Characterization of metabolically active developmental stage of Aspergillus niger cells immobilized in polyacrylamide gel

Summary The in-situ development of Aspergillus niger entrapped in polyacrylamide gel from spores and the gel surface characteristics were studied during the repeated shake flask batch citric acid fermentation. A marked increase in the rate of citric acid production was observed with the periodic replacement of culture with fresh media at an interval of 6 days reducing the fermentation time nearly to half. The metabolically active A. niger cells for citric acid production were characterized by the appearance of thick and bulbous hyphae scattered in and on the gel surface.     

Interaction of heavy metal toxicants with brain constitutive nitric oxide synthase

This study was designed to evaluate thein vitro effects of transition heavy metal cations on activity of constitutive isoform of nitric oxide synthase (cNOS) in rat brain. NOS activity was determined in the cytosolic fractions of rat cerebral hemispheres by conversion of³H-L-arginine to³H-L-citrulline. Different concentrations of mercury (Hg²⁺), nickel (Ni²⁺), manganese (Mn²⁺), zinc (Zn²⁺), cadmium (Cd²⁺), lead (Pb²⁺) and calcium (Ca²⁺) were tested on NOS activity. While all the cations caused inhibition, there were differences in the apparent inhibition constants (Ki) among the cations. With the exception of calcium ion no other cation required preincubation with the enzyme preparation. These results indicate that while calcium ion modulate cNOS activity at regulatory site(s), inhibitory influence of toxic heavy metal cations may be exerted on the catalytic site(s) either by direct binding to it or by interfering with the electron transfer during catalysis.     

A photomap of the salivary gland chromosomes of Anopheles stephensi liston (Culicidae: Diptera)

A photomap of the banding pattern of the salivary gland chromosomes of Anopheles stephensi Liston, which is first of its kind, has been prepared. The salivary chromosome complement consists of five arms, the shortest of which represents the telocentric X-chromosome, and the remaining four the autosomal arms. A comparison has been made of the banding pattern of this species with other species of the subgenus Cellia.     

Fatty acid activation of guanylate cyclase from fibroblasts and liver.

Sodium arachidonate and sodium oleate increased particulate guanylate cyclase activity from homogenates of Balb 3T3 cells or rat liver. The fatty acids were about equipotent and were maximally effective at about 100 μm concentrations. Higher concentrations were less effective or inhibitory. Activation was similar in an air or nitrogen atmosphere and was unaltered by KCN, aspirin, or indomethacin. The dose-response curve was shifted to the right when arachidonate was preincubated prior to its addition to guanylate cyclase assays. Agents that facilitate fatty acid oxidation and the formation of malonyldialdehyde during preincubation such as glutathione, hemoglobin, Mn²⁺, Fe³⁺, or lipoxygenase shifted the dose-response curve further to the right. In contrast, agents that decreased or prevented arachidonate oxidation and malonyldialdehyde formation during preincubation such as butylated hydroxyanisole, propyl gallate, hydroquinone, and diphenylfuran prevented the shift in the dose-response curve or in some instances shifted the dose-response curve to the left. Activation of guanylate cyclase by arachidonate was reversed by the addition of lipoxygenase to incubations. These studies indicate that unsaturated fatty acids and not their oxidation products activate particulate enzyme from Balb 3T3 cells. The mechanism of fatty acid activation appears to be different from activation by nitro compounds. Fatty acids but not nitro compounds activated fibroblast preparations, and the effect of fatty acids in contrast to the activation by nitroprusside in liver preparations was not prevented with Lubrol PX.     

Evaluation of chemical methods for estimating available zinc and response of green gram (Phaseolus aureus roxb) to applied zinc in non-calcareous soils

Summary Studies were conducted in 22 non-calcareous soils (India) to evaluate various extractants,viz. (6N HCl, 0.1N HCl, EDTA (NH₄)₂CO₃, EDTA NH₄OAc, DTPA+CaCl₂ and 1M MgCl₂) to find critical levels of soil and plant Zn for green gram (Phaseolus aureus Roxb.). The order of extractability by the different extractants was 6N HCl>0.1N HCl>EDTA (NH₄)₂CO₃<EDTA NH₄OAc DTPA+CaCl₂>1M MgCl₂. Critical levels of 0.48 ppm DTPA × CaCl₂ extractable Zn, 0.80 ppm EDTA NH₄OAc extractable Zn, 0.70 ppm EDTA (NH₄)₂CO₃ extractable Zn, and 2.2 ppm 0.1N HCl extractable Zn were estimated for the soils tested. The critical Zn concentration in 6 weeks old plants was found to be 19 ppm. The 0.1N HCl method gave the best correlation (r=0.588^**) between extractable Zn and Bray's per cent yield, while with DTPA+CaCl₂, it was slightly low (r=0.542^**). The DTPA + CaCl₂ method gave significant (r=0.73^**) correlation with plant Zn concentration. The 0.1N HCl gave the higher correlation with Zn uptake (r=0.661^**) than DTPA (r=0.634^**) 6N HCl and 1M MgCl₂ method gave nonsignificant positive relationship with Bray's per cent yield. For noncalcareous soils apart from the common use of DTPA+CaCl₂, 0.1N HCl can also be used for predicting soil available Zn. The use of 0.1N HCl would be much cheaper than DTPA and other extractants used in the study.     

