Browsing by Author "R. Saini"

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Possibility of hydrological connectivity between Manasarovar Lake and Gangotri Glacier
(Indian Academy of Sciences, 2019) S.P. Rai; D. Singh; R. Saini; D.S. Rathore; S. Kumar; S.K. Jain; N. Pant
Considering the hydrological and religious significance of the Ganga River and the Manasarovar Lake in India, the present study has been devised to investigate the data related to the place of origin of the Ganges and to investigate the likely connection between waters of the two systems. Satellite data was employed to develop maps and find out the possibility of surface connectivity, whereas isotopic and chemical data, obtained from the field samplings and the published research literatures were used to investigate the possibility of subsurface connectivity of the Gangotri Glacier water with that of the Manasarovar Lake. Topographically, both the water systems are located in different catchment zones, separated by high mountain ridges; rejecting any possibility for the surface connectivity. Similarly, there are significant variations in isotopic and physiochemical properties of the water, suggesting no possibility of surface or sub-surface connectivity between water of the two systems. © 2019, Indian Academy of Sciences.
Role of secondary metabolites in plant defense mechanisms: a molecular and biotechnological insights
(Springer Science and Business Media B.V., 2024) R. Upadhyay; R. Saini; P.K. Shukla; K.N. Tiwari
The plants produce secondary metabolites (SMs) as defence compounds against both abiotic and biotic stresses. These stresses instigate the secretion and release of SMs by up or down-regulating the concerned genes involved in their synthesis. The secretion of SMs varies with the plant's genetic constitution and accordingly-they are susceptible or resistant. These metabolites mostly act as deterrents or antifeedants, allelochemicals, toxins or precursors of other metabolites that defend plants from stresses. However, some pathogens use these metabolites as a signal for host recognition or nutrition rather than using them as toxins or deterrents. The SMs activate different signalling pathways e.g. terpenoids modulate the calcineurin pathway, sesquiterpenoids modulate the jasmonic acid and salicylic acid pathway, polyphenols activate the jasmonic acid and phenylpropanoid pathway, and alkaloids activate the salicylic acid pathway to protect against pathogens and herbivores. Polyphenolic compounds provide resistance to different microbes by expressing different pathogenesis-proteins and hypersensitive reaction-mediated cell death and eliminate pathogens by altering the membrane permeability (inhibiting efflux pump), cell wall integrity, suppressing enzyme activity, free radicals’ generation, inhibiting protein biosynthesis, damaging DNA and reducing the expression of virulent genes. Flavonoids help plants sustain pathogen stresses through the changes in the auxin transport process. The pathogen exposure upregulate genes of alkaloid synthesis pathways such as tyrosine decarboxylase (TyDC), S-norcoclurine synthase (NCS), codeinone reductase 2-like (COR-2), and StWRKY8 transcription factors which in turn accumulate alkaloids in large amounts. Plant exposure to pathogens leads to hypersensitivity reactions and phytoalexin accumulation. The plant's treatment of salicylic acid and jasmonic acid upregulated downstream transcription factors, increased the expression of defence proteins, triggered the synthesis of SMs, and provided resistance against multiple pathogens. Pathogens and herbivores have also coevolved to cope with defence metabolites by detoxifying the toxic metabolites, converting toxins into useful products, evolving their food choice, fast digestive system, expulsion of toxins, and down-regulation of the gene-producing secondary metabolites. This review article gives a molecular insight into the genes and regulatory proteins controlling the synthesis of SMs, which may help decipher the role of the biosynthetic pathway intermediates and thereby scoring genes providing resistance to various stresses. The article comprehensively describes the roles of different SMs in plant defence and their molecular mechanisms of action. © The Author(s), under exclusive licence to Springer Nature B.V. 2024.