Effect of Non-homogeneous Mixing and Asymptomatic Individuals on Final Epidemic Size and Basic Reproduction Number in a Meta-Population Model.

To uncover the effective interventions during the pandemic period, a novel mathematical model, which incorporates separate compartments for incubation and asymptomatic individuals, has been developed in this paper. On the basis of a general mixing, final size relation and next-generation matrix are derived for a meta-population model by introducing the matrix blocking. The final size ([Formula: see text]) and the basic reproduction number ([Formula: see text]) are no longer a simple monotonous relationship. The analytical results of heterogeneity illustrate that activity is more sensitive than the others. And the proportion of asymptomatic individuals is a key factor for final epidemic size compared to the regulatory factor. Furthermore, the impact of preferential contact level on [Formula: see text] and [Formula: see text] is comparatively complex. The isolation can effectively reduce the final size, which further verifies its effectiveness. When vaccination is considered, the mixing methods maybe influence the doses of vaccination used and its effective. Moreover, using the present predictive model, we can provide the valuable reference about identifying the ideal strategies to curb the pandemic disease.

High D-arabitol production with osmotic pressure control fed-batch fermentation by Yarrowia lipolytica and proteomic analysis under nitrogen source perturbation.

D-arabitol, a five-carbon sugar alcohol, is widely used in food and pharmacy industry as a lower calorie sweetener or intermediate. Appropriate osmotic pressure was confirmed to facilitate polyol production by an osmophilic yeast strain of Yarrowia lipolytica with glycerol. In this study, an osmotic pressure control fed-batch fermentation strategy was used for high D-arabitol producing by Y. lipolytica ARA9 with crude glycerol. Glycerol was added to the broth quantitatively not only as a substrate but also as an osmotic agent. Meanwhile, NH3·H2O was fed as a nitrogen source and pH regulator. The maximum D-arabitol production reached 118.5 g/L at 108 h with the yield of 0.49 g/g and productivity of 1.10 g/L/h, respectively. Furthermore, a comparative proteomic analysis was used to study the cellular responses under excess and deficient nitrogen sources. Thirty-one differentially expressed protein spots belonging to seven different biological processes were identified. Excess nitrogen source enhanced gluconeogenesis and pentose phosphate pathways, both of which were involved in arabitol synthesis. In addition, cell growth was facilitated by increased expression of nucleotide and structural proteins. Enhanced energy and NADPH biosynthesis were employed to create a reductive environment and quell reactive oxygen species, improving D-arabitol production. Nitrogen deficiency resulted in cell rescue and stress response mechanisms such as reactive oxygen species elimination and heat shock protein response. The identified differentially expressed proteins provide information to reveal the mechanisms of the cellular responses under nitrogen source perturbation, and also provide guidance to improve D-arabitol production in metabolic engineering or process optimization methodologies.

Free fatty acids induce the demethylation of the fructose 1,6-biphosphatase 2 gene promoter and potentiate its expression in hepatocytes.

Obesity is a serious health issue as it is a social burden and the main risk factor for other metabolic diseases. Increasing evidence indicates that a high-fat diet (HFD) is the key factor for the development of obesity, but the key genes and their associated molecular mechanisms are still not fully understood. In this study, we performed integrated bioinformatic analysis and identified that fructose-1,6 biphosphatase 2 (FBP2) was involved in free fatty acids (FFAs)-induced lipid droplet accumulation in hepatocytes and HFD-induced obesity in mice. Our data showed that palmitate (PA) and oleic acid (OA) induced the expression of FBP2 in time- and dose-dependent manners, and accelerated the development of lipid droplets in LO2 human normal liver cells. In HFD-fed C57BL/6 mice, accompanied by insulin resistance and lipid droplet accumulation, the mRNA and protein levels of FBP2 in the livers also increased significantly. The results from the methylation sequencing PCR (MSP) and bisulfite specific PCR (BSP) indicated that PA/OA induced the demethylation of the FBP2 gene promoter in LO2 cells. Moreover, betaine, a methyl donor, attenuated the expression of the FBP2 gene, the accumulation of lipid droplets, and the expression of perilipin-2, a biomarker of lipid droplets, in LO2 cells. All these findings revealed that FBP2 might be involved in HFD-induced obesity, and it is of interest to investigate the role of FBP2 in the treatment and prevention of obesity and its associated complications.

