Effect of mutations on acetohydroxyacid synthase(AHAS)function in Cyperus difformis L.

Cyperus difformis L.is a troublesome weed in paddy fields and has attracted attention due to its resistance to acetohydroxyacid synthase(AHAS)inhibitors.It was found that the amino acid mutation in AHAS was the primary cause for the resistance of Cyperus difformis.However,the effect of different mutations on AHAS function is not clear in Cyperus difformis.To confirm the effect of mutations on AHAS function,six biotypes were collected,including Pro197Arg,Pro197Ser,Pro197Leu,Asp376Glu,Trp574Leu and wild type,from Hunan,Anhui,Jiangxi and Jiangsu provinces,China and the function of AHAS was characterized.The AHAS in vitro inhibition assay results indicated that the mutations decreased the sensitivity of AHAS to pyrazosulfuron-ethyl,in which the I_(50)(the half maximal inhibitory concentration)of wild type AHAS was 0.04μmol L^(-1)and Asp376Glu,Pro197Leu,Pro197Arg,Pro197Ser and Trp574Leu mutations were 3.98,11.50,40.38,38.19 and 311.43μmol L^(-1),respectively.In the determination of enzyme kinetics parameters,the Km and the maximum reaction velocity(Vmax)of the wild type were 5.18 mmol L^(-1)and 0.12 nmol mg^(-1)min^(-1),respectively,and the Km values of AHAS with Asp376Glu,Trp574Leu,Pro197Leu and Pro197Ser mutations were 0.38-0.93 times of the wild type.The Km value of the Pro197Arg mutation was 1.14times of the wild type,and the Vmax values of the five mutations were 1.17-3.33-fold compared to the wild type.It was found that the mutations increased the affinity of AHAS to the substrate,except for the Pro197Arg mutation.At a concentration of 0.0032-100 mmol L^(-1)branched-chain amino acids(BCAAs),the sensitivity of the other four mutant AHAS biotypes to feedback inhibition decreased,except for the Pro197Arg mutation.This study elucidated the effect of different mutations on AHAS function in Cyperus difformis and provided ideas for further study of resistance development.

Phytochemistry, anti-asthmatic and antioxidant activities of Anchomanes difformis(Blume) Engl. leaf extract

Objective: To study the phytochemistry, anti-asthmatic and antioxidant activities of the aqueous leaf extract of Anchomanes difformis(Blume) Engl.(A. difformis) and to verify claims of use in folk medicine.Methods: For anti-asthmatic activity, male and female guinea pigs with average body weight of(451.4 ± 118.1) g were divided into six groups of six animals each. Group 1served as control(distilled water); Group 2 was administered with salbutamol(reference drug) only; Group 3 served as ovalbumin sensitized group, Group 4, 5 and 6 were treated with A. difformis extract at doses of 100, 200 and 400 mg/kg, respectively. Described methods were used to test fluid viscosity, fluid volume and quantitative phytochemistry analysis. Absorbance was read using a UV–Vis spectrophotometer and results computed in percentage. Total antioxidant assays [2, 2-diphenyl-1-picrylhydrazyl(DPPH) and lipid peroxidation assay], were carried out using reported procedures.Results: The anti-asthmatic evaluation showed that protection from asthma of the animals in Group 6(400 mg/kg, 32.7%) were similar to that in Group 2(salbutamol, 33.0%).Excised trachea was free of mucus secretion in Group 5(200 mg/kg) as was observed in the control group. Fluid volume increase in Groups 3 and 6 indicated mucus secretion.DPPH radical scavenging activity of extract was effective as ascorbic acid which served as standard at 20 mg/m L. But, the extract elicited low lipid peroxidation activity compared with the reference(tocopherol) at concentrations tested.Conclusions: A. difformis aqueous leaf extract is safe and possesses positive antiasthmatic and antioxidant activities as claimed by traditional herbal practitioners in Delta State.

