Mogroside V reduced the excessive endoplasmic reticulum stress and mitigated the Ulcerative colitis induced by dextran sulfate sodium in mice.

Ulcerative colitis (UC) is an idiopathic, chronic inflammatory condition of the colon, characterized by repeated attacks, a lack of effective treatment options, and significant physical and mental health complications for patients. The endoplasmic reticulum (ER) is a vital intracellular organelle in maintaining cellular homeostasis. Endoplasmic reticulum stress (ERS) is induced when the body is exposed to adverse external stimuli. Numerous studies have shown that ERS-induced apoptosis plays a vital role in the pathogenesis of UC. Mogroside V (MV), an active ingredient of Monk fruit, has demonstrated excellent anti-inflammatory and antioxidant effects. In this study, we investigated the therapeutic effects of MV on dextran sulfate sodium (DSS)-induced UC and its potential mechanisms based on ERS. The results showed that MV exerted a protective effect against DSS-induced UC in mice as reflected by reduced DAI scores, increased colon length, reduced histological scores of the colon, and levels of pro-inflammatory cytokines, as well as decreased intestinal permeability. In addition, the expression of ERS pathway including BIP, PERK, eIF2α, ATF4, CHOP, as well as the apoptosis-related protein including Caspase-12, Bcl-2 and Bax, was found to be elevated in UC. However, MV treatment significantly inhibited the UC and reversed the expression of inflammation signaling pathway including ERS and ERS-induced apoptosis. Additionally, the addition of tunicamycin (Tm), an ERS activator, significantly weakened the therapeutic effect of MV on UC in mice. These findings suggest that MV may be a therapeutic agent for the treatment of DSS-induced UC by inhibiting the activation of the ERS-apoptosis pathway, and may provide a novel avenue for the treatment of UC.

The role of endoplasmic reticulum stress in regulation of intestinal barrier and inflammatory bowel disease.

Inflammatory bowel disease (IBD) is a chronic inflammatory disease involving the digestive tract, characterized by abdominal pain, diarrhea, rectal bleeding, and so on, which can make patients physically weakened and live difficultly. Although IBD has been recognized for many years, the pathogenesis of IBD has not yet been established and damage to intestinal barrier is thought to be closely associated with IBD. Intestinal barrier is an innate barrier that maintains the homeostasis of the intestinal environment and impedes pathogenic bacteria and toxins, and the endoplasmic reticulum (ER) has recently been found to be involved in maintaining the integrity of intestinal barrier. Endoplasmic reticulum stress (ERS) is a status of endoplasmic reticulum damaged when unfolded or misfolded proteins accumulate in excess of the degradation systematic clearance limit of the misfolded proteins. The regulation of ERS on protein folding synthesis and maintenance of cellular homeostasis is an important factor in influencing the integrity of the intestinal barrier. This paper mainly discusses the relationship between ERS and the intestinal barrier, aiming to understand the regulatory role of ERS on the intestinal barrier and the mechanism and to improve new solutions and notions for the treatment or prevention of IBD.

Functional divergence of a pair of Arabidopsis phospho-base methyltransferases, PMT1 and PMT3, conferred by distinct N-terminal sequences.

In seed plants, phospho-base N-methyltransferase (PMT) catalyzes a key step in the biosynthesis pathway of phosphatidylcholine (PC), the most abundant phospholipid class. Arabidopsis thaliana possesses three copies of PMT, with PMT1 and PMT3 play a primary role because the pmt1 pmt3 double mutant shows considerably reduced PC content with a pale seedling phenotype. Although the function of PMT1 and PMT3 may be redundant because neither of the parental single mutants showed a similar mutant phenotype, major developmental defects and possible functional divergence of these PMTs underlying the pale pmt1 pmt3 seedling phenotype are unknown. Here, we show the major developmental defect of the pale seedlings in xylem of the hypocotyl with partial impairments in chloroplast development and photosynthetic activity in leaves. Although PMT1 and PMT3 are localized at the endoplasmic reticulum, their tissue-specific expression pattern was distinct in hypocotyls and roots. Intriguingly, the function of PMT3 but not PMT1 requires its characteristic N-terminal sequence in addition to the promoter because truncation of the N-terminal sequence of PMT3 or substitution with PMT1 driven by the PMT3 promoter failed to rescue the pale pmt1 pmt3 seedling phenotype. Thus, PMT3 function requires the N-terminal sequence in addition to its promoter, whereas the PMT1 function is defined by the promoter.

