Carbohydrate content and antioxidative potential of the seed of three edible indica rice (Oryza sativa L.) cultivars

Rice (Oryza sativa L.) grains or seeds are known to lose much of their nutrient and antioxidant contents, following polishing. The current study was undertaken to evaluate and compare the carbohydrate content and antioxidant parameters in the unpolished and polished seeds of three edible indica rice cultivars, namely Swarna (SW), the most popular indica rice cultivar in India and aromatic or scented cultivars Gobindobhog (GB) and Pusa Basmati (PB). While both the sucrose and starch content was the maximum in PB seeds (both unpolished and polished), the amylose content was the highest in SW polished seeds. SW polished seeds were superior as compared to GB and PB cultivars in terms of total antioxidant capacity, DPPH radical scavenging and Fe(II) chelation potential, as well as the highest lipoxygenase (LOX) inhibition or H2O2 scavenging potential, probably due to the maximum accumulation of total phenolics and flavonoids, the two important antioxidants. The reducing power ability was, however, identical in both SW and GB polished seeds. The PB polished seeds were more potent in superoxide and hydroxyl scavenging, whereas GB in nitric oxide (NO) scavenging. The common observation noted after polishing of seeds was the reduction in the level of carbohydrates and antioxidant potential, though the extent of reduction varied in the three cultivars. The only exception was GB, where there was no alteration in NO scavenging potential even after polishing. Our study showed the better performance of SW polished seeds with respect to higher amylose content and majority of the tested parameters governing antioxidant capacity and radical scavenging potential, thus highlighting the greater dietary significance of SW over the other two cultivars.     

The segregation of Escherichia coli minichromosomes constructed in vivo by recombineering

Circularized regions of the chromosome containing the origin of replication, oriC, can be maintained as autonomous minichromosomes, oriC plasmids. We show that oriC plasmids containing precise, pre-determined segments of the chromosome can be generated by a simple in vivo recombineering technique. We generated two such plasmids carrying fluorescent markers. These were transferred to a recipient strain with a different fluorescent marker near the chromosomal copy of oriC. Thus the fates of the oriC plasmid and chromosomal origins could be followed independently in living cells by fluorescence microscopy. In contrast to a previous report, we show that there is a strong tendency of oriC plasmid copies to accumulate at the cell center as a single or double focus at the plane of cell division. This is not simply due to exclusion from the nucleoid space but rather appears to be a specific recognition and retention of the plasmid by some central-located cell site.     

Spermidine and abscisic acid-mediated phosphorylation of a cytoplasmic protein from rice root in response to salinity stress

Importance of higher polyamines, spermidine, and spermine, in relation to the mechanism and adaptation to combat abiotic stress has been well established in cereals. Owing to their polycationic nature at physiological pH, polyamines bind strongly to negative charges in cellular components such as nucleic acids, various proteins, and phospholipids. To study the physiological role of polyamine during salinity stress, phosphorylation study was carried out in cytosolic soluble protein fraction isolated from the roots of salt tolerant (Nonabokra) and salt sensitive (M-1-48) rice cultivars treated with none (control), NaCl (150 mM, 16 h), spermidine (1 mM, 16 h) or with abscisic acid (100 μM, 16 h). A calcium independent auto regulatory 42 kDa protein kinase was found to phosphorylate myelin basic protein and casein but not histone. Interestingly, this was the only protein to be phosphorylated in root cytosolic fraction during NaCl/abscisic acid/spermidine treatment indicating its importance in salinity mediated signal transduction. This is the first report of polyamine as well as abscisic acid induced protein kinase activity in rice root in response to salinity stress.     

Non-enzymatic antioxidative defence in drought-stressed mulberry (<Emphasis Type="Italic">Morus indica</Emphasis> L.) genotypes

The present study investigated drought-induced responses of non-enzymatic antioxidants in four diverse mulberry genotypes (Morus indica L. S-36, M-5, MR-2 and V-1). Inside the glasshouse, potted plants were subjected to four water regimes for 75 days: (a) control: pots maintained at 100% pot water holding capacity (PC) (b) low water stress: 75% PC (c) medium water stress: 50% PC and (d) high water stress: 25% PC. Photosynthetic leaf gas exchange and non-enzymatic antioxidants including α-tocopherol, ascorbic acid (AA), glutathione, proline and total carotenoids were measured in leaves at regular intervals. Amongst all, V-1 was relatively drought tolerant and showed exceeded accumulation of α-tocopherol and AA-glutathione pool in association with higher carotenoids and proline contents. Susceptible S-36, M-5 and MR-2 could not induce any significant up-regulation in AA-glutathione pool leading to endogenous loss of α-tocopherol and more lipid peroxidation. Reactive oxygen species (ROS) like hydrogen peroxide (H₂O₂) and superoxide (O₂ ^{· ?}) showed apparent accumulation in water-stressed leaves and significantly contributed to lipid peroxidation in susceptible genotypes when compared to V-1. Our study demonstrated that proline, AA and glutathione were the major non-enzymatic antioxidants in mulberry with α-tocopherol and carotenoids as good additional indicators for drought stress tolerance. These non-enzymatic antioxidants can cumulatively render effective protection against oxidative damage and can be considered as reliable markers for screening drought-tolerant mulberry genotypes.     

