Trehalose protects wine yeast against oxidation under thermal stress

Accumulation of trehalose in yeasts has been suggested to be an important mechanism of tolerance against adverse stress conditions, particularly in thermal stress. However, under thermal stress, it is not clear if the mechanism of protection is related to its antioxidant role. In this study, a newly isolated wine yeast Saccharomyces cerevisia was used to examine the protective effect of trehalose against oxidation during thermal stress treatment. Cells were treated either with a mild heat treatment at 37°C (which leads to trehalose accumulation) or with a 50 mM trehalose solution and then exposed to a high temperature of 53°C. According to our results, mild heat treatment at 37°C and trehalose addition which promote accumulation of trehalose significantly increased cell survival upon exposure to thermal stress at 53°C which seems to be correlated with decrease in reactive oxygen species levels and lipid peroxidation. Trehalose could protect yeast from oxidative injuries under thermal stress.     

Rapid functional divergence of a newly evolved polyubiquitin gene in Drosophila and its role in the trade-off between male fecundity and lifespan

The cost of reproduction is a pivotal trade-off with various biological processes during the evolution of organisms. However, the genes and molecular mechanisms underlying the evolution of balancing reproductive capacity and its cost are still largely unknown. Here, we present a comprehensive study on the evolution, expression, and biological functions of a newly evolved pair of X-linked polyubiquitin tandemly duplicated genes, CG32744 and CG11700, of which the duplication event occurred in Drosophila melanogaster lineage after the split from D. simulans clade. We found that CG32744 retains conserved polyubiquitin-coding sequences across Drosophila species and is ubiquitously expressed, whereas CG11700 has accumulated numerous amino acid changes and shows a male-specific expression pattern. Null mutants of CG11700 have a higher male fecundity but shorter lifespan, whereas its overexpression decreases male fecundity. In contrast, the null mutants of the peptide-conserved CG32744 do not exhibit such phenotypes. These results suggest that CG11700 might have experienced neofunctionalization and evolved important functions in the trade-off between male fecundity and lifespan and that CG32744 likely has retained the ancestral function.     

Forced hot-air treatment against <Emphasis Type="Italic">Bactrocera papayae</Emphasis> (Diptera: Tephritidae) in papaya

The Asian papaya fruit fly, Bactrocera papayae Drew and Hancock, was treated with hot-water immersion and forced hot air to develop a phytosanitary heat treatment schedule. Hot-water immersion tests were conducted with 12- and 24-h-old eggs and with first and third instar larvae to compare the relative thermotolerances of this fruit fly among these life stages. The 24-h-old eggs, the most thermotolerant among the four life stages tested, were subjected to time and temperature tests using cage-infested papaya fruits in a forced hot-air chamber. Heating the papayas to a minimum core temperature of 47.7 °C (95% confidence interval 47.2–48.3 °C) was estimated to induce probit-nine mortality based on a probit analysis of the data. Confirmatory tests in which papayas infested with 24-h-old eggs were heated to a minimum fruit core temperature of 47.2 °C that was maintained for 0–30 min followed by hydrocooling to a fruit core temperature of ≈25 °C resulted in the complete mortality of an estimated treated population of 43,425 eggs aged 24 h (99.9931% mortality at the 95% confidence level). Therefore, heating the papaya fruits to a core temperature of 47.2 °C for a minimum dwell time of 30 min, which was the longest dwell time in the confirmatory tests, may serve as a phytosanitary heat treatment schedule for the control of B. papayae in papaya fruits.     

Dnmt1 overexpression causes genomic hypermethylation, loss of imprinting, and embryonic lethality