The importance of Arabidopsis PHOSPHOLIPID N-METHYLTRANSFERASE in glycerolipid metabolism and plant growth.

Phosphatidylcholine (PC) is a major class of phospholipids that are essential for post-embryonic growth in plants. In Arabidopsis, three copies of the phospho-base N-methyltransferase, PMT1, PMT2, and PMT3, are known to account for PC biosynthesis because the triple-knockout mutant is devoid of biosynthesis and shows lethality in post-embryonic but not embryonic growth. Arabidopsis also contains a distinct phospholipid N-methyltransferase (PLMT) that is homologous with yeast and animal PLMT that methylates phospholipids to produce PC. However, the knockout mutant of PLMT does not show morphological phenotypes or decreased PC content, so the role of PLMT remains unclear. Here, we show that PLMT is ubiquitously expressed in different organs and localized at the endoplasmic reticulum, where PC is produced. Overexpression of PLMT in planta increased the content of phospholipids including PC and affected vegetative but not reproductive growth. Although silique lengths were shorter, pollen remained viable and mature seeds were produced. Intriguingly, seed triacylglycerol content was increased with altered fatty acid composition. We conclude that PLMT might be a functional enzyme in PC biosynthesis and play an organ-specific role in developing seeds, where rapid accumulation of triacylglycerol dominates the entire glycerolipid metabolic flux.

A Conserved Helix in the C-Terminal Region of Watermelon Silver Mottle Virus Nonstructural Protein S Is Imperative For Protein Stability Affecting Self-Interaction, RNA Silencing Suppression, and Pathogenicity.

In orthotospovirus, the nonstructural protein S (NSs) is the RNA-silencing suppressor (RSS) and pathogenicity determinant. Here, we demonstrate that a putative α-helix, designated H8, spanning amino acids 338 to 369 of the C-terminal region of the NSs protein, is crucial for self-interaction of watermelon silver mottle virus NSs protein and that the H8 affects RSS function. Co-immunoprecipitation, yeast two-hybrid, and bimolecular fluorescence complementation analyses revealed that the triple point mutation (TPM) of H8 amino acids Y338A, H350A, and F353A resulted in NSs protein self-interaction dysfunction. Transient expression of H8-deleted (ΔH8) and TPM NSs proteins in Nicotiana benthamiana plants by agroinfitration indicated that these proteins have weaker RSS activity and are far less stable than wild-type (WT) NSs. However, an electrophoretic mobility assay revealed that small interfering RNA (siRNA) binding ability of TPM NSs protein is not compromised. The pathogenicity assay of WT NSs protein expressed by the attenuated turnip mosaic virus vector restored severe symptoms in recombinant-infected N. benthamiana plants but not for ΔH8 or TPM proteins. Taken together, we conclude that the H8 helix in the C-terminal region of NSs protein is crucial for stabilizing NSs protein through self-interaction to maintain normal functions of RSS and pathogenicity, but not for NSs-siRNA binding activity.

The hidden depths of zebrafish skin.

Single-cell transcriptome analysis of zebrafish cells clarifies the signalling pathways controlling skin formation and reveals that some cells produce proteins required for human teeth to acquire their enamel.

Modification of the N-terminal FWKG-αH1 element of potyviral HC-Pro affects its multiple functions and generates effective attenuated mutants for cross-protection.

