and area of necrotic cells neighboring the infection sites, and altered the expression levels of defense-related genes. These results suggest that TaHIR1 and TaHIR3 function positively in the incompatible interaction of wheat-stripe rust fungus, but exhibit negative transcriptional response to abiotic stresses.

A conidiation-related gene is highly expressed at the resting urediospore stage in Puccinia striiformis f. sp. tritici.

The production and germination of asexual spores in a diverse group of fungi play a crucial role in their infection cycles. These processes are regulated by a set of genes, namely, conidiation-related genes, involved in the production, morphological characteristics, and differentiation of conidia. In this study, we identified and characterized the PsCon1 gene, which is the first conidiation-related gene identified in Puccinia striiformis f. sp. tritici (Pst). Sequence analysis revealed that PsCON1 has two conserved conidiation-specific protein 6 domains. Single nucleotide polymorphisms and insertion/deletion variations were detected in the coding region of PsCon1 among five Pst races. Quantitative RT-PCR assays revealed that PsCon1 was expressed at the highest level in resting urediospores of Pst, and gradually decreased after germination and infection. However, at 312 hpi, at the stage of forming large amounts of urediospores on leaves, the amount of PsCon1 mRNA was sharply increased but only 0.1-fold that of resting urediospores. Subcellular localization assays indicated PsCon1 heterologously expressed in Fusarium graminearum was located in the cytoplasm of conidia. The results suggest that PsCon1 may play a role in formation or survival of Pst urediospores.

Structure Characterization and Anti-Rheumatoid Arthritis Activity of a Polysaccharide from Notopterygium incisum.

SCOPE: Notopterygium incisum is a traditional Chinese medicine that is commonly used to treat rheumatoid arthritis. Polysaccharides from N. incisum can be one of its main active components. However, there have been little investigations on N. incisum polysaccharides. METHODS AND RESULTS: A novel polysaccharide named NIP is extracted from N. incisum with a molecular weight of 2.34 × 106  Da. NIP, composed of arabinose, galactose, glucose, and galacturonic acid, is linked by methyl esterified 1,4-linked α-galacturonic acid, 1,6-linked ß-galactose, 1,5-linked α-arabinose, and 1,4,6-linked ß- glucose. In vitro, NIP can inhibit the NO production of LPS-stimulated RAW264.7 cells. In vivo, NIP relieves toe redness and swelling of AIA rats, reduces the release of inflammatory factors in the serum, and inhibits the activation of NF-κB and JAK/STAT3 signaling pathways. In addition, NIP can effectively decrease oxidative stress, reverse intestinal flora imbalance, and promote butyric acid-producing bacteria's proliferation to exert anti-RA activity. CONCLUSION: NIP may be recommended as a functional food that can alleviate the damage of rheumatoid arthritis.