Showing papers by "Kavita Shah published in 2013"

Effect of cadmium uptake and heat stress on root ultrastructure, membrane damage and antioxidative response in rice seedlings

Abstract: Excess cadmium (Cd2+) in the soil environment is taken up by plants and can cause phytotoxicity. Elevated temperatures also lead to deleterious effects on plants. Plants are very often exposed to a combination of stresses rather than a single stress. The effect of Cd2+ and heat stress (HS) on the growth, root ultrastructure, lipid peroxidation (MDA), hydrogen peroxide accumulation and the activities of antioxidant enzymes peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) of rice roots from sensitive cv. DR-92 and tolerant cv. Bh-1 were investigated at 10 and 20 day of growth under controlled conditions. At day 10 under all Cd2+ treatments, the Cd2+ content between the two rice cultivars were almost similar. Application of 500 μM Cd2+ significantly increased metal concentrations at day 20 in the roots of rice seedlings resulting in a maximum accumulation of 44.25 μg Cd2+ g-1 dry wt in cv. DR-92 and 30 μg Cd2+ g-1 dry wt in cv. Bh-1 with a ~25 % decline in Relative Growth Index (RGI) in cv. DR-92. TEM studies revealed slight disorganization with cell wall ingrowths in root tissues from cv. DR-92 grown in 100 μM Cd2+ + HS. Uptake and accumulation of Cd2+ increased upon heat treatment in parenchyma, vacuoles and vascular cylinder of root tissues. Peroxidase primarily located in cell walls, the intensity being higher in sensitive cv. DR-92. Under Cd2+ stress alone, plants of sensitive cv. DR-92 significantly increased the H2O2 and MDA levels together with increased activities of the enzymes POD, CAT and APX at day 10 but remained almost stable at day 20. A strong increase in MDA levels was noted at day 20 in tolerant cv. Bh-1. Cd2+ + HS treatments in tolerant cv.Bh-1 led to a decreased H2O2 and MDA levels and decreased activities of the enzymes POD, CAT and APX. Results suggest stimulation of root antioxidant system under combination of two stresses and that heat stress seem to have a direct protective role by mitigating the effect of mild Cd2+ toxicity largely by enhanced Cd2+-MT formation contributing thereby towards the management of Cd2+ toxicity at cellular level that confers Cd2+ tolerance to rice cv. Bh-1.

Structural Simulation of MHC-peptide Interactions using T-cell Epitope in Iron-acquisition Protein of N. meningitides for Vaccine Design

Abstract: The present work uses a structural simulation approach to identify the potential target vaccine candidates or T cell epitopes (antigenic region that can activate T cell response) in two iron acquisition proteins from Neisseria. An iron regulated outer membrane protein frpB: extracellular, (NMB1988), and a Major ferric Iron-binding protein fbpA: periplasmic, (NMB0634) critical for the survival of the pathogen in the host were used. Ten novel promiscuous epitopes from the two iron acquisition proteins were identified using bioinformatics interface. Of these epitopes, 630 VQKAVGSIL 638 present on frpB with high binding affinity for allele HLA*DR1 was identified with an anchor position at P2, an aliphatic residue at P4 and glycine at P6making it thereby a potentialquality choice for linking peptide-loaded MHC dynamics to T-cell activation and vaccine constructs. The feasibility and structural binding of predicted peptide to the respective HLA allele was investigated by molecular modeling and template-based structural simulation. The conformational properties of the linear peptide were investigated by molecular dynamics using GROMOS96 package and Swiss PDB viewer.

PHYLOGENETIC RELATIONSHIPS IN ZnT SUPERFAMILY OF ZINC ION TRANSPORTERS IN SILICO

Abstract: The Zinc transporter (ZnT superfamily) facilitates Zn-transport into intracellular vesicles in life forms. Existing database has been enriched with the identification of new Zn-transporters important for therapeutic and intra-channel metal binding capacity. The present work uses a consensus sequence approach to identify extra-membrane metal-binding motif in Zn transporter protein family. Molecular phylogeny among members of ZnT superfamily proteins was analyzed. In all 166 representative sequences covering all known members of ZnT protein subfamilies (subgroups Znt1-Znt10) from bacteria, archaea and eukarya were selected and used to obtain ten consensus sequences, each representing a specific ZnT subgroup (1-10). Using bioinformatics tools a phylogenetic tree was constructed to explore the evolutionary link between the various ZnT subgroup considering members from lower and higher life forms. The unrooted phylogenetic tree obtained by Clustal W and NJ method revealed the existence of three clearly separated clades, which were segregated early in the evolution of this superfamily. Consensus sequence analysis using Weblogo revealed motifs of (HX)n type that evolved to bind the Zn ions effectively, enabling Zn transport. No significant similarity among members of Znt1 and Znt10 or Znt2 and Znt10 suggest that gene duplication event in the ZnT superfamily gene probably occurred in the later phase of evolution when individual specificities of the distinguished ZnT subgroups were already formed.