Control of plant viruses by cross-protection is limited by the availability of effective protective strains. Incorporation of an NIa-protease processing site in the extreme N-terminal region of the helper component protease (HC-Pro) of turnip mosaic virus (TuMV) resulted in a mutant virus TuHND I that induced highly attenuated symptoms. Recombination analysis verified that two variations, F7I mutation and amino acid 7-upstream-deletion, in HC-Pro co-determined TuHND I attenuation. TuHND I provided complete protection to Nicotiana benthamiana and Brassica campestris subsp. chinensis plants against infection by the severe parental strain. Aphid transmission tests revealed that TuHND I was not aphid-transmissible. An RNA silencing suppression (RSS) assay by agroinfiltration suggested the RSS-defective nature of the mutant HC-Pro. In the context (amino acids 3-17) encompassing the two variations of HC-Pro, we uncovered an FWKG-α-helix 1 (αH1) element that influenced the functions of aphid transmission and RSS, whose motifs were located far downstream. We further demonstrated that HC-Pro F7 was a critical residue on αH1 for HC-Pro functions and that reinstating αH1 in the RSS-defective HC-Pro of TuHND I restored the protein's RSS function. Yeast two-hybrid and bimolecular fluorescence complementation assays indicated the FWKG-αH1 element as an integral part of the HC-Pro self-interaction domain. The possibility of regulation of the mechanistically independent functions of RSS and aphid transmission by the FWKG-αH1 element is discussed. Extension of TuMV HC-Pro FWKG-αH1 variations to another potyvirus, zucchini yellow mosaic virus, also generated nonaphid-transmissible cross-protective mutant viruses. Hence, the modification of the FWKG-αH1 element can generate effective attenuated viruses for the control of potyviruses by cross-protection.

Baicalin inhibits APEC-induced lung injury by regulating gut microbiota and SCFA production.

Baicalin is a plant-derived flavonoid from Scutellaria baicalensis Georgi with multiple bioactivities and has a protective effect against avian pathogenic Escherichia coli (APEC) infection. However, the underlying mechanism of baicalin against APEC infection is still unknown. Therefore, we aimed to explore whether the protective effects and mechanisms of baicalin on APEC-induced lung inflammation were related to the regulation of gut microbiota. The results showed that baicalin significantly reduced APEC colonization and pro-inflammatory cytokines production, and additionally recovered air-blood barrier integrity in the lungs after APEC challenge. However, depletion of gut microbiota significantly weakened the protective effects of baicalin against APEC infection as mentioned above. Furthermore, baicalin markedly restored the dysbiosis of gut microbiota induced by APEC as well as increased the abundance of short chain fatty acid (SCFA)-producing bacteria and the production of SCFAs including acetic acid, propionic acid and butyric acid, especially acetic acid. In addition, the concentrations of acetic acid and its receptor free fatty acid receptor 2 (FFAR2) were significantly upregulated in the lung tissues after baicalin treatment. In conclusion, gut microbiota played a key role in the pharmacological action of baicalin against APEC-induced lung inflammation. Baicalin remodeled the dysbiosis of gut microbiota caused by APEC and increased the production of SCFAs, especially acetic acid in the gut, and then the increased acetate may circulate to the lungs to activate FFAR2 to defend APEC infection. Together, our study suggested that baicalin inhibited APEC infection through remodeling the gut microbiota dysbiosis and increasing the SCFA production. Furthermore, baicalin may serve as an alternative antibiotic and a novel therapeutic drug to prevent or treat APEC infection.

Mutation of histone H3 serine 86 disrupts GATA factor Ams2 expression and precise chromosome segregation in fission yeast.

Eukaryotic genomes are packed into discrete units, referred to as nucleosomes, by organizing around scaffolding histone proteins. The interplay between these histones and the DNA can dynamically regulate the function of the chromosomal domain. Here, we interrogated the function of a pair of juxtaposing serine residues (S86 and S87) that reside within the histone fold of histone H3. We show that fission yeast cells expressing a mutant histone H3 disrupted at S86 and S87 (hht2-S86AS87A) exhibited unequal chromosome segregation, disrupted transcriptional silencing of centromeric chromatin, and reduced expression of Ams2, a GATA-factor that regulates localization of the centromere-specific histone H3 variant CENP-A. We found that overexpression of ams2(+) could suppress the chromosome missegregation phenotype that arose in the hht2-S86AS87A mutant. We further demonstrate that centromeric localization of SpCENP-A(cnp1-1) was significantly compromised in hht2-S86AS87A, suggesting synergism between histone H3 and the centromere-targeting domain of SpCENP-A. Taken together, our work presents evidence for an uncharacterized serine residue in fission yeast histone H3 that affects centromeric integrity via regulating the expression of the SpCENP-A-localizing Ams2 protein. [173/200 words].