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Brassinosteroids (BRs) are steroidal phytohormones that play a multitasking role during the growth and development period as well as stress responses. Plant mutants in BR production or defective signaling result in various physiological as well as phenotypical abnormalities. Presently, various studies have highlighted stress tolerance induction by brassinosteroids in various plant species indicating BRs as a broad spectrum key regulator participating in various molecular processes. The present chapter highlights the studies on BRs regarding their potent role in inducing stress tolerance during viral, fungal, bacterial or nematode attacks in plants. BR's multifaceted role during stress and its potential cross-talk with other phytohormones in adapting and ameliorating the stress have been critically analyzed. The divergence in dosage of BR analogs and their mode of application for management of stress are also discussed which serves as a future area of interest in challenging agriculture, thereby highlighting relevant knowledge gaps.

A chitinolytic bacterium Chitinophaga sp. S167 producing extracellular chitinases was isolated from a soil sample in India. The extracellular chitinases produced by S167 were concentrated by ammonium sulphate precipitation (AS70) and seven bands corresponding to chitinases were observed by zymography. Optimum temperature and pH of AS70 were between 40 and 45 °C and pH 6.0 respectively with high stability at 20-40 °C and pH 5-7. AS70 inhibited the growth of Fusarium oxysporum, Alternaria alternata and Cladosporium sp. in vitro. The culture conditions for the high level production of extracellular chitinases were optimized resulting in 48-folds higher chitinase production. As the combination of chitinases could be more potent in biocontrol of plant diseases, it was checked if AS70 could control postharvest fungal infection caused by Fusarium oxysporum on tomatoes. AS70 treated tomatoes showed significant lower incidence of infection (11%) by F. oxysporum as compared with 100% in the control at 5 days post inoculation. Further, AS70 caused significant mortality in second stage juveniles of root knot nematode, Meloidogyne incognita, a major agriculture pest responsible for economic losses in agriculture. This study highlights the antifungal and nematicidal activity of chitinases produced by Chitinophaga sp. S167. To the best of our knowledge, this is the first report of the biocontrol potential of the chitinases produced by Chitinophaga sp.

We report a 2-(4-amino-2-hydroxyphenyl)benzothiazole based Schiff-base, found to be sensitive to the presence of HSO4− and I− ions as demonstrated by modulation of the various photophysical properties in the presence of these ions in solution and biological enviornments (nematodes). Various spectroscopic and TD-DFT calculations have revealed that while the molecular probe detects HSO4− ions via hydrolytic cleavage and subsequent emission enhanced mechanism, the detection of I− ions is accomplished via the formation of intermolecular charge transfer complex and the subsequent heavy atom quenching mechanism. Additionally the potential of the probe for the on site detection of vapours of ethylacetate at workplaces has been demonstrated.

Polyamines are ubiquitous organic polyvalent compounds involved in regulating the plant growth and development. The present study deals with the investigation of their role in plant physiology during nematode pathogenesis. Tomato seeds var. Pusa Ruby (susceptible to nematodes) were treated with different concentrations (0.5, 0.7 and 0.9 mM) of putrescine and allowed to germinate in earthen pots. Seedlings were inoculated with second stage juveniles (J2s) of Meloidogyne incognita with 130 J2s per seedling. After 45 days of nematode inoculation, various growth parameters, stress indices, photosynthetic pigments, enzymatic and non enzymatic biochemical parameters were studied in control (C), nematode inoculated (NI) and nematode inoculated plus treated plants (NI + 0.5, NI + 0.7 and 0.9 mM). Percentage germination, number of leaves, shoot/root length, fresh shoot/root weight, and dry shoot/root weight enhanced with putrescine application whereas the number of galls, average gall index, number of egg masses and root knot nematode severity level decreased. Stress indices like H2O2 and MDA content decreased whereas proline content increased with putrescine treatment. Further, reduced specific activities of enzymes in putrescine treated infected plants and enhanced levels of non-enzymatic antioxidants depicted improved response of tomato plant during nematode stress. Thus, the polyamines were found to improve the physiological responses of tomato plant even during nematode pathogenesis.

Herein, we report a benzothiazole based probe which exhibits aggregation induced emission in mixed solvents, v/v THF : water system. The blue emission observed in the solution is ascribed to the enolic emission of the excited state intramolecular proton transfer (ESIPT) prone benzothiazole chromophore, as the aggregation induced by the protic solvent, water, is expected to restrict the phototautomerization of the probe to the keto form which generally emits in the red region. However, the green emission observed in the solid aggregated state is ascribed to its keto emission, as in the solid state the ESIPT process is activated owing to stable intramolecular hydrogen bonding, giving a keto-aggregation induced emission (AIE) coupled emission. The aggregation process is evident from the particle size and the change in morphology predicted by dynamic light scattering (DLS) and scanning electron microscopy (SEM) respectively, in the aggregated state. Interestingly, the emission in the solution, as well as the solid state, is convincingly mimicked in the fluorescence imaging of various live cancer cells and plant roots.

