Indu Sharma

Differential regulation of microRNAs in response to osmotic, salt and cold stresses in wheat

MicroRNAs (miRNAs) are tiny non-coding regulatory molecules that modulate plant’s gene expression either by cleaving or repressing their mRNA targets. To unravel the plant actions in response to various environmental factors, identification of stress related miRNAs is essential. For understanding the regulatory behaviour of various abiotic stresses and miRNAs in wheat genotype C-306, we examined expression profile of selected conserved miRNAs viz. miR159, miR164, miR168, miR172, miR393, miR397, miR529 and miR1029 tangled in adapting osmotic, salt and cold stresses. The investigation revealed that two miRNAs (miR168, miR397) were down-regulated and miR172 was up-regulated under all the stress conditions. However, miR164 and miR1029 were up-regulated under cold and osmotic stresses in contrast to salt stress. miR529 responded to cold alone and does not change under osmotic and salt stress. miR393 showed up-regulation under osmotic and salt, and down-regulation under cold stress indicating auxin based differential cold response. Variation in expression level of studied miRNAs in presence of target genes delivers a likely elucidation of miRNAs based abiotic stress regulation. In addition, we reported new stress induced miRNAs Ta-miR855 using computational approach. Results revealed first documentation that miR855 is regulated by salinity stress in wheat. These findings indicate that diverse miRNAs were responsive to osmotic, salt and cold stress and could function in wheat response to abiotic stresses.

Solid state chemistry of Ruddlesden-Popper type complex oxides

Various criteria of formation of perovskites and K2NiF4-type compounds, which are the end members of homologous Ruddlesden-Popper series of phases, have been discussed. RP-phases show some general trends in their physical properties. Literature survey of the formation of these phases, their properties, and effect of oxygen stoichiometry and doping is presented. Some conditions for their synthesis are also described.

Effect of substitution of magnetic rare earths for la on the structure, electric transport and magnetic properties of La2SrFe2O7

Abstract Ln2SrFe2O7, (Ln=La, Nd, Gd and Dy) phases have been prepared by the ceramic method. The powder X-ray diffraction studies show that these phases crystallize with tetragonal unit cell in the space group I 4/mmm. The unit cell dimensions decrease with substitution of Nd, Gd, and Dy for La, with more pronounced change in c which is attributed to shrinkage of the interlayer distances. Magnetic studies show that the Weiss constant (θ) increases with substitution of the rare earths in the order Dy>Gd>Nd, which is the result of increase in the inter-layer ferromagnetic interactions due to decrease in c-axis. The Weiss constants suggest that La2SrFe2O7 and Nd2SrFe2O7 are antiferromagnetic, while the Gd and Dy containing phases are ferromagnetic. The increased 3D character in the rare earth substituted phases results in a decrease in the electrical resistivity in the order Dy>Gd>Nd.

Solid state synthesis and structural refinement of polycrystalline La x Ca1−x TiO3 ceramic powder

Perovskite structure based ceramic precursors have a characteristic property of substitution in the “A” site of the ABO3 structure. This makes them a potential material for nuclear waste management in synthetic rock (SYNROC) technology. In order to simulate the mechanism of rare earth fixation in perovskite, Lax Ca1−xTiO3 (wherex = 0.05) has been synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and La as starting materials. Solid state synthesis has been carried out by repeated pelletizing and sintering the finely powdered oxide mixture in a muffle furnace at 1050°C. The ceramic phase has been characterized by its powder diffraction pattern. Step analysis data has been used to determine the structure of solid solution of lanthanum substituted calcium titanate. The SEM and EDAX analyses also confirm that the CaTiO3 can act as a host for lanthanum. X-ray data has been interpreted using CRYSFIRE and POWDERCELL softwares. Theh, k, l values for different lattice planes have been generated from the experimental data. The lanthanum substituted perovskite crystallizes in orthorhombic symmetry with space groupP n m a (#62). Following unit cell parameters have been calculated:a = 5.410,b = 7.631,c = 5.382. The calculated and observed values of corresponding intensities, 2θ, and density show good agreement. GSAS based calculation for bond distances Ti-O, Ca-O, La-O and bond angles Ti-O-Ca, Ca-O-Ca, La-O-Ti have been reported.

Synthesis, structure, electric transport and magnetic properties of Sr2LaMnFeO7 and Sr2LaMn1.5Fe0.5O7

Abstract New RP-type phases Sr 2 LaMnFeO 7 and Sr 2 LaMn 1.5 Fe 0.5 O 7 have been synthesised by the ceramic method. Rietveld profile analysis shows that these phases crystallize with tetragonal unit cell in the space group I 4/ mmm . Sr 2 LaMn 1.5 Fe 0.5 O 7 shows insulator–metal (I–M) transition at low temperatures, the phenomenon often associated with giant magnetoresistance. 3D variable range hopping governs the electrical conduction in the insulator region above the I–M transition temperature. Magnetic studies suggest that the Curie temperature ( θ ) is positive.

