Transcriptomics Profiling of Acer pseudosieboldianum Molecular Mechanism against Freezing Stress.

Low temperature is an important environmental factor that affects the growth and development of trees and leads to the introduction of failure in the genetic improvement of trees. Acer pseudosieboldianum is a tree species that is well-known for its bright red autumn leaf color. These trees are widely used in landscaping in northeast China. However, due to their poor cold resistance, introduced A. pseudosieboldianum trees suffer severe freezing injury in many introduced environments. To elucidate the physiological indicators and molecular mechanisms associated with freezing damage, we analyzed the physiological indicators and transcriptome of A. pseudosieboldianum, using kits and RNA-Seq technology. The mechanism of A. pseudosieboldianum in response to freezing stress is an important scientific question. In this study, we used the shoots of four-year-old A. pseudosieboldianum twig seedlings, and the physiological index and the transcriptome of A. pseudosieboldianum under low temperature stress were investigated. The results showed that more than 20,000 genes were detected in A. pseudosieboldianum under low temperature (4 °C) and freezing temperatures (-10 °C, -20 °C, -30 °C, and -40 °C). There were 2505, 6021, 5125, and 3191 differential genes (DEGs) between -10 °C, -20°C, -30°C, -40 °C, and CK (4 °C), respectively. Among these differential genes, 48 genes are involved in the MAPK pathway and 533 genes are involved in the glucose metabolism pathway. In addition, the important transcription factors (MYB, AP2/ERF, and WRKY) involved in freezing stress were activated under different degrees of freezing stress. A total of 10 sets of physiological indicators of A. pseudosieboldianum were examined, including the activities of five enzymes and the accumulation of five hormones. All of the physiological indicators except SOD and GSH-Px reached their maximum values at -30 °C. The enzyme activity of SOD was highest at -10 °C, and that of GSH-Px was highest at -20 °C. Our study is the first to provide a more comprehensive understanding of the differential genes (DEGs) involved in A. pseudosieboldianum under freezing stress at different temperatures at the transcriptome level. These results may help to clarify the molecular mechanism of cold tolerance of A. pseudosieboldianum and provide new insights and candidate genes for the genetic improvement of the freezing tolerance of A. pseudosieboldianum.

Anti-inflammatory, antioxidant and anti-virulence roles of atractylodin in attenuating Listeria monocytogenes infection.

Background: Listeria monocytogenes (L. monocytogenes), as a pandemic foodborne pathogen, severely threatens food security and public health care worldwide, which evolves multiple bacterial virulence factors (such as listeriolysin O, LLO) for manipulating the immune response of L. monocytogenes-host interactions. Methods: Hemolysis assay was employed to screen a potential LLO inhibitor and the underlying mechanisms were investigated using molecular dynamics (MD) simulation and oligomerization assay. The effects of candidates on immune response were examined by qRT-PCR and immunoblotting analysis. Histological analysis, ELISA assay and biochemistry detection were conducted to assess in vivo efficacy of candidates. Results: In the present study, natural terpenoid atractylodin was characterized as an alternative drug candidate for the treatment of L. monocytogenes by the regulation of LLO function and host Nrf2/NLRP3 signaling pathway. Notably, in vivo infection model by L. monocytogenes also highlighted that atractylodin treatment provided effective therapeutic benefits, as evidenced by decreased bacterial burden and diminished inflammation. Congruently, the survival rate of L. monocytogenes-infection mice increased significantly from 10.0% to 40.0% by atractylodin treatment. Conclusion: Collectively, our study showed for the first time that atractylodin has tremendous potential to attenuate L. monocytogenes pathogenicity by blocking LLO pore formation and mediating the suppression of inflammation and oxidative stress, providing a promising therapeutic strategy and broadening the applications of atractylodin against L. monocytogenes infection.

Variations in Growth and Photosynthetic Traits of Polyploid Poplar Hybrids and Clones in Northeast China.

To evaluate differences among 19 different ploidy hybrid poplar clones grown in northeast China, 21 traits related to growth traits and photosynthetic characteristics were detected and analyzed. Abundant phenotypic variations exist among and within populations, and these variations are the basis of forest tree genetic improvements. In this research, variance analysis showed that the traits except the net photosynthesis rate among the different ploidies and all the other traits exhibited significant differences among the ploidies or clones (p < 0.01). Estimation of phenotypic coefficients of variation, genotypic coefficients of variation, and repeatability is important for selecting superior materials. The larger the value, the greater the potential for material selection improvement. The repeatability of the different traits ranged from 0.88 to 0.99. The phenotypic and genotypic coefficients of variation of all the investigated traits ranged from 6.88% to 57.40% and from 4.85% to 42.89%, respectively. Correlation analysis showed that there were significant positive correlations between tree height, diameter, and volume. Transpiration rate, intercellular carbon dioxide concentration, and stomatal conductance were significantly positively correlated with each other but negatively correlated with instantaneous water use efficiency. Growth traits were weakly correlated with photosynthetic indexes. The rank correlation coefficient showed that most of the growth indicators reached a significant correlation level among different years (0.40-0.98), except 1-year-old tree height with 4-year-old tree height and 1-year-old ground diameter with 3-year-old tree height, which indicated the potential possibility for early selection of elite clones. Principal analysis results showed that the contribution rate of the first principal component was 46.606%, and 2-year-old tree height, 2-year-old ground diameter, 3-year-old tree height, 3-year-old ground diameter, 3-year-old diameter at breast height, 3-year-old volume, 4-year-old tree height, 4-year-old ground diameter, 4-year-old diameter at breast height, and 4-year-old volume showed higher vector values than other traits. With the method of multiple-trait comprehensive evaluation to evaluate clones, SX3.1, SY3.1, and XY4.2 were selected as elite clones, and the genetic gains of height, basal diameter, diameter at breast height, and volume of selected clones ranged from 12.85% to 64.87% in the fourth growth year. The results showed fundamental information for selecting superior poplar clones, which might provide new materials for the regeneration and improvement of forests in Northeast China.

