Newly discovered ergot alkaloids in Sorghum ergot Claviceps africana occurring for the first time in Israel. Shimshoni JA(1), Cuneah O(2). Aust Vet J. Feb;78(2) Sorghum ergot (Claviceps africana) associated with agalactia and feed refusal in pigs and dairy cattle. Blaney BJ(1). PDF | On Jan 1, , S. Bhuiyan and others published Control of ergot ( Claviceps africana) on sorghum seed with fungicides.
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Metabolic pathway of oligosaccharides in sorghum honeydew caused by Claviceps africana. The occurrence of the alditol oligosaccharides in the Claviceps afriana honeydew is partly as a rational expression of the pathogen’s selective nutritive metabolism of the sucrose supplied by the host plant.
The experiments were carried out in laboratory and when 14 C-D-sucrose, 14 C-D-fructose or 14 C-D-mannitol radiolabelled saccharides were incorporated into: Glucose was used by the pathogen as nutritional source.
Part of the unused fructose moiety was reduced to mannitol by the pathogen’s enzymes which was also excreted into honeydew where reductase activity accepted 14 C mannitol. The mannitol was afdicana with fructose in a 2-position synthesizing the disaccharide 1- b -D-fructofuranosyl-D-mannitol and then the process was repeated by the mannitol moiety of the disaccharide to yield the trisaccharide 1,6-di- b -D-fructofuranosyl-D-mannitol, which became dominant.
The direct formation of alditol saccharides from monosaccharides in this way seems to be unique to C. The sugar composition of the honeydew exudate from ergot fungi parasiting grasses and cereals hosts has, until recently, been largely of academic interest, concerning only the resumed bland mixture of oligossacharides arising from the pathogen’s preferred use of the glucose component of the host’s sucrose MOWER et al.
In most species of ergot, several sugars are formed in the honeydew, and the resulting higher osmotic concentration in the floral cavity serves to draw in host fluids. Epidemiologically, the honeydew sugars have a function in the preservation of the conidia during dry periods and support the secondary sporulation for dispersal of conidia to other flowers. Recent spread of the pathogen around the world has focused attention on macrospores germination which is the most important factor in creating epidemics of ergot disease.
Experiments using 14 C with species of fungi known to contain large amounts of mannitol have generally shown that the hexitol is a primary product of heterotrophic assimilation LEWIS, However, no consideration has previously been given to the possibility that the intermediate metabolism of certain acyclic polyols could lead to significant changes in the molecular distribution of radioactivity in related sugars.
Thus, it appears that honeydew synthesis depends on the activities of fungal enzymes, and evidence is reported here supporting the idea of a mechanism of honeydew formation.
Whereby sucrose is drown from the host by conversion to new sugars in the diseased floral cavity. Male-sterile sorghum Sorghum bicolor L. Florets were aafricana with Claviiceps. New parasitic tissues exuded honeydew weeks after floret inoculation. From these plants, fresh mycelial tissue of Sphacelia sorghi anamorphic form of C. To each treatment aricana m Ci of 14 C-sucrose, 14 C fructose or 14 C mannitol was added.
The tubes were placed in a shaker and 50 m L samples were collected at intervals of 0; 0. The experiments were made with 4 replicates in each treatment. Experiments with radiolabeled substrates were carried out also with C. In other experiment, two potted sorghum plants with honeydew symptoms were collected from africanx tunnel and m L of water containing 4 m Ci of 14 C-sucrose were injected with micro syringe in the last internode. The honeydew produced at intervals of 20h and 40h in the laboratory was collected and evaluated.
Descending paper chromatography [Whatman 3MM No.
Claviceps africana (ergot)
The oligosaccharides separated in the chromatograms were eluted through a 2. The fractions collected were freeze-dried prior to saccharide analysis and bioassay. The dried chromatograms papers were exposed to Kodirex No-screen X-ray film for 3 days.
The autoradiographs clavideps were used to determine the radioactive areas, which were removed, cut in small pieces and centrifuged in eppendorff’s vessels.
The volume was dried down to at least 1mL and added in liquid scintillate.
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The radioactivity in the samples was determined by a Packard counter model The system was combined by two phases. A phase coaviceps a Fisons quadrupole mass spectrometer system in electron impact mode, and B a VG autospek Q system in chemical ionisation with negative ion mode to show molecular ions of derivatised monosaccharides.
