Swarnendu Chandra

Chitosan nanoparticles: A positive modulator of innate immune responses in plants.

The immunomodulatory role of the natural biopolymer, chitosan, has already been demonstrated in plants, whilst its nanoparticles have only been examined for biomedical applications. In our present study, we have investigated the possible ability and mechanism of chitosan nanoparticles (CNP) to induce and augment immune responses in plants. CNP-treatment of leaves produced significant improvement in the plant’s innate immune response through induction of defense enzyme activity, upregulation of defense related genes including that of several antioxidant enzymes as well as elevation of the levels of total phenolics. It is also possible that the extracellular localization of CNP may also play a role in the observed upregulation of defense response in plants. Nitric oxide (NO), an important signaling molecule in plant defense, was also observed to increase following CNP treatment. However, such CNP-mediated immuno-stimulation was significantly mitigated when NO production was inhibited, indicating a possible role of NO in such immune induction. Taken together, our results suggest that CNP may be used as a more effective phytosanitary or disease control agent compared to natural chitosan for sustainable organic cultivation.

Apoptogenic effects of Tricholoma giganteum on Ehrlich's ascites carcinoma cell

This study explored the efficacy of Fa fraction of Tricholoma giganteum against Ehrlich’s ascites carcinoma (EAC). Mechanisms of apoptogenic effect of the fraction were delineated. The flow cytometric analysis of EAC cells, showed an increase in number of cells in sub-G0/G1 population and reduction in the G2/M phase due to the treatment thus suggesting apoptosis. The induction of apoptosis has also been confirmed by nuclear staining that demonstrated distinctive morphological features of apoptosis. Our data also revealed an increase in the expression of pro-apoptotic protein p53 in EAC and induced factors contributing to apoptosis. Pro-apoptotic gene Bax was up-regulated during p53-mediated apoptosis. No significant change in the expression of anti-apoptotic protein Bcl-2 was observed ensuing in decrease of the Bcl-2/Bax ratio. p53-mediated growth arrest involves p21 as a major effecter, which interestingly showed moderate elevation. All these observations indicate that Fa fraction of T. giganteum induces apoptogenic signal in EAC.

Nitric oxide functions as a signal in induced systemic resistance

The study was aimed to search out the probable molecule behind the activation of a broad spectrum resistance during Pseudomonas aeruginosa WS-1 mediated induced systemic resistance (ISR) in Capsicum annuum where plants were challenged inoculated with its pathogen Colletotrichum capsici 24 h after induction of ISR. On the fourth day after pathogen inoculation a significant increase of pathogenesis-related (PR) proteins, other defence enzymes and phenolics as well as a two-fold increase of nitric oxide (NO) a potent defence signalling molecule were observed. Treatment of the host with NO donor also induced the same defence molecule in a similar manner. Results suggest the possible signalling role of NO in ISR during crosstalk between ISR inducing agent and pathogen within the host system.

Sublethal Heavy Metal Stress Stimulates Innate Immunity in Tomato

Effect of sublethal heavy metal stress as plant biotic elicitor for triggering innate immunity in tomato plant was investigated. Copper in in vivo condition induced accumulation of defense enzymes like peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL), and β-1,3 glucanase along with higher accumulation of total phenol, antioxidative enzymes (catalase and ascorbate peroxidase), and total chlorophyll content. Furthermore, the treatment also induced nitric oxide (NO) production which was confirmed by realtime visualization of NO burst using a fluorescent probe 4,5-diaminofluorescein diacetate (DAF-2DA) and spectrophotometric analysis. The result suggested that the sublethal dose of heavy metal can induce an array of plant defense responses that lead to the improvement of innate immunity in plants.

Boosting of Innate Immunity in Chilli

Chilli (Capsicum annuum L.), an economically important crop, suffers from many field and post harvest diseases. Traditional pesticide control is hazardous to the environment, giving rise to the search for alternatives. Our objective was to increase the innate defense molecules in chilli by an abiotic (calcium chloride) and biotic (chitosan) elicitors. Foliar applications of elicitors increased β-1, 3 glucanase, peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, catalase and phenolics. Treatment with elicitors elicited production of nitric oxide, an important signalling molecule in plant defense. A single application of a nitric oxide donor increased all molecules of innate immunity supporting the role of nitric oxide as the signalling molecule for elicitor mediated increase of innate immunity.