Metallo-ß-lactamases inhibitor fisetin attenuates meropenem resistance in NDM-1-producing Escherichia coli.

The prevalence and development of New Delhi metallo-ß-lactamase-1 (NDM-1) have led to increases in bacterial resistance to the majority of clinically used antibiotics, including carbapenems. This study attempts to identify a novel inhibitor of NDM-1 for resistant bacteria infection. Herein, we found that fisetin, as an agent, distinctly inhibits the activity of NDM-1 (IC50 = 9.68 µg/mL) through on enzyme activity inhibition screening. Notably, fisetin is a metallo-ß-lactamases inhibitor without the ability to chelate zinc ions, as well as with a significantly inhibitory effect on NDM-9, VIM-1, IMP-1 and KPC-2. The combination of fisetin with meropenem could attenuate meropenem resistance in NDM-1-positive Escherichia coli. The MIC values of combined treatment were lower than those found for meropenem or fisetin alone (FICI from 0.25 ± 0.00 to 0.38 ± 0.00) although fisetin lacks antibacterial activities (MIC＞1024 µg/mL). Furthermore, fisetin combined with meropenem could kill all tested bacteria no more than 3 h in vitro and this synergistic effect could also be observed in vivo. Molecular dynamics simulations revealed that fisetin successfully inhibit the hydrolytic activity of NDM-1. Additionally, the mutation of NDM-1 resulted in a decreased inhibition of NDM-1 activity by fisetin compared with the WT protein. Finally, our results indicate that fisetin is an effective NDM-1 inhibitor, which suggests the combination of this compound with meropenem is a promising strategy for carbapenem-resistant bacterial infection.

Inhibitory effect of hederagenin on Streptococcus pneumoniae pneumolysin in vitro.

Streptococcus pneumoniae is an important pathogen that causes otitis media, pneumonia, meningitis and bacteremia. As an important virulence factors of S. pneumoniae, pneumolysin (PLY) can penetrate cell membranes and lead to cell lysis and inflammation, which is one of the main causes of infection and damage of S. pneumoniae. Therefore, using pneumolysin as a target to study its inhibitors can provide a new treatment strategy for pneumococcal disease. This study analyzed the inhibitory effect of the natural compound hederagenin on PLY in vitro. The results show that hederagenin has great potential as a new strategy for the treatment of pneumococcal diseases.

Acacetin Alleviates Listeria monocytogenes Virulence Both In Vitro and In Vivo via the Inhibition of Listeriolysin O.

Listeria monocytogenes is a ubiquitous Gram-positive foodborne pathogen that is responsible for listeriosis in both humans and several animal species. The bacterium secretes a pore-forming cholesterol-dependent cytolysin, listeriolysin O (LLO), a major virulence factor involved in the activation of cellular processes. The ability of LLO to lyse erythrocytes is a measure of LLO activity. We used hemolytic activity assay to screen the LLO inhibitors. Acacetin was found to be an LLO inhibitor, which is a di-hydroxy and mono-methoxy flavone present in various plants, including Black locust, Damiana, and Silver birch. As the features of acacetin are of low toxicity and have less acquired resistance, it comes to a hotspot in drug development. In our study, we report that acacetin antagonized the hemolytic activity of L. monocytogenes culture supernatants and purified LLO by directly interfering with the formation of oligomers without inhibiting the bacterial growth and the expression of LLO. Acacetin also relieved the injury of alveolar epithelial cells by inhibiting LLO activity. Further, acacetin significantly promoted the clearance of L. monocytogenes and alleviated the histopathological damage, thereby raising survival rate, which conferred mice with effective protection against L. monocytogenes infection. Using molecular docking and dynamics simulation, we further proved the mechanism of acacetin antagonizing LLO pore-forming activity by direct binding to the second membrane-inserting helix bundle (HB2) of LLO domain 3. These data suggested that acacetin recedes the virulence of L. monocytogenes both in vivo and in vitro, and this study provided a promising candidate and potential alternative for the prevention and treatment of L. monocytogenes infections.

MicroRNA-375: potential cancer suppressor and therapeutic drug.

MiR-375 is a conserved noncoding RNA that is known to be involved in tumor cell proliferation, migration, and drug resistance. Previous studies have shown that miR-375 affects the epithelial-mesenchymal transition (EMT) of human tumor cells via some key transcription factors, such as Yes-associated protein 1 (YAP1), Specificity protein 1 (SP1) and signaling pathways (Wnt signaling pathway, nuclear factor κB (NF-κB) pathway and transforming growth factor ß (TGF-ß) signaling pathway) and is vital for the development of cancer. Additionally, recent studies have identified microRNA (miRNA) delivery system carriers for improved in vivo transportation of miR-375 to specific sites. Here, we discussed the role of miR-375 in different types of cancers, as well as molecular mechanisms, and analyzed the potential of miR-375 as a molecular biomarker and therapeutic target to improve the efficiency of clinical diagnosis of cancer.