The 14 C-labelled honeydew from the potted plants was analysed by quantification of the percentage of free Africaan and total D-fructose after hydrolysis in 1M of TFA. Total D-fructose represented a combination of free D-fructose, the D-fructose in sucrose and D-fructose in oligosaccharides. The glucose and fructose quantification was made by reading the absorbance in four different dilutions with three replicates each and related to a standard curve of D-glucose and D-fructose.
The optical clavicepa of each solution was measured against the blank reagents incubated with water at nm wavelength using a spectrophotometer MSE Spectroplus.
Standard glucose and fructose solutions m g mL -1prepared in saturated benzoic acid and diluted with water, were treated similarly and gave linear calibration curve and analysis of variance ANOVA was used for statistical analysis.
Concentration of each sample was expressed as g mL -1 using the D-fructose standard curve. During the experiment there was an increase in the amount of fructose until the total hydrolysis of sucrose. The cell free honeydew treated with 14 C-sucrose Figure 2 or 14 C-mannitol showed significant incorporation of radiolabell from both into 1- b -D-fructofuranosyl-D-mannitol and 1,6-di- b -D-fructofuranosyl-D-mannitol in the first hours.
When 14 C-fructose was added to the cell-free honeydew, even after 4 hours, no incorporation of radiolabell was observed. When Sphacelia’s tissue was macerated, the incorporation of 14 C-sucrose, 14 C-mannitol and 14 C-fructose into 1- b -D-fructofuranosyl-D-mannitol and 1,6-di- b -D-fructofuranosyl-D-mannitol was in general slightly more efficient compared to the whole Sphacelia’s tissue.
Particularly, the incorporation of 14 C-mannitol into the oligosaccharides with macerated Sphacelia’s clavviceps was approximately 1. When 14 C-sucrose, 14 C-mannitol or 14 C-fructose were added to cell-free-honeydew of C.
The distribution of various sugars in C. The majority of the total fructose is distributed in 1- b -D-fructofuranosyl-D-mannitol During the processes of sucrose catabolism and transformation by the enzymes of the sphacelial mass of C. The fructose moiety of sucrose, which initially is not used as nutrition source, is reduced to mannitol by fructose dehydrogenase and subsequently creating a serious of afrcana containing alditol. The alditol mannitol arises by reduction of fructose in afriacna sphacelial tissue and the formation of oligosaccharides is achieved as cell-associated metabolism.
By GC-MS linkage analysis, mannitol is linked in a 2-position of fructose creating the disaccharide 1- b -D-fructofuranosyl-D-mannitol. Similar linkage occurs with glucose moiety in the sucrose substrate which occurs without the fructose moiety ever being free.
When the biotransformation occurs in the cell-associated, glucose is liberated for direct utilisation by the pathogen’s metabolism but if the biotransformation occurs within exuded honeydew, free glucose is utilised for spores metabolism, including secondary sporulation.
The mannitol in the disaccharide 1- b -D-fructofuranosyl-D-mannitol is randomly linked or to fructose and addition of an extra fructose, also linked by its 2-position to the remaining 1- or 6- positions of mannitol in the disaccharide, gives the trisaccharide 1,6-di- b -D-fructofuranosyl-D-mannitol.
As in the formation of the disaccharide, mannitol becomes linked to an eventual 2-position of aricana fructose in another sucrose molecule, with concomitant release of glucose, but in this case the mannitol is already linked to a fructose moiety and creates a trisaccharide. Normally, the developing sphacelium of C.
This is why the concentration of saccharides in the honeydew is generally so low. The glucose moiety of sucrose is metabolised by the pathogen as a carbon and energy clabiceps, and the fructose moiety, partially reduced to mannitol, is incorporated into oligosaccharides.
The biosynthetic mechanism of linking mannitol to fructose molecules and the enzyme activity explain the increase in the concentration of bioactive oligosaccharides in honeydew. Glucose and fructose in the blood of the fetal sheep. Biochemical JournalLondon, v.
Biochemical physiopathology of some ergot fungi and other honeydew-producing plant parasites. The structures of the honeydew oligosaccharides synthesized by Claviceps africana.
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