In Vitro Protective Ability of Ramaria aurea Against Free Radical and Identification of Main Phenolic Acids by HPLC

Free radical scavenging activity of Ramaria aurea, an edible mushroom, naturally grown in Shilong, India, was evaluated. A heat-stable, polyphenol-rich extract (RauPre) was prepared from the dried basidiocarps and analyzed. The major chemical constituent of RauPre was phenols (26.86 μg gallic acid equivalents [GAE] mg−1 of dry extract); flavonoids, β-carotene, lycopene, and ascorbic acid were present in minor amounts. Main phenolic acids identified by high performance liquid chromatography (HPLC) were caffeic acid > cinnamic acid > gallic acid. Results from antioxidant assays demonstrated potential for superoxide and DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity (EC50 0.283 mg mL−1 and 0.384 mg mL−1, respectively). RauPre chelated ferrous ion (EC50 0.95 mg mL−1) and had Fe3+ to Fe2+ reducing power (EC50 1.025 mg mL−1). The activity of 1 mg of RauPre was equivalent to 86.7 μg ascorbic acid for total antioxidant capacity.

Introducing a novel mushroom from mycophagy community with emphasis on biomedical potency

Mushrooms have been prized by humankind as medicine and culinary wonder since antiquity. Though several species are ethnically valued; many prospective species are still being discovered. One such wild macrofungus has recently been discovered during subsequent field surveys in West Bengal, India which in turn exposed as a traditionally consumed popular myco-food. The collected taxon was found to be unique with regard to its morphological as well as genetical features. After detailed characterizations, the fungus was identified as a novel taxon belonging to the genus Russula (Russulaceae, Basidiomycota). Besides, the investigation was further extended in search of new functional ingredients and in this context, a water soluble crude polysaccharide rich extract (Rusalan) was isolated from dried basidiocarps. Accumulating evidences from GC-MS, HPTLC, FT-IR along with several spectrophotometric methods postulated that the fraction consisted mainly of carbohydrate in triple helical conformation, where glucose was the major monosaccharide mostly with β-type glycosidic linkage. Conversely, Rusalan showed pronounced antioxidant activity in six in vitro assay systems with EC50 value ranging from 190–1328 μg/ml concentration. The crude polysaccharide was also evaluated against six bacterial strains using microdilution method and the growth of Staphylococcus aureus and Bacillus subtilis were found to be inhibited effectively. In addition, immune-stimulatory assays demonstrated that Rusalan could evidently promote proliferation, induce phagocytosis, release NO, produce intracellular ROS and upregulate mRNA expression of iNOS, TNF-α, COX-2, as well as IL-6 genes in in mouse macrophage cells. Therefore, aim of the present study was not only to describe a new taxon to the world mycoflora but also to introduce a potent therapeutic agent that could be explored for food and pharmaceutical purposes. However, isolation of active component and in vivo studies need to be designed further.

In silico characterization, homology modeling of Camellia sinensis chitinase and its evolutionary analyses with other plant chitinases

Camelliasinensis (L.) Kuntze (commonly called tea plant) is an economically important cash crop in India. This plant is prone to infection by several fungal pathogens. Chitinases (EC 3.2.1.14) are enzymes that play a significant role in plants by hydrolyzing the N-acetylglucosamine polymer chitin. The present study entails different in silico characterization of chitinase enzyme using complete chitinase cDNA sequence from C. sinensis (CsChi). Template crystal structure of class I chitinase from Oryza sativa (PDB ID: 2DKV) was used for homology modeling of the CsChi enzyme. The model structure was refined and verified by using Structural Analysis and Verification Server (SAVES). The predicted model was submitted to the Protein Model Data Base (PMDB ID: PM0079561) and was docked with the chitin ligand, obtained from ChemSpider database. The results revealed that Serine in the predicted active site at position 199 of the enzyme is responsible for strong hydrogen bonding affinity with the ligand. Results of the evolutionary analysis showed that the obtained amino acid sequence of the CsChi enzyme belongs to class Ib chitinase.

Biochemical basis of improvement of defense in tomato plant against Fusarium wilt by CaCl2

The objective of this study was to investigate the effectiveness of calcium chloride (CaCl2), as potential elicitor, on tomato plants against Fusarium oxysporum f. sp. lycopersici. Foliar application of CaCl2 showed significant reduction of wilt incidence after challenge inoculation. Increased production of defense and antioxidant enzymes was observed in elicitor treated sets over control. Simultaneously, altered amount of phenolic acids were analyzed spectrophotometrically and by using high performance liquid chromatography. Significant induction of defense-related genes expressions was measured by semi-quantitative RT-PCR. Greater lignifications by microscopic analysis were also recorded in elicitor treated plants. Simultaneously, generation of nitric oxide (NO) in elicitor treated plants was confirmed by spectrophotometrically and microscopically by using membrane permeable fluorescent dye. Furthermore, plants treated with potential NO donor and NO modulators showed significant alteration of all those aforesaid defense molecules. Transcript analysis of nitrate reductase and calmodulin gene showed positive correlation with elicitor treatment. Furthermore, CaCl2 treatment showed greater seedling vigor index, mean trichome density etc. The result suggests that CaCl2 have tremendous potential to elicit defense responses as well as plant growth in co-relation with NO, which ultimately leads to resistance against the wilt pathogen.