Detoxification potential and expression analysis of eutypine reducing aldehyde reductase (VrALR) during progressive drought and recovery in Vigna radiata (L.) Wilczek roots

Generation of reactive oxygen species (ROS) in plants is an inevitable consequence of adverse environmental cues and the ability to detoxify deleterious by-products of ROS-mediated oxidation reactions reflect an important defence strategy to combat abiotic stress. Here, we have cloned the eutypine reducing aldehyde reductase gene (VrALR) from Vigna radiata (L.) Wilczek roots. We have expressed and purified the VrALR protein and analyzed its enzyme kinetic parameters and catalytic efficiency with three different substrates to confirm its identity. The functional characterization of this enzyme was unravelled through heterologous expression of the gene in Escherichia coli BL21 and an oxidative stress-sensitive Saccharomyces cerevisiae mutant strain, W3O3-1-A. Finally, the endogenous VrALR enzyme activity and the mRNA expression patterns of the VrALR gene in the roots of V. radiata in response to progressive drought stress in vivo was studied to correlate the ROS-detoxifying role of this important enzyme under the influence of progressive drought stress. Our results, for the first time, demonstrate that eutypine reducing VrALR provides varying degree of stress tolerance in bacteria, yeast systems and also plays a promising protective role against oxidative stress in V. radiata roots during gradual water deprivation. The present study provides an unequivocal evidence to understand the crucial role of aldehyde reductase ROS-detoxifying system which is highly essential for developing stress tolerance in economically important crop plants.     

Structural diversity in bacterial ribosomes: mycobacterial 70S ribosome structure reveals novel features

Here we present analysis of a 3D cryo-EM map of the 70S ribosome from Mycobacterium smegmatis, a saprophytic cousin of the etiological agent of tuberculosis in humans, Mycobacterium tuberculosis. In comparison with the 3D structures of other prokaryotic ribosomes, the density map of the M. smegmatis 70S ribosome reveals unique structural features and their relative orientations in the ribosome. Dramatic changes in the periphery due to additional rRNA segments and extra domains of some of the peripheral ribosomal proteins like S3, S5, S16, L17, L25, are evident. One of the most notable features appears in the large subunit near L1 stalk as a long helical structure next to helix 54 of the 23S rRNA. The sharp upper end of this structure is located in the vicinity of the mRNA exit channel. Although the M. smegmatis 70S ribosome possesses conserved core structure of bacterial ribosome, the new structural features, unveiled in this study, demonstrates diversity in the 3D architecture of bacterial ribosomes. We postulate that the prominent helical structure related to the 23S rRNA actively participates in the mechanisms of translation in mycobacteria.     

Alternate glucocorticoid receptor ligand binding structures influence outcomes in an in vivo tissue regeneration model

Since their characterization, glucocorticoids (GCs), the most commonly prescribed immunomodulatory drugs, have undergone numerous structural modifications designed to enhance their activity. In vivo assessment of these corticosteroid analogs is essential to understand the difference in molecular signaling of the ligands that share the corticosteroid backbone. Our research identified a novel function of GCs as modulators of tissue regeneration and demonstrated that GCs activate the glucocorticoid receptor (GR) to inhibit early stages of tissue regeneration in zebrafish (Danio rerio). We utilized this phenomenon to assess the effect of different GC analogs on tissue regeneration and identified that some GCs such as beclomethasone dipropionate (BDP) possess inhibitory properties, while others, such as dexamethasone and hydrocortisone have no effect on regeneration. We performed in silico molecular docking and dynamic studies and demonstrated that type and size of substitution at the C17 position of the cortisol backbone confer a unique stable conformation to GR on ligand binding that is critical for inhibitory activity. In the field of tissue regeneration, our study is one of the first Structure Activity Relationship (SAR) investigations performed in vertebrates demonstrating that the in vivo tissue regeneration model is a powerful tool to probe structure function relationships, to understand regenerative biology, and to assist in rational drug design.     

Human Endogenous Retrovirus Expression Is Inversely Associated with Chronic Immune Activation in HIV-1 Infection

Human endogenous retroviruses (HERV) are remnants of ancestral retroviral infections integrated into the germ line, and constitute approximately 8% of the genome. Several autoimmune disorders, malignancies, and infectious diseases such as HIV-1 are associated with higher HERV expression. The degree to which HERV expression in vivo results in persistent inflammation is not known. We studied the association of immune activation and HERV-K expression in 20 subjects with chronic, untreated progressive HIV-1 infection and 10 HIV-1 negative controls. The mean HERV-K gag and env RNA expression level in the HIV-1 infected cohort was higher than in the control group (p = 0.0003), and was negatively correlated with the frequency of activated CD38+HLA-DR+CD4+ T cells (Rho = −0.61; p = 0.01) and activated CD38+HLA-DR+CD8+ T cells (Rho  = −0.51; p = 0.03). Although HIV-infected persons had higher levels of HERV-K RNA expression (as expected), the level of RNA expression was negatively associated with level of T cell activation. The mechanism for this unexpected association remains to be defined.