Suchi Srivastava

Plant growth-promoting bacteria Bacillus amyloliquefaciens NBRISN13 modulates gene expression profile of leaf and rhizosphere community in rice during salt stress.

Growth and productivity of rice and soil inhabiting microbial population is negatively affected by soil salinity. However, some salt resistant, rhizosphere competent bacteria improve plant health in saline stress. Present study evaluated the effect of salt tolerant Bacillus amyloliquefaciens NBRISN13 (SN13) inoculation on rice plants in hydroponic and soil conditions exposed to salinity. SN13 increased plant growth and salt tolerance (NaCl 200 mM) and expression of at least 14 genes under hydroponic and soil conditions in rice. Among these 14 genes 4 (NADP-Me2, EREBP, SOSI, BADH and SERK1) were up-regulated and 2 (GIG and SAPK4) repressed under salt stress in hydroponic condition. In greenhouse experiment, salt stress resulted in accumulation of MAPK5 and down-regulation of the remaining 13 transcripts was observed. SN13 treatment, with or without salt gave similar expression for all tested genes as compared to control. Salt stress caused changes in the microbial diversity of the rice rhizosphere and stimulated population of betaine-, sucrose-, trehalose-, and glutamine-utilizing bacteria in salt-treated rice rhizosphere (SN13 + salt). The observations imply that SN13 confers salt tolerance in rice by modulating differential transcription in a set of at least 14 genes. Stimulation of osmoprotectant utilizing microbial population as a mechanism of inducing salt tolerance in rice is reported for the first time in this study to the best of our knowledge.

Gene expression profiling through microarray analysis in Arabidopsis thaliana colonized by Pseudomonas putida MTCC5279, a plant growth promoting rhizobacterium

Plant growth promotion is a multigenic process under the influence of many factors; therefore an understanding of these processes and the functions regulated may have profound implications. Present study reports microarray analysis of Arabidopsis thaliana plants inoculated with Pseudomonas putida MTCC5279 (MTCC5279) which resulted in significant increase in growth traits as compared with non-inoculated control. The gene expression changes, represented by oligonucleotide array (24652 genes) have been studied to gain insight into MTCC5279 assisted plant growth promotion in Arabidopsis thaliana. MTCC5279 induced upregulated Arabidopsis thaliana genes were found to be involved in maintenance of genome integrity (At5g20850), growth hormone (At3g23890 and At4g36110), amino acid synthesis (At5g63890), abcissic acid (ABA) signaling and ethylene suppression (At2g29090, At5g17850), Ca+2 dependent signaling (At3g57530) and induction of induced systemic resistance (At2g46370, At2g44840). The genes At3g32920 and At2g15890 which are suggested to act early in petal, stamen and embryonic development are among the downregulated genes. We report for the first time MTCC5279 assisted repression of At3g32920, a putative DNA repair protein involved in recombination and DNA strand transfer in a process of rapid meiotic and mitotic division.

Construction of genetic linkage map of the medicinal and ornamental plant Catharanthus roseus

An integrated genetic linkage map of the medicinal and ornamental plant Catharanthus roseus, based on different types of molecular and morphological markers was constructed, using a F2 population of 144 plants. The map defines 14 linkage groups (LGs) and consists of 131 marker loci, including 125 molecular DNA markers (76 RAPD, 3 RAPD combinations; 7 ISSR; 2 EST-SSR from Medicago truncatula and 37 other PCR based DNA markers), selected from a total of 472 primers or primer pairs, and six morphological markers (stem pigmentation, leaf lamina pigmentation and shape, leaf petiole and pod size, and petal colour). The total map length is 1131.9 cM (centiMorgans), giving an average map length and distance between two markers equal to 80.9 cM and 8.6 cM, respectively. The morphological markers/genes were found linked with nearest molecular or morphological markers at distances varying from 0.7 to 11.4 cM. Linkage was observed between the morphological markers concerned with lamina shape and petiole size of leaf on LG1 and leaf, stem and petiole pigmentation and pod size on LG8. This is the first genetic linkage map of C. roseus.

Regulation of stipule development by COCHLEATA and STIPULE-REDUCED genes in pea Pisum sativum

Pisum sativum L., the garden pea crop plant, is serving as the unique model for genetic analyses of morphogenetic development of stipule, the lateral organ formed on either side of the junction of leafblade petiole and stem at nodes. The stipule reduced (st) and cochleata (coch) stipule mutations and afila (af), tendril-less (tl), multifoliate-pinna (mfp) and unifoliata-tendrilledacacia (uni-tac) leafblade mutations were variously combined and the recombinant genotypes were quantitatively phenotyped for stipule morphology at both vegetative and reproductive nodes. The observations suggest a role of master regulator to COCH in stipule development. COCH is essential for initiation, growth and development of stipule, represses the UNI-TAC, AF, TL and MFP led leafblade-like morphogenetic pathway for compound stipule and together with ST mediates the developmental pathway for peltate-shaped simple wild-type stipule. It is also shown that stipule is an autonomous lateral organ, like a leafblade and secondary inflorescence.

Chlorella vulgaris and Pseudomonas putida interaction modulates phosphate trafficking for reduced arsenic uptake in rice (Oryza sativa L.)

