Analysis of a Secreted Aspartic Peptidase Disruption Mutant of Glomerella cingulata

Peptidases have been implicated in the pathogenicity of fungi that cause disease in plants. Expression of the secreted aspartic peptidase gene (gcsap), of a Glomerella cingulata isolate pathogenic on apples, is induced during appressorium formation. To determine whether the secreted aspartic peptidase (GcSAP) is essential to pathogenicity, gcsap was disrupted using a vector containing a 637 bp fragment of genomic DNA that encodes the sequence spanning the two active site aspartic acid (Asp) residues. To ensure that the truncated gcsap gene products could not have residual peptidase activity the codons for the active site residues Asp¹¹² and Asp²⁹⁷ were both mutated to histidine residues. Both PCR and Southern analysis confirmed disruption of gcsap. Neither gcsap mRNA nor GcSAP activity was detected in the disruption mutant. Pathogenicity tests on fruit from three apple cultivars showed that GcSAP was not required for pathogenicity. The disruption mutant grew on medium containing protein as the sole source of nitrogen because G. cingulata secretes a previously undetected peptidase(s). A serine peptidase that had a pH optimum between pH 7.0 and 8.0 and a K _m of 0.25 mM for the synthetic substrate succinyl-Ala–Ala–Pro–Phe-p-nitroanilide was identified.     

PGPR and entomopathogenic fungus bioformulation for the synchronous management of leaffolder pest and sheath blight disease of rice

BACKGROUND: The biological control of plant pests and diseases using a single organism has been reported to give inconsistent and poor performance. To improve the efficacy, bioformulations were developed possessing mixtures of bioagents. RESULTS: Bioformulations combining Pseudomonas fluorescens Migula strains Pf1 and AH1 and Beauveria bassiana (Balsamo) Vuill. isolate B2 were developed and tested for their efficacy against leaffolder pest and sheath blight disease on rice under glasshouse and field conditions. The combination of Pf1, AH1 and B2 effectively reduced the incidence of leaffolder insect and sheath blight disease on rice compared with other treatments. An in vitro assay of leaffolder preference to rice leaf tissues treated with Pf1 + AH1 + B2 biformulation showed variation from normal growth and development of leaffolder larvae. Plants treated with the Pf1 + AH1 + B2 combination showed a greater accumulation of enzymes, lipoxygenase and chitinase activity against leaffolder insect compared with other treatments. Similarly, the plants showed a higher accumulation of defence enzymes, peroxidase and polyphenol oxidase activity against sheath blight pathogen in Pf1 + AH1 + B2 treatment compared with the untreated control. The bioformulation mixture attracted the natural enemy population of leaffolder under field conditions. In addition, a significant increase in rice grain yield was observed in Pf1 + AH1 + B2 treatment compared with the untreated control. CONCLUSION: The combination of P. fluorescens strains and B. bassiana isolate effectively reduced the incidence of leaffolder insect and sheath blight disease on rice plants and showed the possibility of controlling both pest and disease using a single bioformulation. Copyright © 2010 Society of Chemical Industry     

Genetics of growth habit in horse gram [Macrotyloma uniflorum (Lam.) Verdc.]

Genetic Resources and Crop Evolution - Growth habit is a plant architectural trait in grain legumes with no exception of horse gram [Macrotyloma uniflorum (Lam.) Verdc.]. Determinacy and...     

Comparative analysis of innate immune parameters of the skin mucous secretions from certain freshwater teleosts, inhabiting different ecological niches

The innate immune system of fish is considered first line of defense against a broad spectrum of pathogens. Being a component of innate immunity and lying at the interface between fish and the aqueous environment, skin mucus plays a frontier role in protecting fish from infections. In the present study, skin mucus of Cirrhinus mrigala, Labeo rohita, Catla catla, Rita rita and Channa punctata, inhabiting different ecological niches, was analyzed to characterize potential innate immune factors such as lysozyme, proteases, phosphatases, esterase and sialic acid. The enzyme activities were high in bottom dweller species, C. punctata and C. mrigala, and low in clean water inhabiting species, L. rohita and C. catla. An inverse relationship was observed between the level of enzyme activity and the sialic acid content in these fish species. In R. rita, however, the levels of all factors were found to be low. Zymographic analysis with labeled Micrococcus lysodeikticus revealed three isoforms of lysozyme in C. punctata and two in each species, C. mrigala, L. rohita and C. catla. In R. rita, lysozyme could not be detected. Gelatin zymography revealed that serine and metalloproteases were the major mucus proteases in all fish species investigated. In addition, trypsin-like protease and Ca(++)-specific serine proteases were observed in skin mucus. Increased knowledge of these parameters could be useful in understanding the role of skin mucus in the innate immune system of fish species inhabiting different ecological niches.     

Improved dispersion of carbon nanotubes in chitosan

Carbon nanotubes (CNT)/chitosan films and fibers can find use in specialized applications like the artificial muscles and other intelligent switching devices. The dispersion state of the single walled carbon nanotubes (SWCNTs) in chitosan matrix plays a major role in deciding the ultimate properties of composite. A suitable chemical treatment for purification and functionalization of SWCNTs is reported. Optimal conditions to prepare water soluble and stable, dispersion of SWCNT in chitosan are presented. The dispersion behavior of purified and functionalized SWCNT was characterized by visual observations, transmission electron microscopy (TEM), and Raman spectroscopy. The dispersion obtained using functionalized SWCNT was stable, while the purified SWCNT dispersion showed limited stability. The better stability of functionalized SWCNT dispersion in chitosan was evidenced by improved interaction between chitosan and carboxyl functional groups of SWCNT.     

