Sekhar Shailasree

Involvement of mitogen-activated protein kinase signalling in pearl millet–downy mildew interaction

Mitogen-activated protein kinase (MAPK) cascade-mediated signalling is essential in the establishment of resistance towards pathogens. The present study compared MAPK activities in a compatible and incompatible interaction between pearl millet [Pennisetum glaucum (L.) R. Br.] and downy mildew pathogen Sclerospora graminicola. Differential expression was observed with rapid and increased activation of MAPKs, PgMPK1 (48kDa) and PgMPK2 (44kDa), in the incompatible interaction; with a weak activity of only PgMPK1 in the compatible interaction. Immunoblot analysis showed PgMPK1 and PgMPK2 to be orthologs of salicylic acid-induced protein kinase and wound-induced protein kinase, respectively. Immunocytochemical analysis revealed pathogen-induced accumulation and nuclear localisation of PgMPKs only in the incompatible interaction with highest signals in the vascular tissues. Maximum PgMPKs activation correlated with the activation of several defence-related enzymes. In addition, inhibition of MAPK-activation by kinase cascade inhibitors correlated with the suppression of defence-related enzyme activities and pathogen-induced H2O2 accumulation. Treatment of pearl millet seedlings with abiotic and biotic elicitors led to a strong early induction of only PgMPK1. β-Amino butyric acid and H2O2 were found to be best activators of PgMPK1. These results suggest that in pearl millet MAPK signalling is involved in mediating several defence mechanisms in response to pathogen infection.

Curative properties of Buchanania lanzan: As evaluated by its anti-oxidant, anti-inflammatory and DNA protective properties

Parts of B. lanzan is reported to have several medicinal properties. Methods: Buchanania lanzan bark was assessed for its anti-oxidant, anti-inflammatory, and DNA protective properties. Results: Soxhlet solvent extracts exhibited DPPH scavenging capacity to a varied extent. Methanolic extract could scavenge ABTS radicals with IC50 of 0.25 mg/ml. The anti-inflammatory properties were elucidated by its capacity to inhibit 15-lipoxygenase and human cyclooxygenase-2. As a measure of anti-ageing effect, anti-hyaluronidase and anti-elastase activity was measured. The extract significantly inhibited both 15- LOX and human COX-2 in a dose-dependent manner. The extract abolished elastase activity and inhibited hyaluronidase as observed in zymogram by substrate-gel assay. In addition, the methanolic extract could prevent damage to DNA from the hydroxyl radicals produced during Fenton reaction. Further, an absence of hemolytic activity for this extract suggests the non-toxic nature. Conclusion: Studies on unexplored medicinal plants may lead to identification of potential drug candidates

b-Amino Butyric Acid â Resistance Inducing Agent in Pearl Millet

β-amino butyric acid (BABA), applied as inducer of resistance to the seeds of susceptible cultivar of pearl millet [Pennisetum glaucum (L) R Br] against downy mildew [Sclerospora graminicola (Sacc) Schroet]. Infection offered protection to the host operative through vegetative and reproductive growth. Biochemical studies identified a close association between BABA-treatment and accumulation of defence-related proteins like phenylalanine ammonia lyase, peroxidise and β-1,3-glucanase. Studies on phenotypic host defence identified modifications in host cell wall leading to papillae formation with hydroxyproline-rich glycoproteins (HRGPs) as its major constituent. The HRGPs were identified as extensions by use of MAC 265 monoclonal antibodies. PgMPK4 (mitogen-activated protein kinase) was identified as the crucial signal transduction module signalling of pathogen cues. This increased accumulation of PgMPK4 mRNA and kinase activity in BABA-treated samples and further kinase inhibitor treatments providing critical evidence of PgMPK4 involvement in the JA- and SA mediated expression of defence genes, it may be assumed that BABA-induced resistance could be a JA/SA mediated phenomenon.

