Effect of alternaria pathotoxin(s) on expression of p53-like apoptotic protein in calli and leaves of Brassica campestris.

Possible involvement of apoptosis was investigated in pathotoxin-treated and nutritionally-depleted in vitro cultured calli by comparing levels of p53-like protein. Antibodies raised against human p53 were used to detect and quantify p53 in B. campestris. Expression of p53-like protein increased from proliferating to static growth stage and reached to constant level at decaying stage. Both ELISA and dot immuno-binding assay showed that p53-like protein was over expressed in toxin treated and nutritionally depleted calli. Almost similar changes were seen in senescent damage in Brassica species indicating involvement of p53 dependent pathways.

Generation of anti-teliospores antibodies for immunolocalization and characterization of antigenic epitopes of teliospores of Karnal bunt (Tilletia indica) of wheat.

Polyclonal antibodies raised against intact teliospores of T. indica in New Zealand albino rabbits were used for the development of indirect immunofluorescence tests. Specificity of anti-teliospore antibodies was evaluated by cross reactivity studies on other bunt, smut and related pathogens. The characteristic reactivity pattern indicated that the antibodies reacted with Tilletia species only. Chemical modifications, heat and enzyme treatments followed by indirect immunofluorescence tests were employed to delineate the molecular nature of the surface antigens. There was partial or no loss in immunoreactivity by methanol, periodate, heat or trypsin treatments. Extensive periodate treatment altered the fluorescence pattern due to changes in configuration of carbohydrate antigen present in episporium. Sequential treatment of periodate and trypsin showed diminished fluorescence due to access of proteolytic enzyme into inner site of episporium thereby cleaving peptide epitope(s) after reorientation of carbohydrate moietiesby periodate treatment. It indicated glycoprotein nature or peptide nature of epitopes on the teliospore surface.

Molecular signaling in pathogenicity and host recognition in smut fungi taking Karnal bunt as a model system.

Karnal bunt of wheat, incited by a phytopathogen Tilletia indica (Syn. Neovossia indica) is a floret infecting disease. In the floral tissues fungus proliferates and produces massive amount of black spores. In smut fungi, belonging to order Ustilaginales, communication between cells is necessary to regulate growth, differentiation and monokaryotic to dikaryotic transition during pathogenic and sexual development. Neighbouring cells are able to communicate with each other by direct cell to cell contact through plasma membrane bound signaling molecules or through formation of gap junctions and alternatively through secretion of chemical signals if cells are some distance away. Current research efforts toward understanding of pathogenic and sexual development in phytopathogenic fungi, offer a number of opportunities. These include the analysis of molecular signal(s) for direct contribution of sexual interactions to ability of smut and bunt pathogens to cause disease. These efforts will provide not only to explore the mechanisms of pathogenesis, but also to enhance knowledge of basic cellular biology of an economically important group of fungi.

Modulation of antigenicity of mycelial antigens during developmental cycle of Karnal bunt (Tilletia indica) of wheat.

Indirect enzyme linked immunosorbent assays (ELISA) were developed using polyclonal antibodies against soluble cytoplasmic (SCA) and insoluble cell wall antigens (ICWA) for monitoring modulation of mycelial antigens during growth cycle of T. indica. With SCA, continuous decrease in ELISA reactivity was observed in maturing fungus cultures, suggesting that SCA were expressed predominantly during early vegetative phase and their decreasing role was apparent as the fungus matures possibly towards sporogenous mycelium. In case of ICWA, the reaction profile showed an increase up to exponential phase of growth probably due to increase in the cell division and branching of mycelium. But later, ICWA antibody reactivity was decreased which may be due to conversion of mycelial phase to sporogenous phase, a quiescent stage of growth. Characterization of changes in antigenic configuration during developmental cycle of Tilletia indica by these antibodies could prove to be useful in identification of developmentally related and virulence marker(s).

Isolation of Gln- mutants through transposon, Tn917, mutagenesis in Bacillus brevis.

Transposon, Tn917, carried on pTV1 plasmid has been used successfully to mutagenise Bacillus brevis. The transposon showed preference for insertion at an "aro" site. A second insertional event after elimination of the preferred site with ethidium bromide/acridine orange treatment has permitted isolation of Gln- mutants in B. brevis.

Modification of glutamine synthetase in Bacillus brevis AG 4.

The various forms of glutamine synthetase obtained from Bacillus brevis have been found to be antigenically identical. Alkaline phosphatase treatment of the fast moving form (GS4) reduced the electrophoretic mobility of the enzyme. Radiolabelling and autoradiographic studies have also indicated that 32P-incorporation is high in the form depicting high Rm value. Thus, it appears that these forms arise due to covalent modification of the enzyme involving a phosphate group.

Multiple forms of glutamine synthetase in Bacillus brevis AG 4.

Glutamine synthetase in Bacillus brevis AG 4, a Gram-positive spore forming bacteria, has been found to exist in multiple molecular forms. It was purified to electrophoretic homogeneity by single-step Blue Sepharose affinity chromatography. The native enzyme has a molecular weight of 600,000 with subunits of 50,000. The enzyme samples purified from different stages of growth differed in Mg2+ sensitivity and other kinetic properties. Four different enzyme samples selected on the basis of Mg2+ sensitivity showed distinct mobilities at pH 6.3 on PAGE using discontinuous buffer system. A correlation amongst Mg2+ sensitivity, electrophoretic mobility, and kinetic properties was highly suggestive of multiple forms of glutamine synthetase in Bacillus brevis arising due to modification.