Laboratory evaluation of the toxic properties of forest anchomanes, Anchomanes difformis against pulse beetle Callosobruchus maculatus （Coleoptera： Bruchidae）

Laboratory experiments were carried out to investigate the efficacy of crude stem extracts of forest anchomanes, Anchomanes difformis （P. Beauv.） a plant occurring in West African forests, against the pulse beetle Callosobruchus maculattts （Fabricius）. Crude stem extracts at 3% concentration showed high contact toxicity to adult beetles within 24 h after application, while it was moderately toxic to the beetles at the lowest （1%） concentration. At the highest application rate, the plant extract provided good protection to grains stored for 90 days. Grain viability and water absorption capacity were not affected by treatments with ethanol extracts ofA. difformis. The significance of these findings is discussed in relation to biopesticide-means of controlling cowpea bruchids.

Isolation, characterization and modulatory potentials of β-stigmasterol, ergosterol and xylopic acid from Anchomanes difformis on mitochondrial permeability transition pore in vitro

Objective: Secondary metabolites and polyphenolic compounds from medicinal plants have been demonstrated to have multiple biological functions with promising research and development prospects. This study examined the effect of β-stigmasterol(with ergosterol) and xylopic acid isolated from Anchomanes difformis on liver mitochondrial permeability transition pore(mPTP).Methods: The compounds were isolated by vacuum liquid chromatography. Mitochondrial swelling was assessed as changes in absorbance under succinate-energized conditions.Results:1H and13C NMR spectroscopic elucidation of the isolates affirmed the presence of β-stigmasterol with ergosterol(1:0.3) and xylopic acid. The isolates reversed the increase in lipid peroxidation and inhibited the opening of mitochondrial permeability transition pores caused by calcium and glucose.Pharmacological inhibition of m PTP offers a promising therapeutic target for the treatment of mitochondrial-associated disorders.Conclusion: Reduction in the activity of calcium ATPase and the expression of Caspase-3 and-9 were observed, suggesting that they could play a role in protecting physicochemical properties of membrane bilayers from free radical-induced severe cellular damage and be useful in the management of diseases where much apoptosis occurs.

异型莎草对不同除草剂的敏感性研究

采用盆栽法茎叶处理方式分别测定了湖南省4个地区的水田异型莎草(Cyperus difformis L.)对灭草松、二甲四氯、吡嘧磺隆、氯吡嘧磺隆、五氟磺草胺5种除草剂的敏感性。结果表明,各异型莎草种群对灭草松和二甲四氯均敏感,鲜重抑制率达90%以上;种群H1、H4对氯吡嘧磺隆不敏感,鲜重抑制率最高达32.12%;种群H1、H3、H4对吡嘧磺隆产生抗性,其ED50分别为6 397.17、194.18、198.06 g(a.i.)/hm2,且这3个种群对五氟磺草胺产生交互抗性,但种群H2对吡嘧磺隆和五氟磺草胺均敏感。

Biological Characteristies of Methane Emission of Oryzasativa，Panicumcrus－galliand Cyperusdif for misGrown on PaddySoil

Biological characteristics of methane emission were compared among Oryza sativa, Panicum crus-galli andCyperus difformis grown on paddy soil. The order of the amounts of methane emitted was P. crus-galli > O. sativa >C. difformis, with the former two 11 and 8 times as much as that of the latter, respectively. And it was just opposite tothat of the methane-forming activities of roots of the three plants. The diurnal changes of methane emission of thethree plants were relatively consistent with valleys during 11:00-14:00 and midnight and peaks during 8:00-11: 00,14:00- 20:00 and about 5:00 early morning. The methanogenic activites in rhizospheric soils were higher than those innonrhizospheric soils with P. crus-galli and O. sativa, but not with C. difformis. The pathways of methane release ofP. crus-galli and O . sativa were probably through the top gaps near the junctions of nodal plate and leaf sheath, how-ever in C. difformistopgaps from which methane could escape into atmosphere were not found.