Synthesis and evaluation of in vitro antioxidant capacities of some benzimidazole derivatives

New, except 1d, melatonin analogue benzimidazole derivatives were synthesized and characterized in the present study. The potential role of melatonin as an antioxidant by scavenging and detoxifying ROS raised the possibility that compounds that are analogous to melatonin can also be used for their antioxidant properties. Therefore the antioxidant effects of the newly synthesized compounds were investigated in vitro by means of their inhibitory effect on hydrogen peroxide-induced erythrocyte membrane lipid peroxidation (EMLP) and on various erythrocyte antioxidant enzymes viz. superoxide dismutase (SOD), catalase (CAT) and glucose-6-phosphate dehydrogenase (G6PD). The synthesized benzimidazole derivatives showed remarkable antioxidant activity in vitro in the H₂O₂-induced EMLP system. Furthermore their effects on various antioxidant enzymes are discussed and evaluated from the perspective of structure- activity relationships.     

Local host ant specificity of Phengaris (Maculinea) teleius butterfly,an obligatory social parasite of Myrmica ants

1. Phengaris butterflies are obligatory social parasites of Myrmica ants. Early research suggested that there is a different Myrmica host species for each of the five European Phengaris social parasites, but more recent studies have shown that this was an oversimplification. 2. The pattern of host ant specificity within a Phengaris teleius metapopulation from southern Poland is reported. A combination of studying the frequency distribution of Phengaris occurrence and morphometrics on adult butterflies were used to test whether use of different host species is reflected in larval development. 3. Phengaris teleius larvae were found to survive in colonies of four Myrmica species: M. scabrinodis, M. rubra, M. ruginodis, and M. rugulosa. Myrmica scabrinodis was the most abundant species under the host plant but the percentage of infested nests was similar to other host ant species at two sites and lower in comparison to nests of M. rubra and M. ruginodis at the other two sites. Morphometric measurements of adult butterflies reared by wild colonies of M. scabrinodis and M. ruginodis showed that wing size and number of wing spots were slightly greater for adults eclosing from nests of M. ruginodis. 4. Our results suggest that P. teleius in the populations studied is less specialised than previously suggested. The results are consistent with the hypothesis that P. teleius is expected to be the least specific of the European Phengaris species, as it has the largest and best defended fourth‐instar caterpillars and, as a predatory species, it spends less time in the central larval chambers of the host colonies. The fact that individuals reared by M. ruginodis had wider hind wings may suggest that P. teleius had better access to resources in M. ruginodis than in M. scabrinodis colonies.     

Chemical signaling under abiotic stress environment in plants

Many chemicals are critical for plant growth and development and play an important role in integrating various stress signals and controlling downstream stress responses by modulating gene expression machinery and regulating various transporters/pumps and biochemical reactions. These chemicals include calcium (Ca²⁺), cyclic nucleotides, polyphosphoinositides, nitric oxide (NO), sugars, abscisic acid (ABA), jasmonates (JA), salicylic acid (SA) and polyamines. Ca²⁺ is one of the very important ubiquitous second messengers in signal transduction pathways and usually its concentration increases in response to the stimuli including stress signals. Many Ca²⁺ sensors detect the Ca²⁺ signals and direct them to downstream signaling pathways by binding and activating diverse targets. cAMP or cGMP protects the cell with ion toxicity. Phosphoinositides are known to be involved both in transmission of signal across the plasma membrane and in intracellular signaling. NO activates various defense genes and acts as a developmental regulator in plants. Sugars affect the expression of many genes involved in photosynthesis, glycolysis, nitrogen metabolism, sucrose and starch metabolism, defense mechanisms and cell cycle regulation. ABA, JA, SA and polyamines are also involved in many stress responses. Cross-talk between these chemical signaling pathways is very common in plant responses to abiotic and bitotic factors. In this article we have described the role of these chemicals in initiating signaling under stress conditions mainly the abiotic stress.Key words: ABA, abiotic stress, Ca²⁺ binding proteins, calcium signaling, cyclic nucleotides, nitric oxide, phosphoinositides signaling, signal transduction, sugar signaling     

Thermo and pH stable ATP-independent chaperone activity of heat-inducible Hsp70 from Pennisetum glaucum

Heat shock proteins (Hsps) are a class of molecular chaperones that play an essential role in preserving cellular functions under stressful conditions. The over production of recombinant proteins often causes cellular stress that results in aggregation/misfolding of proteins, which sometimes leads to the formation of inclusion bodies. Here we report the cloning and characterization of heat-inducible PgHsp70 from Pennisetum glaucum, a heat and drought tolerant plant that showed stability and chaperone activity at elevated temperatures. The predicted amino acid sequence of PgHsp70 revealed a high homology with Hsp70 from other plants, and the overall 3D structure homology modeling is similar to that of the constitutively expressed bovine cytosolic Heat Shock Cognate (HSC)-70. The purified recombinant protein had an apparent molecular mass of 70 kDa and displayed optimal chaperone activity at 50°C, and pH 8.0. Under these conditions, the T_1/2 of PgHsp70 increased from 10 to 15 h in the presence of glycerol. The PgHsp70 exhibited a higher chaperone activity towards glutamate dehydrogenase than alcohol dehydrogenase. The expression of recombinant carbonic anhydrase (CA ) in E. coli in a catalytically active soluble form rather than in inclusion bodies was made feasible by co-expression of PgHsp70. Circular dichroism (CD) studies of the recombinant PgHsp70 did not reveal any discernible changes in the α-helix content, with increase in temperature from 35 to 85°C, thus suggesting a critical role of α-helix content in maintaining the chaperone activity.Key words: abiotic stress, carbonic anhydrase, chaperone, circular dichroism, heat shock proteins (Hsp70), Pennisetum glaucum, pH stable     

Deciphering the regulatory mechanisms of abiotic stress tolerance in plants by genomic approaches

Environmental constraints that include abiotic stress factors such as salt, drought, cold and extreme temperatures severely limit crop productivity. Improvement of crop plants with traits that confer tolerance to these stresses was practiced using traditional and modern breeding methods. Molecular breeding and genetic engineering contributed substantially to our understanding of the complexity of stress response. Mechanisms that operate signal perception, transduction and downstream regulatory factors are now being examined and an understanding of cellular pathways involved in abiotic stress responses provide valuable information on such responses. This review presents genomic-assisted methods which have helped to reveal complex regulatory networks controlling abiotic stress tolerance mechanisms by high-throughput expression profiling and gene inactivation techniques. Further, an account of stress-inducible regulatory genes which have been transferred into crop plants to enhance stress tolerance is discussed as possible modes of integrating information gained from functional genomics into knowledge-based breeding programs. In addition, we envision an integrative genomic and breeding approach to reveal developmental programs that enhance yield stability and improve grain quality under unfavorable environmental conditions of abiotic stresses.