Trilobatin ameliorates insulin resistance through IRS-AKT-GLUT4 signaling pathway in C2C12 myotubes and ob/ob mice.

BACKGROUND: Trilobatin, a natural compound, has been found to exhibit anti-diabetic properties in high-fat diet (HFD) and streptozotocin (STZ) induced type 2 diabetic mice. But up to now no research has been reported on the effect of trilobatin on insulin resistance in peripheral tissues. Herein, we determined the effects of trilobatin on insulin resistance in palmitate-treated C2C12 myotubes and ob/ob mice. METHODS: Male ob/ob mice (8-10 weeks) and same background C57BL/6 mice were used to evaluate the role of trilobatin on insulin resistance; protein expression and phosphorylation were measured by western blot; glucose uptake was determined a fluorescent test. RESULTS: Treatment with trilobatin prevented palmitate-induced insulin resistance by enhancing glucose uptake and the phosphorylation of insulin resistance substrate 1 (IRS1) and protein Kinase B, (PKB/AKT), recovered the translocation of GLUT4 from cytoplasm to membrane, but preincubation with LY294002, an inhibitor of PI3K, blocked the effects of trilobatin on glucose uptake and the distribution of GLUT4 in C2C12 myotubes. Furthermore, administration with trilobatin for 4 weeks significantly improved insulin resistance by decreasing fasting blood glucose and insulin in serum, enhancing the phosphorylation of IRS1 and AKT, and recovering the expression and translocation of GLUT4 in ob/ob mice. CONCLUSIONS: IRS-AKT-GLUT4 signaling pathway might be involved in trilobatin ameliorating insulin resistance in skeletal muscle of obese animal models.

SmbHLH53 is relevant to jasmonate signaling and plays dual roles in regulating the genes for enzymes in the pathway for salvianolic acid B biosynthesis in Salvia miltiorrhiza.

Basic helix-loop-helix (bHLH) transcription factors play essential roles in myriad regulatory processes, including secondary metabolism. In this study with Salvia miltiorrhiza, we isolated and characterized SmbHLH53, which encodes a bHLH family member. Expression of this gene was significantly induced by wounding and multiple hormones, including methyl jasmonic acid; transcript levels were highest in the leaves and roots. Phylogenetic analysis indicated that SmbHLH53 clusters withAtbHLH17 and AtbHLH13, two negative regulators of jasmonate (JA) responses, and is localized in the nucleus and cell membrane. Yeast two-hybrid and bimolecular fluorescent complementation assays indicated that SmbHLH53 forms a homodimer as well as a heterodimer with SmbHLH37. It also interacts with both SmJAZs1/3/8 and SmMYC2, the core members of the JA signal pathway. Unexpectedly, we noted that overexpression of SmbHLH53 did not significantly influence the concentrations of rosmarinic acid and salvianolic acid B in transgenic plants. Results from yeast one-hybrid assays showed that SmbHLH53 binds to the promoters of SmTAT1, SmPAL1, and Sm4CL9, the key genes for enzymes in the pathway for phenolic acid synthesis. Assays of transient transcriptional activity demonstrated that SmbHLH53 represses the promoter of SmTAT1 while activating the promoter of Sm4CL9. Thus, the present work revealed that SmbHLH53 may play dual roles in regulating the genes for enzymes in the pathway for Sal B biosynthesis.

Trilobatin, a Novel SGLT1/2 Inhibitor, Selectively Induces the Proliferation of Human Hepatoblastoma Cells.

Studies have indicated that Na+-d-glucose co-transporter (SGLT) inhibitors had anti-proliferative activity by attenuating the uptake of glucose in several tumor cell lines. In this study, the molecular docking showed that, trilobatin, one of the dihydrochalcones from leaves of Lithocarpus polystachyus Rehd., might be a novel inhibitor of SGLT1 and SGLT2, which evidently attenuated the uptake of glucose in vitro and in vivo. To our surprise, we observed that trilobatin did not inhibit, but promoted the proliferation of human hepatoblastoma HepG2 and Huh 7 cells when it was present at high concentrations. At the same time, incubation with high concentrations of trilobatin arrested the cell cycle at S phase in HepG2 cells. We also found that treatment with trilobatin had no significant effect on the expression of hepatitis B x-interacting protein (HBXIP) and hepatocyte nuclear factor (HNF)-4α, the two key regulators of hepatocyte proliferation. Taken together, although trilobatin worked as a novel inhibitor of SGLTs to attenuate the uptake of glucose, it also selectively induced the cell proliferation of HepG2 cells, suggesting that not all the SGLT inhibitors inhibited the proliferation of tumor cells, and further studies are needed to assess the anti-cancer potentials of new glucose-lowering agents.