Brassinosteroids (BRs), a class of steroidal hormones, play diverse roles in plant growth, development, signaling and defense against various biotic and abiotic stresses. It is broad spectrum key regulator in plants that participates in various molecular processes. Exogenous application of BRs vanish various constrains in the path of agricultural development. The present book chapter highlights the interaction and crosstalk of brassinosteroids with other phytohormones such as auxins, gibberellins, jasmonic acid, abscisic acid, salicylic acid, polyamines, ethylene and strigolactones in regulation of various physiological and developmental processes in plants. Various pathways reveal the versatile role of brassinosteroids in various hormonal interactions.

Root-knot nematodes are one of the important phytoparasites that adversely affect the growth and development in plants, thus affecting its productivity. Various chemical nematicides are available commercially, having adverse effect on the environment and non-target organisms. So, it becomes necessary to explore some eco-friendly strategies to manage these parasites. Polyamines recognised as potential phytohormone, enhance the plant survival during stressful conditions. Thus, present study was undertaken to evaluate the stress protective properties of two polyamines in tomato seedlings under nematode stress. Uniform sized tomato (cv. Pusa Ruby) seeds were sterilized and treated with different concentrations (0.5, 0.7 and 0.9 mM) of two polyamines i.e. putrescine and spermine. Seeds are allowed to germinate in in-vitro conditions and subjected to nematode inoculation with second stage juveniles of Meloidogyne incognita @5J2s per seedlings after germination. Various morphological and biochemical parameters were analysed after one day of nematode inoculation. Nematode invasion alters the morphological and biochemical parameters whereas polyamines treatment restores them to control level. Significant decrease in specific activities of antioxidative enzymes viz: superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, glutathione peroxidase, polyphenol peroxidase, and pyrogallol peroxidase was observed in polyamines treated seedlings except guaiacol peroxidase and phenylalanine lyase with maximum activity change by spermine application comparing with nematode inoculated seedlings. Chlorophyll content also increases significantly with spermine treatment. Non-enzymatic antioxidants analysis also revealed the anti-stress properties of polyamines as the total phenolic, ascorbic acid content significantly increases whereas decreased glutathione content was observed with polyamine application. Results obtained from confocal microscopy also revealed the inhibition of reduced glutathione and H2O2 content in polyamine treated seedlings indicated by weak intensity of fluorescence when compared with nematode inoculated seedlings with lower intensity in spermine applied seedlings.

Plants, being sessile organisms, are challenged by variety of stresses in the form of abiotic and biotic components of environment. In such adverse conditions, plants evolve various adaptive strategies in order to survive. Among these strategies, accumulation of polyamines in plants helps to combat stress. Polyamines are ubiquitous low molecular weight compounds, which are now known to be involved in stress tolerance as suggested by various pieces of evidence during abiotic and biotic stress. The anti-stress properties of polyamines in plants are illustrated by their roles in modulation of morphological growth parameters, elevation of photosynthetic pigments, as well as declined content of stress indices, antioxidative enzymes, and non-enzymatic antioxidants content. The emerging role of polyamines in plant stress tolerance has been discussed in the present review.

Plant growth and development is under the control of mutual interactions among plant hormones. The five classical categories of plant hormones include auxins, cytokinins, gibberellins, abscisic acid and ethylene. Additionally, newer classes of plant hormones have been recognized like brassinosteroids, jasmonic acid, salicylic acid and polyamines. These hormones play significant roles in regulating the plant growth and development. Various receptors and key signaling components of these hormones have been studied and identified. At genetic level, crosstalk among the various plant hormones is found to be antagonistic or synergistic. In addition, components of signaling pathway of one plant hormone interact with the signaling components of other hormone. Thus, an attempt has been made to review the literature regarding the role of plant hormones in plant physiology and the common molecular players in their signaling and crosstalk.

Pests and pathogens have become tolerant to the use of conventional methods to improve agricultural production. This has resulted in low yields of crops worldwide. Currently, genetic engineering is being employed to enhance yields both quantitatively and qualitatively. RNA interference is one such novel cellular process in functional genomics. It is triggered by short double-stranded RNA molecules referred to as small interfering RNAs that target and degrade complementary mRNAs and are controlled by an RNA-induced silencing complex. RNAi is rapidly becoming an important methodology for analyzing sequence functions in eukaryotes and even holds promise for the development of therapeutic gene silencing. Therefore, in this chapter, an endeavor has been made to concisely consolidate the available information on RNAi, its mode of action, and its utilization in crop improvement under changing climatic conditions.