Rice grown in arsenic (As) contaminated areas contributes to high dietary exposure of As inducing multiple adverse effects on human health. The As contamination and application of phosphate fertilizers during seedling stage creates a high P and As stress condition. The flooded paddy fields are also conducive for algal growth and microbial activity. The present study proposes potential role of microalgae, Chlorella vulgaris (CHL) and bacteria, Pseudomonas putida (RAR) on rice plant grown under excess As and phosphate (P) conditions. The results show synchronized interaction of CHL + RAR which, reduces As uptake through enhanced P:As and reduced As:biomass ratio by modulating P trafficking. Gene expression analysis of different phosphate transporters exhibited correlation with reduced As uptake and other essential metals. The balancing of reactive oxygen species (ROS), proline accumulation, hormone modulation, and As sequestration in microbial biomass were elucidated as possible mechanisms of As detoxification. The study concludes that RAR and CHL combination mitigates the As stress during P-enriched conditions in rice by: (i) reducing As availability, (ii) modulating the As uptake, and (iii) improving detoxification mechanism of the plant. The study will be important in assessing the role and applicability of P solubilizing biofertilizers in these conditions.

Mycoremediation Mechanisms for Heavy Metal Resistance/Tolerance in Plants

Environmental pollution is an ever-increasing problem being faced by the world in the present era. Soil pollution is increasing, owing to dumping of all kinds of wastes, mining and using of agrochemicals and other anthropogenic activities. These pollutants include many recalcitrant organic compounds, e-wastes, isotopic wastes and heavy metals. Heavy metals are essentially polluting agricultural fields and thus affect productivity and quality of the produce. Accumulation of these toxic metals in plants leads to their subsequent transfer and biomagnification in the food chain. Therefore, their toxicity is an area of concern for ecological, evolutionary, nutritional and environmental reasons. Several strategies are being employed for remediation of agricultural soils, mycoremediation being one of them. Mycoremediation is an eco-friendly ‘green-clean’ technology that has tremendous potential to be utilized in the cleaning up of heavy metals and organic pollutants. Association of plant and fungi can detoxify toxic metals, translocate and accumulate them in the above-ground biomass, which has to be then harvested for metal recovery. Despite tremendous potential for the application of mycoremediation in the cleaning up of contaminated soil, sediment and water, it has not been commercialized and used extensively on a large scale. The present chapter discusses the strategies and applicability of mycoremediation mechanisms for heavy metal resistance/tolerance in plants.

Assessment of Anticancer Properties of Betelvine

Betelvine (Piper betle) leaves are known for its medicinal properties since 600 AD practiced in Ayurvedic system of medicine. It is a cash crop for many Southeast Asian countries and is, therefore, also known as “Green Gold.” Widely consumed as masticator, betelvine leaves are a rich source of phenolic compounds having antiproliferative, antimutagenic, antibacterial, and antioxidant properties. The Piper betel leaf (PBL) extract is used as an antiseptic in cuts and wounds, is used as a diuretic, helps in digestion, and treats boils, conjunctivitis, stomach problems, hysteria, itches, leucorrhea, and ringworm. Also, the PBL extract is used as adjunct in Ayurvedic medicines, and the essential oil obtained from the betelvine leaves has antimicrobial and antiprotozoal activities. The high amounts of phenolic compounds present in betelvine leaf extract are of antioxidant nature which plays a key role to serve several medicinal properties. Apart from these medicinal properties reported since Ayurvedic times, modern researches have proved them to bear anticancer properties too. The compounds that confer the anticancer activity to betelvine leaves include antioxidant compounds such as eugenol, hydroxychavicol, β-carotene, and ascorbic acid, all of which are known for scavenging free radicals, thereby preventing cellular damages. In the present chapter, we have discussed the advances in betelvine research in the field of cancer as a cancer suppressor, killing agent for cancer cells, as nutraceutical and other medicinal properties helpful in cancer therapy.

Reduced cell wall degradation plays a role in cow dung-mediated management of wilt complex disease of chickpea

Chickpea, a major pulse crop, is highly prone to a devastating wilt disease commonly caused by the complex interaction of soilborne fungal pathogens of the genus Fusarium, Rhizoctonia and Sclerotinia. These pathogens collectively cause both superficial and sunken lesions resulting in symptoms like wilting and yellowing causing plant losses at seedling stage and become a major limiting factor for its growth and yield. Earlier studies demonstrated the role of composted mixture in protection against soilborne pathogens. However, there is paucity of substantial evidence for the mechanism of protection. The present study predicts the probable mechanism of cow dung-mediated reduction of wilt in Cicer arietinum. Cow dung-coated seeds sown in presence of mixture of fungi (FCD) could reduce the activities of cell wall-degrading enzymes produced by plant roots in response to pathogens, which were otherwise higher in mixture of wilt complex fungi/pathogens (FUN) treatment. Reduction in transcript accumulation of related genes followed by histological studies showed intercellular fungal colonization in FUN treatment, whereas it was undetected in FCD. Results indicate that cow dung treatment of chickpea seeds reduces activities of the cell wall-degrading enzymes in a transcriptionally regulated manner, which in turn function as biocontrol measure for disease.

Kinetics and Mechanism of Silver Ion Catalysed Oxidation of Diols with Terminal Hydroxyl Groups by Peroxydisulphate Ion(l)

Kinetic study of Ag+ catalysed oxidation of diols having term¬inal hydroxyl groups viz. propane-1, 3-diol, butane-1, 4-diol, pen- tane-1, 5-diol, and hexane-1, 6-diol by peroxydisulphate ion reveals that these reactions, unlike other diols studied so far, do not fol¬low simple first order kinetics. Each reaction follows first order behaviour in the initial stages, followed by half order inhibition. However, first order specific rate for the initial stage has been found to vary with initial concentration of the reactants. The negative salt effect is of primary exponential type in each case. Various thermodynamic parameters have been evaluated. On the basis of a detailed kinetic study of the initial stage of the reaction (before the onset of inhibition) and product identification, a gen¬eral mechanism for these reactions has been proposed and the rate law derived therefrom. Incidentally, this study has provided a simpler method for the synthesis of corresponding hydroxyaldehydes.