Chemical equilibrium and E value of Zn (ZnE) in inceptisols and entisols of tropical india

Summary The chemical equilibrium and E value for Zn was calculated in 9 soils of Haryana (India) which represented mainly entisol and inceptisols. The rate of isotopic exchange between⁶⁵Zn and native soil Zn was quite rapid and radioactivity reduced to about 0.2 per cent of initial activity after 3 days but total Zn concentration in soil solution did not decrease. In 5 out of 9 soils equilibrium was established in 2 to 3 days. In typic ustochrepts having high clay content (3,4) equilibrium was attained in two days. In typic udipsamments (2), typic camborthids (8) and aquic vertic ustichrepts (9) it took 3 days to set equilibrium. Typic ustochrepts (5) took 5 days for equilibrium whereas typic ustipssaments (6) and typic camborthids of high O.C. did not attain equilibrium even in 7 days. This indicated that the chemistry and availability of Zn in soil would depend on soil types. When Zn_E was estimated by applying activity after equilibrium with carrier Zn and by applying activity with carrier Zn before equilibrium was set, there was no agreement in Zn_E in two methods. Increasing Zn_E with increasing Zn dose was observed by both methods only in alkaline typic ustochrept (4). In some soils higher E values than added amounts were observed, whereas, in soil 8 negative E values were obtained. The E values become erratic and are over estimated where complex reactions take place due to high pH, high O.C. and high complex forming elements.     

Effects of thiols, sugars, and proteins on nitric oxide activation of guanylate cyclase.

Purification of soluble guanylate cyclase from rat liver resulted in an apparent loss of enzyme activation by nitric oxide that could be restored by dithiothreitol. methemoglobin, bovine serum albumin, or sucrose. Although hemoglobin also permitted some activation with nitric oxide, the effect of other agents to restore enzyme activation was prevented with hemoglobin. As a result of enzyme purification, there is an alteration of the dose-response relationship for nitric oxide activation. After partial enzyme purification, relatively high concentrations of nitric oxide that were stimulatory in crude enzyme preparations had no effect on enzyme activity. However, partially purified or homogeneous enzyme was activated by lower concentrations of nitric oxide. The bell-shaped dose-response curve for nitric oxide was shifted to the left with guanylate cyclase purification. The addition of dithiothreitol, methemoglobin, bovine serum albumin, or sucrose to enzyme markedly broadens the dose-response curve for nitric oxide. Thus, the apparent loss of responsiveness to nitric oxide with purification is a function of increased sensitivity of guanylate cyclase to nitric oxide. Increased sensitivity to nitric oxide with enzyme purification probably results from the removal of heme, proteins, and small molecules that can serve as scavengers or sinks for nitric oxide and prevent excessive oxidation of the enzyme.     

Association genetics of the parameters related to nitrogen use efficiency in Brassica juncea L.

Key message

Genome wide association studies allowed prediction of 17 candidate genes for association with nitrogen use efficiency. Novel information obtained may provide better understanding of genomic controls underlying germplasm variations for this trait in Indian mustard.

Abstract

Nitrogen use efficiency (NUE) of Indian mustard (Brassica juncea (L.) Czern & Coss.) is low and most breeding efforts to combine NUE with crop performance have not succeeded. Underlying genetics also remain unexplored. We tested 92 SNP-genotyped inbred lines for yield component traits, N uptake efficiency (NUPEFF), nitrogen utilization efficiency (NUTEFF), nitrogen harvest index (NHI) and NUE for two years at two nitrogen doses (N_o without added N and N₁₀₀ added @100 kg/ha). Genotypes IC-2489-88, M-633, MCP-632, HUJM 1080, GR-325 and DJ-65 recorded high NUE at low N. These also showed improved crop performance under high N. One determinate mustard genotype DJ-113 DT-3 revealed maximum NUTEFF. Genome wide association studies (GWAS) facilitated recognition of 17 quantitative trait loci (QTLs). Environment specificity was high. B-genome chromosomes (B02, B03, B05, B07 and B08) harbored many useful loci. We also used regional association mapping (RAM) to supplement results from GWAS. Annotation of the genomic regions around peak SNPs helped to predict several gene candidates for root architecture, N uptake, assimilation and remobilization. CAT9 (At1g05940) was consistently envisaged for both NUE and NUPEFF. Major N transporter genes, NRT1.8 and NRT3.1 were predicted for explaining variation for NUTEFF and NUPEFF, respectively. Most significant amino acid transporter gene, AAP1 appeared associated with NUE under limited N conditions. All these candidates were predicted in the regions of high linkage disequilibrium. Sequence information of the predicted candidate genes will permit development of molecular markers to aid breeding for high NUE.