梭梭根际枯草芽孢杆菌WM13-24对多年生黑麦草耐盐性的影响

以从梭梭根际分离得到的促生细菌枯草芽孢杆菌WM13-24为供试菌株,大肠杆菌DH5α和枯草芽孢杆菌GB03分别为阴性对照和阳性对照,研究WM13-24对多年生黑麦草耐盐性的影响。结果表明：1）在不同浓度NaCl处理（0,150和300 mmol/L）下,接种WM13-24提高了黑麦草的生物量、叶绿素含量、根长和根系活力。尤其是在150 mmol/L NaCl胁迫下,与空白对照相比,接种WM13-24处理的黑麦草植株叶绿素a和叶绿素b含量分别显著提高44.05%和53.79%,根长和根系活力分别显著提高69.21%和49.47%（P < 0.05）;300 mmol/L NaCl胁迫下,根长和根系活力分别显著提高24.07%和58.48%（P < 0.05）。2）不同浓度NaCl胁迫下,接种WM13-24提高了黑麦草的过氧化氢酶活性,降低了相对质膜透性和丙二醛含量。尤其是在300 mmol/L NaCl胁迫下,与空白对照相比,接种WM13-24显著提高黑麦草叶片过氧化氢酶活性64.21%,相对质膜透性和丙二醛含量分别显著降低了24.56%和54.24%（P < 0.05）。3）不同浓度NaCl胁迫下,接种根际有益细菌提高了黑麦草的可溶性糖和脯氨酸含量,降低了叶片渗透势,尤其在300 mmol/L NaCl胁迫下,与空白对照相比,接种WM13-24分别显著提高黑麦草叶片可溶性糖和脯氨酸含量84.41%和82.71%（P < 0.05）。4）接种根际有益细菌提高了在不同浓度NaCl胁迫下黑麦草地上部和根中的K⁺含量,降低了Na⁺含量,从而提高了K⁺/Na⁺比,尤其是在300 mmol/L NaCl胁迫下,与空白对照相比,接种WM13-24显著提高根中的K⁺/Na⁺比87.93%（P < 0.05）。本研究结果为利用荒漠植物根际促生细菌提高草类植物耐盐性和在盐碱地区建植牧草和草坪草奠定了一定的理论和实践基础。     

Transcriptome-Wide Identification and Expression Profiles of Masson Pine WRKY Transcription Factors in Response to Low Phosphorus Stress

Plant Molecular Biology Reporter - Masson pine (Pinus massoniana Lamb.) is an economically important conifer tree that can be widely used for timber, pulp, and resin production. However, the...     

Attenuation of CCl4-Induced Hepatic Fibrosis in Mice by Vaccinating against TGF-β1

Transforming growth factor β1 (TGF-β1) is the pivotal pro-fibrogenic cytokine in hepatic fibrosis. Reducing the over-produced expression of TGF-β1 or blocking its signaling pathways is considered to be a promising therapeutic strategy for hepatic fibrosis. In this study, we evaluated the feasibility of attenuating hepatic fibrosis by vaccination against TGF-β1 with TGF-β1 kinoids. Two TGF-β1 kinoid vaccines were prepared by cross-linking TGF-β1-derived polypeptides (TGF-β1²⁵–[41-65] and TGF-β1³⁰–[83-112]) to keyhole limpet hemocyanin (KLH). Immunization with the two TGF-β1 kinoids efficiently elicited the production of high-levels of TGF-β1-specific antibodies against in BALB/c mice as tested by enzyme-linked immunosorbent assay (ELISA) and Western blotting. The antisera neutralized TGF-β1-induced growth-inhibition on mink lung epithelial cells (Mv1Lu) and attenuated TGF-β1-induced Smad2/3 phosphorylation, α-SMA, collagen type 1 alpha 2 (COL1A2), plasminogen activator inhibitor-1 (PAI-1) and tissue inhibitor of metalloproteinase-1 (TIMP-1) expression in the rat hepatic stellate cell (HSC) line, HSC-T6. Vaccination against TGF-β1 with the kinoids significantly suppressed CCl₄-induced collagen deposition and the expression of α-SMA and desmin, attenuated hepatocyte apoptosis and accelerated hepatocyte proliferation in BALB/c mice. These results demonstrated that immunization with the TGF-β1 kinoids efficiently attenuated CCl₄-induced hepatic fibrosis and liver injury. Our study suggests that vaccination against TGF-β1 might be developed into a feasible therapeutic approach for the treatment of chronic fibrotic liver diseases.     

