Silicon and Nitric Oxide-Mediated Regulation of Growth Attributes,Metabolites and Antioxidant Defense System of Radish (<i>Raphanus sativus</i> L.) under Arsenic Stress

Arsenic (As) contaminated food chains have emerged as a serious public concern for humans and animals and are known to affect the cultivation of edible crops throughout the world. Therefore, the present study was designed to investigate the individual as well as the combined effects of exogenous silicon (Si) and sodium nitroprusside (SNP), a nitric oxide (NO) donor, on plant growth, metabolites, and antioxidant defense systems of radish (Raphanus sativus L.) plants under three different concentrations of As stress, i.e., 0.3, 0.5, and 0.7 mM in a pot experiment. The results showed that As stress reduced the growth parameters of radish plants by increasing the level of oxidative stress markers, i.e., malondialdehyde and hydrogen peroxide. However, foliar application of Si (2 mM) and pretreatment with SNP (100 µM) alone as well as in combination with Si improved the plant growth parameters, i.e., root length, fresh and dry weight of plants under As stress. Furthermore, As stress also reduced protein, and metabolites contents (flavonoids, phenolic and anthocyanin). Activities of antioxidative enzymes such as catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (POD), and polyphenol oxidase (PPO), as well as the content of non-enzymatic antioxidants (glutathione and ascorbic acid) decreased under As stress. In most of the parameters in radish, As III concentration showed maximum reduction, as compared to As I and II concentrations. However, the individual and combined application of Si and NO significantly alleviated the As-mediated oxidative stress in radish plants by increasing the protein, and metabolites content. Enhancement in the activities of CAT, APX, POD and PPO enzymes were recorded. Contents of glutathione and ascorbic acid were also enhanced in response to co-application of Si and NO under As stress. Results obtained were more pronounced when Si and NO were applied in combination under As stress, as compared to their individual application. In short, the current study highlights that Si and NO synergistically regulate plant growth through lowering the As-mediated oxidative stress by upregulating the metabolites content, activity of antioxidative enzymes and non-enzymatic antioxidants in radish plants.

     

Human DNA helicase IV is nucleolin, an RNA helicase modulated by phosphorylation

The cDNA encoding human DNA helicase IV (HDH IV), a 100-kDa protein which unwinds DNA in the 5′ to 3′ direction with respect to the bound strand, was cloned and sequenced. It was found to be identical to the human cDNA encoding nucleolin, a ubiquitous eukaryotic protein essential for pre-ribosome assembly. HDH IV/nucleolin can unwind RNA-RNA duplexes, as well as DNA-DNA and DNA-RNA duplexes. Phosphorylation of HDH IV/nucleolin by cdc2 kinase and casein kinase II enhanced its unwinding activity in an additive way. The Gly-rich C-terminal domain possesses a limited ATP-dependent duplex-unwinding activity which contributes to the helicase activity of HDH IV/nucleolin.     

Effects of fusicoccin on Fresh Weight and Chlorophyll Levels in Cucumber Cotyledons

Incubation of cucumber cotyledons with fusicoccin increasedtheir fresh weights and chlorophyll levels and this effect wasenhanced by KCl. Addition of fusicoccin to this combinationincreased fresh weights but decreased chlorophyll levels. Thissuggests that the effects of fusiccocin on these two processesare probably mediated via different mechanisms. (Received January 4, 1982; Accepted March 25, 1982)     

Ionophore-mediated Ca2+ countertransport: role of Na+, Li+ or H+ gradient

Summary In an artificial system, the ionophore A23187, which transports Ca²⁺ but not Na⁺, is able to mediate the uphill translocation of Ca²⁺ from one aqueous medium to another across an organic immiscible phase, provided that a Na⁺, Li⁺ or H⁺ gradient is imposed on the system. Therefore, in the process known as Na-Ca countertransport, the downhill influx of Na⁺ may not be necessary for causing Ca²⁺ extrusion against its electrochemical gradient.     

Increase in Lysolecithin Content of Brain Microsomes in Phenobarbitone-Administered Rats and Its Relation to Lipid Peroxidation

Administration of phenobarbitone caused a marked increase in the capacity of rat brain microsomes to produce thiobarbituric acid-reactive substances in vitro. Enzymatic peroxidation of lipids was more affected than the nonenzymatic processes occurring in heat-inactivated preparations. Analysis of the phospholipid profile showed a drastic decrease in phosphatidylcholine and total phospholipid contents in the exposed animals, but about a fivefold increase in the lysophosphatidylcholine fraction. Data for in vivo incorporation of [14C]choline showed a similar pattern of high radioactivity in lysolecithin. The increase in lipid peroxidation could be related to the higher level of lysolecithin and the accompanying structural and functional changes in microsomes resulting from the neurotoxic effects of phenobarbitone.     

Isolation and characterisation of cathepsin-B from bovine pancreas

A simple procedure for the isolation of cathepsin-B from bovine pancreas employing ammonium sulphate fractionation, DEAE cellulose chromatography and Sephadex G-200 gel filtration is described. The purified enzyme gave a single band on polyacrylamide gel electrophoresis. The molecular weight as determined by gel filtration of the enzyme was 26,850. ItsK _m andV _max values were 12.8 mM and 0.303 Μmol/min/mg, respectively. TheK _i for iodoacetamide was 0.16 mM.     

Comparative analysis of metabolites in contrasting chickpea cultivars

Journal of Plant Biochemistry and Biotechnology - Chickpea (Cicer arietinum L.) is a good source of nutrients for animals and human consumption. In the present study, we analyzed the anthocyanin...