The feasibility of using the FLP/ FRT site-specific recombination system in rice for genome engineering was evaluated. Transgenic rice plants expressing the FLP recombinase were crossed with plants harbouring the kanamycin resistance gene ( neomycin phosphotransferase II , nptII ) flanked by FRT sites, which also served to separate the corn ubiquitin promoter from a promoterless gusA . Hybrid progeny were tested for excision of the nptII gene and the positioning of the ubiquitin promoter proximal to gusA . While the hybrid progeny from various crosses exhibited β-glucuronidase (GUS) expression, the progeny of selfed parental rice plants did not show detectable GUS activity. Despite the variable GUS expression and incomplete recombination displayed in hybrids from some crosses, uniform GUS staining and complete recombination were observed in hybrids from other crosses. The recombined locus was shown to be stably inherited by the progeny. These data demonstrate the operation of FLP recombinase in catalysing excisional DNA recombination in rice, and confirm that the FLP/ FRT recombination system functions effectively in the cereal crop rice. Transgenic rice lines expressing active FLP recombinase generated in this study provide foundational stock material, thus facilitating the future application and development of the FLP/ FRT system in rice genetic improvement. 相似文献
The amino acid at position 55 of the E2 glycoprotein (E2(55)) of Sindbis virus (SV) is a critical determinant of SV neurovirulence in mice. Recombinant virus strain TE (E2(55) = histidine) differs only at this position from virus strain 633 (E2(55)= glutamine), yet TE is considerably more neurovirulent than 633. TE replicates better than 633 in a neuroblastoma cell line (N18), but similarly in BHK cells. Immunofluorescence staining showed that most N18 cells were infected by TE at a multiplicity of infection (MOI) of 50 to 500 and by 633 only at an MOI of 5,000, while both viruses infected essentially 100% of BHK cells at an MOI of 5. When exposed to pH 5, TE and 633 viruses fused to similar extents with liposomes derived from BHK or N18 cell lipids, but fusion with N18-derived liposomes was less extensive (15 to 20%) than fusion with BHK-derived liposomes ( approximately 50%). Binding of TE and 633 to N18, but not BHK, cells was dependent on the medium used for virus binding. Differences between TE and 633 binding to N18 cells were evident in Dulbecco's modified Eagle medium (DMEM), but not in RPMI. In DMEM, the binding efficiency of 633 decreased significantly as the pH was raised from 6.5 to 8.0, while that of TE did not change. The same pattern was observed with RPMI when the ionic strength of RPMI was increased to that of DMEM. TE bound better to heparin-Sepharose than 633, but this difference was not pH dependent. Growth of N18 and BHK cells in sodium chlorate to eliminate all sulfation decreased virus-cell binding, suggesting the involvement of sulfated molecules on the cell surface. Taken together, the presence of glutamine at E2(55) impairs SV binding to neural cells under conditions characteristic of interstitial fluid. We conclude that mutation to histidine participates in or stabilizes the interaction between the virus and the surface of neural cells, contributing to greater neurovirulence. 相似文献
Cis-diamminedichloroplatinum(II) (cisplatin) (CP) is an important chemotherapeutic agent used in the treatment of several cancers. However, it has several side effects including nephrotoxicity gonadotoxicity, hepatotoxicity, and ototoxicity. In in vitro experiments, antioxidants or reactive oxygen species scavengers have a cytoprotective effect on cells exposed to cisplatin (CP). Ellagic acid (EA) is one such bioactive polyphenol that is abundant in some fruits, nuts, and seeds. Various authors have reported that EA has strong antioxidant and antitumor potential. The present study was, therefore, carried out to explore the protective potential of EA on CP-induced gonadotoxicity and nephrotoxicity in colon tumor-bearing mice. Animals were divided into five groups: Group I: normal control, Group II: DMH treated. After 20 weeks of DMH treatment, the animals were divided into four subgroups, viz., Group III: no treatment, Group IV: EA, Group V: CP, and Group VI: CP?+?EA. Administration of EA significantly ameliorated the toxicity caused by CP as indicated by improved kidney function tests and reproductive function tests. EA treatment to CP-abused mice also led to a marked reduction in the extent of peroxidative damage to tissue as was evident from the improvement in the histopathological changes in kidney and testis. Blood counts were also improved on administration of EA to CP-treated mice. This article provides the evidence that antioxidant efficacy of EA has beneficial effects on CP-induced nephrotoxicity and gonadotoxicity and contributes to understanding the role of oxidative stress, and suggests several points as part of the mechanism of CP toxicity.
Sequencing batch reactors were used to study anaerobic ammonium oxidation (anammox) process under temperature shock. Both long-term (15–35 °C) and short-term (10–50 °C) temperature effects on nitrogen removal performance were performed. In reactor operation test, the results indicated that ammonium removal rate decreased from 0.35 kg/(m3 day) gradually to 0.059 kg/(m3 day) when temperature dropped from 35 to 15 °C. Although bacteria morphology was not modified, sludge settling velocity decreased with decreasing temperature. In batch test, apparent activation energy (Ea) increased with decreasing temperature, which suggested the activity decrease of anaerobic ammonium oxidizing bacteria (AAOB). Low temperature inhibited AAOB and weakened nitrogen removal performance. The cardinal temperature model with inflection was first used to describe temperature effect on anammox process. Simulated results revealed that anammox reaction could occur at 10.52–50.15 °C with maximum specific anammox activity of 0.50 kg/(kg day) at 36.72 °C. The cold acclimatization of AAOB could be achieved and glycine betaine could slightly improve nitrogen removal performance at low temperature. 相似文献
Transgenic cotton has shown great promise for the control of target pest insects; however, frequent outbreaks of nontarget pest mirids has been recorded in recent years in northern China. To test the hypothesis that transgenic cotton contributes to nontarget pest outbreaks, we studied the impact of transgenic Bt cottons (both Bt and Bt + CpTI) on the fitness of nontarget pest Adelphocoris suturalis Jakovlev. No significant differences were detected between population densities of A. suturalis in unsprayed nontransgenic cottons and in unsprayed transgenic Bt cottons in 2007, 2008, and 2009. No difference in preferred oviposition site or egg production was detected between transgenic and nontransgenic cottons in both free choice and no choice tests. No difference in life table parameters was detected for A. suturalis between Bt cottons and nontransgenic cottons. All these results indicated that transgenic crops did not contribute to the nontarget pest outbreaks when being compared with their parental lines. The possible reasons for intensified pest status of A. suturalis, such as decrease of pesticide application, deficient natural enemies, and area-wide shift of cotton varieties, were discussed. 相似文献