Engineered short branched-chain acyl-CoA synthesis in E. coli and acylation of chloramphenicol to branched-chain derivatives

Short branched-chain acyl-CoAs are important building blocks for a wide variety of pharmaceutically valuable natural products. Escherichia coli has been used as a heterologous host for the production of a variety of natural compounds for many years. In the current study, we engineered synthesis of isobutyryl-CoA and isovaleryl-CoA from glucose in E. coli by integration of the branched-chain α-keto acid dehydrogenase complex from Streptomyces avermitilis. In the presence of the chloramphenicol acetyltransferase (cat) gene, chloramphenicol was converted to both chloramphenicol-3-isobutyrate and chloramphenicol-3-isovalerate by the recombinant E. coli strains, which suggested successful synthesis of isobutyryl-CoA and isovaleryl-CoA. Furthermore, we improved the α-keto acid precursor supply by overexpressing the alsS gene from Bacillus subtilis and the ilvC and ilvD genes from E. coli and thus enhanced the synthesis of short branched-chain acyl-CoAs. By feeding 25 mg/L chloramphenicol, 2.96?±?0.06 mg/L chloramphenicol-3-isobutyrate and 3.94?±?0.06 mg/L chloramphenicol-3-isovalerate were generated by the engineered E. coli strain, which indicated efficient biosynthesis of short branched-chain acyl-CoAs. HPLC analysis showed that the most efficient E. coli strain produced 80.77?±?3.83 nmol/g wet weight isovaleryl-CoA. To our knowledge, this is the first report of production of short branched-chain acyl-CoAs in E. coli and opens a way to biosynthesize various valuable natural compounds based on these special building blocks from renewable carbon sources.     

Baicalein protects against doxorubicin-induced cardiotoxicity by attenuation of mitochondrial oxidant injury and JNK activation

The cardiotoxicity of doxorubicin limits its clinical use in the treatment of a variety of malignancies. Previous studies suggest that doxorubicin-associated cardiotoxicity is mediated by reactive oxygen species (ROS)-induced apoptosis. We therefore investigated if baicalein, a natural antioxidant component of Scutellaria baicalensis, could attenuate ROS generation and cell death induced by doxorubicin. Using an established chick cardiomyocyte model, doxorubicin (10 μM) increased cell death in a concentration- and time-dependent manner. ROS generation was increased in a dose-response fashion and associated with loss of mitochondrial membrane potential. Doxorubicin also augmented DNA fragmentation and increased the phosphorylation of ROS-sensitive pro-apoptotic kinase c-Jun N-terminal kinase (JNK). Adjunct treatment of baicalein (25 μM) and doxorubicin for 24 h significantly reduced both ROS generation (587 ± 89 a.u. vs. 932 a.u. ± 121 a.u., P < 0.01) and cell death (30.6 ± 5.1% vs. 46.8 ± 8.3%, P < 0.01). The dissipated mitochondrial potential and increased DNA fragmentation were also ameliorated. Along with the reduction of ROS and apoptosis, baicalein attenuated phosphorylation of JNK induced by doxorubicin (1.7 ± 0.3 vs. 3.0 ± 0.4-fold, P < 0.05). Co-treatment of cardiomyocytes with doxorubicin and JNK inhibitor SP600125 (10 μM; 24 h) reduced JNK phosphorylation and enhanced cell survival, suggesting that the baicalein protection against doxorubicin cardiotoxicity was mediated by JNK activation. Importantly, concurrent baicalein treatment did not interfere with the anti-proliferative effects of doxorubicin in human breast cancer MCF-7 cells. In conclusion, baicalein adjunct treatment confers anti-apoptotic protection against doxorubicin-induced cardiotoxicity without compromising its anti-cancer efficacy.     