AtPAP1 Interacts With and Activates SmbHLH51, a Positive Regulator to Phenolic Acids Biosynthesis in Salvia miltiorrhiza.

Phenolic acids from Salvia miltiorrhiza have drawn considerable attention in recent years because of their remarkable pharmacological activities. We previously reported that Arabidopsis thaliana transcription factor production of anthocyanin pigment 1 (AtPAP1) has strong capability to promote the production of phenolic acids in S. miltiorrhiza. However, the responsible molecular mechanism is unclear. Here, we analyzed the transcriptome of transgenic S. miltiorrhiza that over-expressed AtPAP1. Transcriptome analysis revealed 4,152 genes that were differentially expressed due to ectopic AtPAP1 overexpression. SmbHLH51, a novel bHLH gene significantly up-regulated by constitutive expression of AtPAP1, was isolated from S. miltiorrhiza for detailed functional characterization. SmbHLH51 localizes in the nuclei and interacts with AtPAP1, indicating that they probably comprise a regulatory transcription complex. Enhanced or reduced expression of SmbHLH51 was achieved in S. miltiorrhiza by gain- or loss-of-function assays, respectively, revealing that SmbHLH51 is a positive transcriptional regulator of the pathway for phenolic acid biosynthesis. We propose that applying this functional genomics approach through the transcriptomic analyses is an efficient means for identifying novel genes involved in plant secondary metabolism.

SmMYB111 Is a Key Factor to Phenolic Acid Biosynthesis and Interacts with Both SmTTG1 and SmbHLH51 in Salvia miltiorrhiza.

Transcription factors that include myeloblastosis (MYB), basic helix-loop-helix (bHLH), and tryptophan-aspartic acid (WD)-repeat protein often form a ternary complex to regulate the phenylpropanoid pathway. However, only a few MYB and bHLH members involved in the biosynthesis of salvianolic acid B (Sal B) have been reported, and little is known about Sal B pathway regulation by the WD40 protein transparent testa glabra 1 (TTG1)-dependent transcriptional complexes in Salvia miltiorrhiza. We isolated SmTTG1 from that species for detailed functional characterization. Enhanced or reduced expression of SmTTG1 was achieved by gain- or loss-of-function assays, respectively, revealing that SmTTG1 is necessary for Sal B biosynthesis. Interaction partners of the SmTTG1 protein were screened by yeast two-hybrid (Y2H) assays with the cDNA library of S. miltiorrhiza. A new R2R3-MYB transcription factor, SmMYB111, was found through this screening. Transgenic plants overexpressing or showing reduced expression of SmMYB111 upregulated or deregulated, respectively, the yields of Sal B. Both Y2H and bimolecular fluorescent complementation experiments demonstrated that SmMYB111 interacts with SmTTG1 and SmbHLH51, a positive regulator of the phenolic acid pathway. Our data verified the function of SmTTG1 and SmMYB111 in regulating phenolic acid biosynthesis in S. miltiorrhiza. Furthermore, ours is the first report of the potential ternary transcription complex SmTTG1-SmMYB111-SmbHLH51, which is involved in the production of Sal B in that species.

SmLEA2, a gene for late embryogenesis abundant protein isolated from Salvia miltiorrhiza, confers tolerance to drought and salt stress in Escherichia coli and S. miltiorrhiza.

Abiotic stresses, such as drought and high salinity, are major factors that limit plant growth and productivity. Late embryogenesis abundant (LEA) proteins are members of a diverse, multigene family closely associated with tolerance to abiotic stresses in numerous organisms. We examined the function of SmLEA2, previously isolated from Salvia miltiorrhiza, in defense responses to drought and high salinity. Phylogenetic analysis indicated that SmLEA2 belongs to the LEA_2 subfamily. Its overexpression in Escherichia coli improved growth performance when compared with the control under salt and drought stresses. We further characterized its roles in S. miltiorrhiza through overexpression and RNAi-mediated silencing. In response to drought and salinity treatments, transgenic plants overexpressing SmLEA2 exhibited significantly increased superoxide dismutase activity, reduced levels of lipid peroxidation, and more vigorous growth than empty-vector control plants did. However, transgenic lines in which expression was suppressed showed the opposite results. Our data demonstrate that SmLEA2 plays an important role in the abiotic stress response and its overexpression in transgenic S. miltiorrhiza improves tolerance to excess salt and drought conditions.