Biallelic expression of Igf2 is frequently seen in cancers because Igf2 functions as a survival factor. In many tumors the activation of Igf2 expression has been correlated with de novo methylation of the imprinted region. We have compared the intrinsic susceptibilities of the imprinted region of Igf2 and H19, other imprinted genes, bulk genomic DNA, and repetitive retroviral sequences to Dnmt1 overexpression. At low Dnmt1 methyltransferase levels repetitive retroviral elements were methylated and silenced. The nonmethylated imprinted region of Igf2 and H19 was resistant to methylation at low Dnmt1 levels but became fully methylated when Dnmt1 was overexpressed from a bacterial artificial chromosome transgene. Methylation caused the activation of the silent Igf2 allele in wild-type and Dnmt1 knockout cells, leading to biallelic Igf2 expression. In contrast, the imprinted genes Igf2r, Peg3, Snrpn, and Grf1 were completely resistant to de novo methylation, even when Dnmt1 was overexpressed. Therefore, the intrinsic difference between the imprinted region of Igf2 and H19 and of other imprinted genes to postzygotic de novo methylation may be the molecular basis for the frequently observed de novo methylation and upregulation of Igf2 in neoplastic cells and tumors. Injection of Dnmt1-overexpressing embryonic stem cells in diploid or tetraploid blastocysts resulted in lethality of the embryo, which resembled embryonic lethality caused by Dnmt1 deficiency.     

龙眼果实防腐保鲜技术研究

近几年来,我们探讨了不同的贮藏温度、化学防腐剂、气体组分、包装容器及包装方法对不同品种龙眼果实的防腐保鲜效果。结果表明:龙眼品种间的耐贮性有很大差异,按耐贮性排列:泉州本>乌龙岭>普明庵>福眼>赤壳>水涨;最佳的保鲜贮藏温度为3～4℃;仲丁胺、仲丁胺+赤霉素、多菌灵、甲基托布津、苯甲酸、特克多、FISB-1和FISB-2等不同化学防腐剂对泉州本的防腐效果,以FISB-1和FISB-2防腐效果最佳,贮藏40天,好果率分别为95.0％和95.2％,其他防腐剂处理的好果率为80.7％～86.5％;气调贮藏,CO_2为4％～6％,O_2为6％～8％的气体组分可延长贮藏寿命,降低龙眼果实自身损耗;包装容器以塑料周转箱套薄膜袋气调贮藏效果最佳。     

Design,synthesis and biological evaluation of 3-benzyloxy-linked pyrimidinylphenylamine derivatives as potent HIV-1 NNRTIs

A novel series of 3-benzyloxy-linked pyrimidinylphenylamine derivatives (8a–8s) was designed, synthesized and evaluated for their in vitro anti-HIV activity in MT-4 cell cultures. Most of the compounds inhibited wild-type (wt) HIV-1 replication in the lower micromolar concentration range (EC₅₀ = 0.05–35 μM) with high selectivity index (SI) values (ranged from 10 to >4870). In particular, 8h and 8g displayed excellent antiretroviral activity against wt HIV-1 with low cytotoxicity (EC₅₀ = 0.07 μM, CC₅₀ >347 μM, SI >4870; EC₅₀ = 0.05 μM, CC₅₀ = 42 μM, SI = 777, respectively), comparable to that of the marked drug nevirapine (EC₅₀ = 0.113 μM, CC₅₀ >15 μM, SI >133). In order to confirm the binding target, 8h was selected to perform the anti-HIV-1 RT assay. Additionally, preliminary structure activity relationship (SAR) analysis and molecular docking studies of newly synthesized compounds were also discussed, as well as the predicted physicochemical properties.     

Acacia Senegal–Inspired Bifunctional Binder for Longevity of Lithium–Sulfur Batteries

The sulfur cathode in traditional lithium–sulfur batteries suffers from poor cyclability due to polysulfide shuttling effect as well as large volume change during charge/discharge processes. Gum arabic (GA), a low cost, nontoxic, and sustainable natural polymer from Acacia senegal, is adopted as a binder for the sulfur cathode to address these issues. The excellent mechanical properties of GA endow the cathode with high binding strength and suitable ductility to buffer volume change, while the functional groups chemically and physically confine sulfur species within the cathode to inhibit the shuttling effect of polysulfides. Additionally, GA shifts the electrode fabrication process from the organic solvent process to an aqueous process, eliminates the use of toxic organic solvents, and achieves uniformly distributed electrode with lower impedance. A remarkable cycling performance, i.e., 841 mAh g^?1 at low current rate of C/5, is achieved throughout 500 cycles due to the bifunctions of the GA binder.