MicroRNA-192 targeting retinoblastoma 1 inhibits cell proliferation and induces cell apoptosis in lung cancer cells

microRNAs play an important roles in cell growth, differentiation, proliferation and apoptosis. They can function either as tumor suppressors or oncogenes. We found that the overexpression of miR-192 inhibited cell proliferation in A549, H460 and 95D cells, and inhibited tumorigenesis in a nude mouse model. Both caspase-7 and the PARP protein were activated by the overexpression of miR-192, thus suggesting that miR-192 induces cell apoptosis through the caspase pathway. Further studies showed that retinoblastoma 1 (RB1) is a direct target of miR-192. Over-expression of miR-192 decreased RB1 mRNA and protein levels and repressed RB1-3'-UTR reporter activity. Knockdown of RB1 using siRNA resulted in a similar cell morphology as that observed for overexpression of miR-192. Additionally, RB1-siRNA treatment inhibited cell proliferation and induced cell apoptosis in lung cancer cells. Analysis of miRNA expression in clinical samples showed that miR-192 is significantly downregulated in lung cancer tissues compared to adjacent non-cancerous lung tissues. In conclusion, our results demonstrate that miR-192 is a tumor suppressor that can target the RB1 gene to inhibit cell proliferation and induce cell apoptosis in lung cancer cells. Furthermore, miR-192 was expressed at low levels in lung cancer samples, indicating that it might be a promising therapeutic target for lung cancer treatment.     

Renal proximal tubule angiotensin AT1A receptors regulate blood pressure

All components of the renin angiotensin system necessary for ANG II generation and action have been reported to be present in renal proximal convoluted tubules. Given the close relationship between renal sodium handling and blood pressure regulation, we hypothesized that modulating the action of ANG II specifically in the renal proximal tubules would alter the chronic level of blood pressure. To test this, we used a proximal tubule-specific, androgen-dependent, promoter construct (KAP2) to generate mice with either overexpression of a constitutively active angiotensin type 1A receptor transgene or depletion of endogenous angiotensin type 1A receptors. Androgen administration to female transgenic mice caused a robust induction of the transgene in the kidney and increased baseline blood pressure. In the receptor-depleted mice, androgen administration to females resulted in a Cre recombinase-mediated deletion of angiotensin type 1A receptors in the proximal tubule and reduced blood pressure. In contrast to the changes observed at baseline, there was no difference in the blood pressure response to a pressor dose of ANG II in either experimental model. These data, from two separate mouse models, provide evidence that ANG II signaling via the type 1A receptor in the renal proximal tubule is a regulator of systemic blood pressure under baseline conditions.     

一株灰肉红菇内生真菌的分离鉴定及其抑菌活性研究

灰肉红菇（Russula griseocarnosa）是岭南地区著名的野生食药用真菌。本研究通过组织分离的方法,从灰肉红菇子实体分离获得一株内生真菌,经形态学和分子生物学分析鉴定为爪哇虫草（Cordyceps javanica）。以牛津杯抑菌圈法及二倍稀释法测试了其菌丝体胞内和胞外多糖粗提物对金黄色葡萄球菌（Staphylococcus aureus）和铜绿假单胞菌（Pseudomonas aeruginosa）的抑菌活性。结果表明：水溶性胞内、胞外多糖对金黄色葡萄球菌及铜绿假单胞菌均具有抑菌活性,最低抑菌浓度（MIC）为37.5 mg/mL。     

Xylose‐fermenting Pichia stipitis by genome shuffling for improved ethanol production

Xylose fermentation is necessary for the bioconversion of lignocellulose to ethanol as fuel, but wild‐type Saccharomyces cerevisiae strains cannot fully metabolize xylose. Several efforts have been made to obtain microbial strains with enhanced xylose fermentation. However, xylose fermentation remains a serious challenge because of the complexity of lignocellulosic biomass hydrolysates. Genome shuffling has been widely used for the rapid improvement of industrially important microbial strains. After two rounds of genome shuffling, a genetically stable, high‐ethanol‐producing strain was obtained. Designated as TJ2‐3, this strain could ferment xylose and produce 1.5 times more ethanol than wild‐type Pichia stipitis after fermentation for 96 h. The acridine orange and propidium iodide uptake assays showed that the maintenance of yeast cell membrane integrity is important for ethanol fermentation. This study highlights the importance of genome shuffling in P. stipitis as an effective method for enhancing the productivity of industrial strains.