Lipid production by microalgae <Emphasis Type="Italic">Chlorella protothecoides</Emphasis> with volatile fatty acids (VFAs) as carbon sources in heterotrophic cultivation and its economic assessment

Volatile fatty acids (VFAs) that can be derived from food wastes were used for microbial lipid production by Chlorella protothecoides in heterotrophic cultures. The usage of VFAs as carbon sources for lipid accumulation was investigated in batch cultures. Culture medium, culture temperature, and nitrogen sources were explored for lipid production in the heterotrophic cultivation. The concentration and the ratio of VFAs exhibited significant influence on cell growth and lipid accumulation. The highest lipid yield coefficient and lipid content of C. protothecoides grown on VFAs were 0.187 g/g and 48.7 %, respectively. The lipid content and fatty acids produced using VFAs as carbon sources were similar to those seen on growth and production using glucose. The techno-economic analysis indicates that the biodiesel derived from the lipids produced by heterotrophic C. protothecoides with VFAs as carbon sources is very promising and competitive with other biofuels and fossil fuels.     

Niche characteristics of rodents by diverse disturbance in Alashan desert, Inner Mongolia, China

Four diverse disturbance types, namely, farmland, rotationally grazed grassland, overgrazed grassland and forbidden grazing grassland, were identified in the Alashan desert region of Inner Mongolia. Rodents were sampled in April, July and October in 2002 and 2003 using the trap-day method. Their spatial and temporal niches among the four disturbance types were assessed using the Shannon-Wiener niche breadth index and the Pianka niche overlap index. The Shannon-Wiener niche breadth index was the highest for Allactaga sibirica and Meriones meridianus (0.925 and 0.908, respectively), intermediate for Cricetulus eversmanni, Phodopus roborovskii and Citellus dauricus (0.789, 0.782 and 0.711, respectively), and lowest for Cardiocranius paradoxus (0.003). The Pianka niche overlap indices of six-paired species were the highest and varied from 0.900 to 1.000, suggesting their spatial niche overlapped almost completely. Conversely, the spatial niche overlap index for Meriones unguiculatus, Cardiocranius paradoxus, and Salpingotus kozlovi was zero, thus indicating a complete absence of competition among them. In addition, the temporal niche breadth and overlap indices varied greatly in relation to disturbance types and season. The level of temporal niche overlap in spring and autumn was low while in summer it was high. For all disturbance types and for each season, the temporal niche overlap index of Meriones meridianus and Cricetulus barabansis was always highest but for Meriones unguiculatus and Salpingotus kozlovi always lowest. __________ Translated from Acta Ecologica Sinica, 2005, 25(10): 2,637–2,643 [译自: 生态学报]     

Cleavage of territrems by alkaline hydrogen peroxide: Isolation and characterization of the aromatic moiety of territrems

The chemical reaction of cleavaging territrem B to give 3,4,5-trimethoxy benzoic acid by alkaline hydrogen peroxide was investigated. The method was applied for confirmation of the chemical structure of the aromatic moiety of territrem A, A’, B, and B’. The physicochemical properties of the aromatic cleavage product of territrem Aindicated the structure as 3,4-methylendioxy, 5-methoxy benzoic acid (or 4-methoxy, 6-carboxy, 1, 3-benzodioxole). The experiment also gave the evidences that territrem A and A’, on the other hand territrem B and B’ have the identical aromatic moieties on their structures.     

Landscape of target:guide homology effects on Cas9-mediated cleavage

To study target sequence specificity, selectivity, and reaction kinetics of Streptococcus pyogenes Cas9 activity, we challenged libraries of random variant targets with purified Cas9::guide RNA complexes in vitro. Cleavage kinetics were nonlinear, with a burst of initial activity followed by slower sustained cleavage. Consistent with other recent analyses of Cas9 sequence specificity, we observe considerable (albeit incomplete) impairment of cleavage for targets mutated in the PAM sequence or in ‘seed’ sequences matching the proximal 8 bp of the guide. A second target region requiring close homology was located at the other end of the guide::target duplex (positions 13–18 relative to the PAM). Sequences flanking the guide+PAM region had measurable (albeit modest) effects on cleavage. In addition, the first-base Guanine constraint commonly imposed by gRNA expression systems has little effect on overall cleavage efficiency. Taken together, these studies provide an in vitro understanding of the complexities of Cas9–gRNA interaction and cleavage beyond the general paradigm of site determination based on the ‘seed’ sequence and PAM.     