Combination of transcriptomic and metabolomic analyses reveals a JAZ repressor in the jasmonate signaling pathway of Salvia miltiorrhiza.

Jasmonates (JAs) are plant-specific key signaling molecules that respond to various stimuli and are involved in the synthesis of secondary metabolites. However, little is known about the JA signal pathway, especially in economically significant medicinal plants. To determine the functions of novel genes that participate in the JA-mediated accumulation of secondary metabolites, we examined the metabolomic and transcriptomic signatures from Salvia miltiorrhiza. For the metabolome, 35 representative metabolites showing significant changes in rates of accumulation were extracted and identified. We also screened out 2131 differentially expressed unigenes, of which 30 were involeved in the phenolic secondary metabolic pathway, while 25 were in the JA biosynthesis and signal pathways. Among several MeJA-induced novel genes, SmJAZ8 was selected for detailed functional analysis. Transgenic plants over-expressing SmJAZ8 exhibited a JA-insensitive phenotype, suggesting that the gene is a transcriptional regulator in the JA signal pathway of S. miltiorrhiza. Furthermore, this transgenic tool revealed that JAZ genes have novel function in the constitutive accumulation of secondary metabolites. Based on these findings, we propose that the combined strategy of transcriptomic and metabolomic analyses is valuable for efficient discovery of novel genes in plants.

Overexpression of SmLEA enhances salt and drought tolerance in Escherichia coli and Salvia miltiorrhiza.

Salinity and drought are important abiotic stresses limiting plant growth and development. Late embryogenesis abundant (LEA) proteins are a group of proteins associated with tolerance to water-related stress. We previously cloned an LEA gene, SmLEA, from Salvia miltiorrhiza Bunge. Phylogenetic analysis indicated that SmLEA belongs to Group LEA14, which is involved in the dehydration response. To determine its function in detail, we have now overexpressed SmLEA in Escherichia coli and S. miltiorrhiza. The logarithmic increase in accumulations of SmLEA proteins in E. coli occurred earlier under salinity than under standard conditions. SmLEA-transformed S. miltiorrhiza plants also showed faster root elongation and a lower malondialdehyde concentration than the empty vector control plants did when cultured on MS media supplemented with 60 mM NaCl or 150 mM mannitol. Moreover, SmLEA-overexpressing transgenics experienced a less rapid rate of water loss. Under either salinity or drought, overexpressing plants had greater superoxide dismutase activity and a higher glutathione concentration. These results suggest that SmLEA may be useful in efforts to improve drought and salinity tolerance in S. miltiorrhiza. Our data also provide a good foundation for further studies into the stress resistance mechanism and molecular breeding of this valuable medicinal plant.

Pathway engineering for phenolic acid accumulations in Salvia miltiorrhiza by combinational genetic manipulation.

To produce beneficial phenolic acids for medical and commercial purposes, researchers are interested in improving the normally low levels of salvianolic acid B (Sal B) produced by Salvia miltiorrhiza. Here, we present a strategy of combinational genetic manipulation to enrich the precursors available for Sal B biosynthesis. This approach, involving the lignin pathway, requires simultaneous, ectopic expression of an Arabidopsis Production of Anthocyanin Pigment 1 transcription factor (AtPAP1) plus co-suppression of two endogenous, key enzyme genes: cinnamoyl-CoA reductase (SmCCR) and caffeic acid O-methyltransferase (SmCOMT). Compared with the untransformed control, we achieved a greater accumulation of Sal B (up to 3-fold higher) along with a reduced lignin concentration. This high-Sal B phenotype was stable in roots during vegetative growth and was closely correlated with increased antioxidant capacity for the corresponding plant extracts. Although no outward change in phenotype was apparent, we characterized the molecular phenotype through integrated analysis of transcriptome and metabolome profiling. Our results demonstrated the far-reaching consequences of phenolic pathway perturbations on carbohydrate metabolism, respiration, photo-respiration, and stress responses. This report is the first to describe the production of valuable end products through combinational genetic manipulation in S. miltiorrhiza plants. Our strategy will be effective in efforts to metabolically engineer multi-branch pathway(s), such as the phenylpropanoid pathway, in economically significant medicinal plants.