Efficacy and effects of clove oil and MS‐222 on the immune‐biochemical responses of juvenile rohu Labeo rohita

The present study determined the effective concentrations of clove oil and MS‐222 in juvenile rohu Labeo rohita for quick induction and recovery. The immune‐biochemical responses due to 0, 1 and 24 hr exposure to those anaesthetics were also evaluated. Of four concentrations of the anaesthetics examined, the lowest effective concentration of clove oil and MS‐222 were 50 µl/L and 125 mg/L respectively. Clove oil and MS‐222 significantly increased the myeloperoxidase, total protein and alkaline phosphatase activity at some of the holding durations. However, superoxide anion production (after 0 and 1 hr) and antiprotease activity (after 24 hr) were significantly reduced in fish exposed to clove oil. Serum glucose content was significantly elevated in the MS‐222‐treated group. Furthermore, the clove oil‐treated group showed significantly higher levels of serum Na⁺ and K⁺, while the aspartate and alanine aminotransferase activities were significantly enhanced in the MS‐222 group. The use of both clove oil and MS‐222 is advised as an anaesthetic agent for rohu with a bias towards clove oil, considering its economic and operational feasibility.     

Competitiveness of native Bradyrhizobium japonicum strains in two different soil types

Interstrain competitiveness is a key factor affecting the performance of rhizobium inoculant. In the present study five native strains of Bradyrhizobium japonicum, namely SSF 4, SSF 5, SSF 6, SSF 7 and SSF 8, were assessed for their competitiveness in nodulating soybean using serological methods. The strains were inoculated individually or with the type strain USDA 110 at a 1:1 ratio. Nodule occupancy determined by immunofluorescence and dot immunoblot assay revealed that under in vitro conditions SSF 8 is more competitive than USDA 110 whereas the others were less competitive. The competitive ability of these strains was also estimated in pot culture in the field. In red soil both SSF 8 and USDA 110 were equally competitive whereas in black soil SSF 8 competed better than USDA 110 and produced more nodules. In a black soil field trial using a randomized block design, USDA 110 or SSF 8, when inoculated alone, occupied the majority of the nodules and enhanced nodule dry weight and shoot biomass. SSF 8 was more competitive when the strains were co-inoculated. Received: 1 November 1996     

Total and soluble fluorine concentrations in relation to properties of soils in New Zealand

Soil fluorine (F) concentrations continue to increase in agricultural soils receiving regular applications of phosphatic fertilizer. Continued accumulation of soil F poses a risk to grazing ruminants and may pose a future risk to groundwater quality. This paper examines the range of total F (F_t) concentrations and forms of soluble F species and their relationship to selected soil properties in New Zealand agricultural soils. The F_t and soluble F (soil F extracted with water (F_water) and 0.01 m KCl (F_KCl)) concentrations in 27 soil samples (0–75 mm depth) taken from predominantly pasture sites in the North and South Islands of New Zealand were much less than those reported in the literature for sites contaminated with F from industry. The F_t concentrations ranged from 212 to 617 µg F g^?1 soil. The F‐toxicity risk to grazing animals in farms at these sites through soil ingestion is small at present, but farms with very large F_t concentrations (i.e. > 500 µg F g^?1) need to adopt suitable grazing and fertilizer management practices to avoid future F‐toxicity risk. The F_t concentration had very strong positive correlations with both total soil P and total soil Cd concentrations, reflecting the link between P fertilizer use and F accumulation in the soils. It also had significant positive correlations with organic matter and amorphous Al oxides contents, indicating that F is strongly bound to Al polymers adsorbed to organic matter and amorphous Al oxides. The F_water and F_KCl concentrations and free F^– ion concentrations in water (F^–_water) and 0.01 m KCl (F^–_KCl) extracts were generally two and three orders of magnitude, respectively, less than the F_t concentrations and were much less than the concentrations considered phytotoxic. The F_water and F_KCl concentrations were positively related to soil organic matter content and negatively related to soil pH. Regression models relating F_water and F_KCl concentrations to soil organic matter content and soil pH suggest that F can be very soluble in extremely acidic soils (pH(water) < 4.9) with large organic matter contents and therefore F potentially may contaminate groundwater if these soils are also coarse‐textured and the water table is shallow.     

Radiation-induced enhancement of antioxidant contents of soybean (Glycine max Merrill)

Soybean samples were treated with gamma-radiation doses between 0.5 and 5 kGy for achieving insect disinfestation and microbial decontamination. Nutritional quality of soybeans with respect to antioxidant isoflavone content was tested in radiation-treated and untreated samples. Changes in major isoflavones such as genistein, diadzein, glycetein, and their glycosides were monitored by high-performance liquid chromatography. Interestingly, a decrease in content of glycosidic conjugates and an increase in aglycons were noted with increasing radiation dose. Antioxidant potential measured as percent 1,1-diphenyl-2-picrylhydrazyl scavenging activity showed an increasing trend with dose, indicating that radiation processing as a method of food preservation has a positive nutritional implication.