RESUMO
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 14C-D-sucrose, 14C-D-fructose or 14C-D-mannitol radiolabelled saccharides were incorporated into: a) sorghum plant infected by C. africana, b) whole and macereted micelia tissue and c) cell-free honeydew of C. africana, it was observed that the glucose moiety of sucrose was not involved in oligosaccharides formation. 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 14C mannitol. The mannitol was linked with fructose in a 2-position synthesizing the disaccharide 1-beta-D-fructofuranosyl-D-mannitol and then the process was repeated by the mannitol moiety of the disaccharide to yield the trisaccharide 1,6-di-beta-D-fructofuranosyl-D-mannitol, which became dominant. The direct formation of alditol saccharides from monosaccharides in this way seems to be unique to C. africana, contrasting with the fructosyl transfer from sucrose to sucrose which is usual in others ergot parasites.(AU)
A ocorrência de oligossacarídeos contendo alditol em exsudações da doença açucarada produzidos por Claviceps africana é em parte uma expressão racional do metabolismo seletivo de nutrição do patógeno na tansformação da sacarose fornecida pela planta. Quando açúcares radioativos marcados com 14C (D-sucrose, D-fructose e D-mannitol) foram incorporados em: a) planta do sorgo infectada por C. africana, b) tecido micelial inteiro e macerado isolado de C. africana e c) exsudato livre de células de C. africana, foi observado que a glicose da sacarose não estava envolvida na formação de oligossacarídeos, sendo usada pelo patógeno como fonte nutritiva. Parte da frutose não utilizada da sacarose foi reduzida a mannitol por enzimas do patógeno. As enzimas envolvidas também atuaram no exsudato da "doença açucarada", ativando a ação da redutase pela incorporação do 14C manitol. O manitol foi ligado na posição 2 da fructose, formando o dissacarídeo 1-beta-D-fructofuranosyl-D-mannitol e, posteriormente, adicionada mais uma fructose ao mannitol do dissacarídeo, formando o trisacarídeo 1,6-di-beta-D-fructofuranosyl-D-manitol, que se tornou predominate. A formação direta de oligossacarídeos contendo alditol a partir de monossacarídeos parece ser exclusiva em C. africana, contrastando com a ação enzimática da frutose transferase a partir de sucrose para sucrose, a qual é muito comum em outros patógenos tipo "ergot".(AU)
Assuntos
Sorghum , ClavicepsRESUMO
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 14C-D-sucrose, 14C-D-fructose or 14C-D-mannitol radiolabelled saccharides were incorporated into: a) sorghum plant infected by C. africana, b) whole and macereted micelia tissue and c) cell-free honeydew of C. africana, it was observed that the glucose moiety of sucrose was not involved in oligosaccharides formation. 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 14C mannitol. The mannitol was linked with fructose in a 2-position synthesizing the disaccharide 1-beta-D-fructofuranosyl-D-mannitol and then the process was repeated by the mannitol moiety of the disaccharide to yield the trisaccharide 1,6-di-beta-D-fructofuranosyl-D-mannitol, which became dominant. The direct formation of alditol saccharides from monosaccharides in this way seems to be unique to C. africana, contrasting with the fructosyl transfer from sucrose to sucrose which is usual in others ergot parasites.
A ocorrência de oligossacarídeos contendo alditol em exsudações da doença açucarada produzidos por Claviceps africana é em parte uma expressão racional do metabolismo seletivo de nutrição do patógeno na tansformação da sacarose fornecida pela planta. Quando açúcares radioativos marcados com 14C (D-sucrose, D-fructose e D-mannitol) foram incorporados em: a) planta do sorgo infectada por C. africana, b) tecido micelial inteiro e macerado isolado de C. africana e c) exsudato livre de células de C. africana, foi observado que a glicose da sacarose não estava envolvida na formação de oligossacarídeos, sendo usada pelo patógeno como fonte nutritiva. Parte da frutose não utilizada da sacarose foi reduzida a mannitol por enzimas do patógeno. As enzimas envolvidas também atuaram no exsudato da "doença açucarada", ativando a ação da redutase pela incorporação do 14C manitol. O manitol foi ligado na posição 2 da fructose, formando o dissacarídeo 1-beta-D-fructofuranosyl-D-mannitol e, posteriormente, adicionada mais uma fructose ao mannitol do dissacarídeo, formando o trisacarídeo 1,6-di-beta-D-fructofuranosyl-D-manitol, que se tornou predominate. A formação direta de oligossacarídeos contendo alditol a partir de monossacarídeos parece ser exclusiva em C. africana, contrastando com a ação enzimática da frutose transferase a partir de sucrose para sucrose, a qual é muito comum em outros patógenos tipo "ergot".
RESUMO
The biogenetic origin of the carbon atoms in the 2-azaanthraquinone scorpinone ( 1), produced by the rare fungus Amorosia littoralis isolated from marine sediment, was explored through isotopic enrichment studies utilizing [2- (13)C]-acetate and [1,2- (13)C]-acetate. The labeling results reveal a heptaketide precursor is involved in the biosynthesis of 1, as has been found for the structurally related naphthoquinone dihydrofusarubin. The previously identified naphthoquinone herbarin ( 2) was also isolated and appears to bear the same biogenetic relationship to 1 as the fusarubins do to the fungal 2-azaanthraquinone bostrycoidins.
Assuntos
Antraquinonas/síntese química , Ascomicetos/química , Compostos Aza/síntese química , Sedimentos Geológicos/microbiologia , Antraquinonas/química , Compostos Aza/química , Bahamas , Estrutura MolecularRESUMO
The new generic and species name Amorosia littoralis gen. sp. nov. is introduced for the conidial dematiaceous hyphomycete isolated from the littoral zone in The Bahamas and reported in 2001 to produce the novel aza-anthraquinone scorpinone, and also caffeine. No satisfactory generic placement was found at the time, but subsequent morphological and molecular investigations reveal that a new generic name is required. The new genus has some similarity to several fungi described in Trichocladium, but differs substantially from the type species of that genus in the form of the conidia and the lack of ornamentation. BLAST studies using the 18S and 28S rDNA gene sequences place the new genus in the Sporormiaceae. In addition to the morphological studies, an ultrastructural examination of the conspicuous porate septa of hyphae showed that they do not belong to a basidiomycete.