Physiological traits associated with heat tolerance in bread wheat (Triticum aestivum L.)

Field experiments for evaluating heat tolerance-related physiological traits were conducted for two consecutive years using a mapping population of recombinant inbred lines (RILs) from the cross RAJ4014/WH730. Chlorophyll content (Chl) and chlorophyll fluorescence (CFL) were recorded under timely sown (TS) and late sown (LS) conditions. Late sowing exposes the terminal stage of plants to high temperature stress. Pooled analysis showed that CFL and Chl differed significantly under TS and LS conditions. The mean value of CFL (Fv/Fm) and Chl under both timely and late sown conditions were used as physiological traits for association with markers. Regression analysis revealed significant association of microsatellite markers viz., Xpsp3094 and Xgwm131 with coefficients of determination (R2) values for CFL (Fv/Fm) and Chl as 12 and 8xa0%, respectively. The correlation between thousand grain weight (TGW) with Chl and CFL were 14 and 7xa0% and correlation between grain wt./spike with Chl and CFL were 15 and 8xa0%, respectively. The genotypes showing tolerance to terminal heat stress as manifested by low heat susceptibility index (HSIu2009=u20090.43) for thousand grain weight, were also found having very low Chl, HSI (−0.52). These results suggest that these physiological traits may be used as a secondary character for screening heat-tolerant genotypes.

Synthesis, structure and elementary properties of Sr3MnRuO7

Abstract A new RP-type phase Sr 3 MnRuO 7 has been prepared by a standard ceramic method and its crystal structure has been determined by the powder X-ray diffraction analysis. The phase crystallizes in a tetragonal unit cell in space group I4/mmm . Electrical resistivity and magnetic susceptibility studies show that it undergoes an insulator–metal transition and is accompanied by a ferromagnetic transition, the behaviour suggestive of giant magnetoresistance (GMR).

Deciphering the dynamics of changing proteins of tolerant and intolerant wheat seedlings subjected to heat stress.

Indulgence of heat defense mechanism is crucial to allay undesirable effects by developing significant heat tolerant plants. Translation of heat stress related genes into proteins is a key tolerance strategy tailored by plants. In order to understand the possible mechanisms of heat tolerance in wheat at proteomic level, two wheat genotypes (WH 730-heat tolerant; Raj 4014-heat intolerant) along with their 10 extreme recombinant inbred lines (RILs) were exposed to heat stress (35xa0°C for 6xa0h) to identify important stress related proteins. 2-DE coupled with MALDI TOF/TOF of wheat seedlings revealed 14 differentially regulated protein spots. Compared to Raj 4014, 3 proteins viz. Rubisco activase A, Con A and PEP carboxylase 1 were differentially regulated only in WH 730 implying their practical role in heat tolerance. Above and beyond, increased expression of cytochrome b6f complex and catalase in tolerant RIL population signifies their role in accelerated electron flow during heat stress to cope up with the stress. Our results suggests that, compared to intolerant parent and RILs, tolerant parent and RILs might be actively modulating protein involved in photosynthesis, signal transduction and defense which signifies the activation of adaptation mechanism under heat stress.

Trait analysis, diversity, and genotype x environment interaction in some wheat landraces evaluated under drought and heat stress conditions

Both drought and heat stress are responsible for decline in wheat (Triticum aestivum L.) production in many regions of the world. Intergovernmental Panel on Climate Change (IPCC) has predicted increase in these areas. Development of heat and drought tolerant genotypes is on priority. Landraces are unexploited genetic resources for various agronomic traits contributing tolerance to abiotic stress. Twenty-five wheat genotypes were evaluated in irrigated timely, rainfed timely and irrigated late sown conditions for 2 yr using 10 agronomic traits for their response to drought and heat stress and four stress indices (stress susceptibility index, stress tolerance index, mean productivity, and stress tolerance) were calculated. Variability averaged over traits was highest under rainfed conditions. Grain yield, plant height, and productive tillers were more sensitive and test grain weight as tolerant under drought. Under heat stress grain yield, grain weight, test grain weight and phenological traits were more sensitive. Productive tillers and grain number per spike were identified as important selection parameters for drought and grain weight (per spike and test grain weight) as for heat tolerance. Genotypes IC 321987, IC 322005, IC 138852, IC 138870 adapted to stressed environments or genotypes CPAN 4079 and NEPAL 38 stable over all environments can be used for introgression of the stress tolerance in elite cultivars.

Mechanism of formation of Cu(II) carboxylates in the solid state 1. Kinetics of reactions between benzoic acid, salicylic acid and CuCO3 Cu(OH)2

The kinetic data for reactions between aromatic acids, i.e. benzoic acid, salicylic acid and basic copper carbonate in the solid state have been recorded. The measurements have been made at various temperatures for fixed sizes of the particles at constant compression. The products are characterised by infrared and reflectance spectra. The reactions are diffusion-controlled with activation energy of 71.8 and 115.0±5 kJ mol−1 for the formation of Cu(II) benzoate and Cu(II) salicylate respectively.