Genetic modification of alternative respiration in Nicotiana benthamiana affects basal and salicylic acid-induced resistance to potato virus X

Background  

Salicylic acid (SA) regulates multiple anti-viral mechanisms, including mechanism(s) that may be negatively regulated by the mitochondrial enzyme, alternative oxidase (AOX), the sole component of the alternative respiratory pathway. However, studies of this mechanism can be confounded by SA-mediated induction of RNA-dependent RNA polymerase 1, a component of the antiviral RNA silencing pathway. We made transgenic Nicotiana benthamiana plants in which alternative respiratory pathway capacity was either increased by constitutive expression of AOX, or decreased by expression of a dominant-negative mutant protein (AOX-E). N. benthamiana was used because it is a natural mutant that does not express a functional RNA-dependent RNA polymerase 1.     

Dilated cardiomyopathy caused by tissue-specific ablation of SC35 in the heart

Many genetic diseases are caused by mutations in cis-acting splicing signals, but few are triggered by defective trans-acting splicing factors. Here we report that tissue-specific ablation of the splicing factor SC35 in the heart causes dilated cardiomyopathy (DCM). Although SC35 was deleted early in cardiogenesis by using the MLC-2v-Cre transgenic mouse, heart development appeared largely unaffected, with the DCM phenotype developing 3-5 weeks after birth and the mutant animals having a normal life span. This nonlethal phenotype allowed the identification of downregulated genes by microarray, one of which was the cardiac-specific ryanodine receptor 2. We showed that downregulation of this critical Ca2+ release channel preceded disease symptoms and that the mutant cardiomyocytes exhibited frequency-dependent excitation-contraction coupling defects. The implication of SC35 in heart disease agrees with a recently documented link of SC35 expression to heart failure and interference of splicing regulation during infection by myocarditis-causing viruses. These studies raise a new paradigm for the etiology of certain human heart diseases of genetic or environmental origin that may be triggered by dysfunction in RNA processing.     

Comparative study of the cytotoxicity of the nanosized and microsized tellurium powders on HeLa cells

To compare the cytotoxicity on HeLa cells induced by nanosized and microsized tellurium powders, HeLa cells were exposed to different concentrations of tellurium powders (0, 50, 100, 150 and 200 μg/mL) for 12 h. In this study, detection of a series of biomarkers, including reactive oxygen species (ROS), glutathione (GSH), 8-hydroxy-2′-deoxyguanosine (8-OHdG), in addition to DNA and protein crosslink (DPC) and MTTassay, were conducted to evaluate the cytotoxicity. It is indicated that compared with the control group, there was no significant difference in the induced cytotoxicity at concentrations lower than 50 μg/mL for both nanosized and microsized tellurium powders. While there appears a significant difference in the induced cytotoxicity for nanosized tellurium powders when the concentration is higher than 100 μg/mL as well as for microsized tellurium powders when the concentration is higher than 200 μg/mL. Moreover, it is found that the cytotoxicity induced on HeLa cells exhibits a certain dose-effect relationship with the concentration of tellurium powders. A conclusion has been reached that the toxicity on HeLa cells can be induced by both nanosized and microsized tellurium powders, and the toxicity of the nanosized tellurium powders is significantly greater than the microsized one.     

CHIP facilitates ubiquitination of inducible nitric oxide synthase and promotes its proteasomal degradation

Inducible nitric oxide synthase (iNOS) is responsible for nitric oxide (NO) synthesis from l-arginine in response to inflammatory mediators. It is reported that iNOS is degraded mainly by the ubiquitin-proteasome pathway in RAW264.7 cells and human embryonic kidney (HEK) 293 cells. In this study, we showed that iNOS was ubiquitinated and degraded dependent on CHIP (COOH terminus of heat shock protein 70-interacting protein), a chaperone-dependent ubiquitin ligase. The results from overexpression and RNAi experiments demonstrated that CHIP decreased the protein level of iNOS, shortened the half-life of iNOS and attenuated the production of NO. Furthermore, CHIP promoted ubiquitination and proteasomal degradation of iNOS by associating with iNOS. These results suggest that CHIP plays an important role in regulation iNOS activity.