Serodiagnosis of pearl millet resistance to downy mildew by quantitating cell wall P/HRGP using polyclonal antiserum Pab-P/HRGP

Proline/hydroxyproline-rich glycoprotein (P/HRGP) level in pearl millet genotypes resistant to downy mildew increase after inoculation with the oomycete pathogen Sclerospora graminicola. Using purified P/HRGPs from pearl millet cell walls, polyclonal antibodies (Pab-P/HRGP) were raised in rabbit. Based on this antiserum, an enzyme immunoassay was developed that displays a linearity detection range from 0.01 to 10 μg P/HRGP. Western blot analysis, confirming the induction of three marker P/HRGPs in the infected resistant genotype, and immunocytochemical studies on P/HRGP localization either in epidermal peelings or in suspension-cultured cells demonstrated the specificity of the antiserum. Besides its characterization, Pab-P/HRGP was employed to screen various genotypes of pearl millet for fast, sensitive and specific detection of induced P/HRGPs upon infections. The results presented are discussed with presumed importance to downy mildew disease and the use of this new antiserum in pearl millet screening for disease resistance.

Bioactive Potential of Medicinal Plants from Western Ghats Region, India

Methanol extracts of Elaeocarpus, E. serratus, E. tuberculatus (Elaeocarpaceae), Catunaregam uliginosa, C. spinosa (Rubiaceae), Elaeagnus conferta (Elaeagnaceae), Evodia lunu-ankenda (Rutaceae), Glycosmis arborea (Rutaceae), Melastoma malabathricum. (Melastomataceae), and Smilax zeylanica (Liliaceae) leaves were screened for antioxidant, anti-inflammatory, and cytotoxicity to Vero cell lines. 1,1-diphenyl-2-picrylhydrazyl and 2-2′-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid radical scavenging capacities were identified C. spinosa and E. tuberculatus. Anti-inflammatory capacity with lipoxygenase and human cyclooxygenase-2 inhibition for E. tuberculatus and E. serratus was recorded. The extracts prevented DNA damage by hydroxyl radicals produced by Fenton reagent. Cell cytotoxicity studies revealed S. zeylanica and E. tuberculatus with potent cytotoxicity to Vero cells.

Identification and characterization of Memecylon species using isozyme profiling

Background: The protein/isozyme fingerprint is useful in differentiating the species and acts as a biochemical marker for identification and systematic studies of medicinal plant species. Objective: In the present study, protein and isozyme profiles for peroxidase, esterase, acid phosphatase, polyphenol oxidase, alcohol dehydrogenase, and alkaline phosphatase of five species of Memecylon (Melastomataceae), Memecylon umbellatum, Memecylon edule, Memecylon talbotianum, Memecylon malabaricum, and Memecylon wightii were investigated. Materials and Methods: Fresh leaves were used to prepare crude enzyme extract for analyzing the five enzymes isozyme variations. Separation of isozymes was carried out using polyacrylamide gel electrophoresis (PAGE) and the banding patterns of protein were scored. Pair-wise comparisons of genotypes, based on the presence or absence of unique and shared polymorphic products, were used to regenerate similarity coefficients. The similarity coefficients were then used to construct dendrograms, using the unweighted pair group method with arithmetic averages. Results: A total of 50 bands with various Rf values and molecular weight were obtained through PAGE analysis. Among the five Memecylon species, more number of bands was produced in M. wightii and less number of bands was observed in M. edule. The results of similarity indices grouped M. malabaricum and M. wightii in one cluster with 98% similarity and M. umbellatum, M. edule, and M. talbotianum are grouped in another cluster with 79% similarity showing close genetic similarities which is in accordance with the morphological identification of Memecylon species. Conclusion: The protein/isozyme fingerprint is useful in differentiating the species and acts as a biochemical marker for identification of Memecylon species. Abbreviations Used: SDS-PAGE: Sodium docecyl sulfate polyacrylamide gel electrophoresis; NTSYS PC2: Numerical taxonomy system, version 2.2 for Windows XP, Vista, Win7, Win 8 and Win10 including 64 bit