ABSTRACT
In recent years, interest in the ability of non-pathogenic microorganisms to induce resistance in plants has grown, particularly with respect to their use as environmentally safe controllers of plant disease. In this study, we investigated the capacity of Mucor ramosissimus Samutsevitsch to release pectinases able to degrade cell walls of Palicourea marcgravii St. Hil., a tropical forest native Rubiaceae on which the spores of this saprobic fungus have been found. The fungus was grown in liquid culture medium containing pectin as the sole carbon source and filtrates were analyzed for pectinase activity. An endopolygalacturonase was partially purified by ion exchange chromatography, gel filtration, and preparative isoelectrofocusing, and characterized. This enzyme was more active upon pectic substrates with a low degree of methyl esterification. The products of hydrolysis of different pectic substrates (including pectin from P. marcgravii) by the action of this endopolygalacturonase elicited to different extents the phytoalexin production in soybean cotyledons. Also, the enzyme itself and the products of its action on the pectic fraction of P. marcgravii elicited the production of defensive compounds in the leaves of the plant. These results suggest that, besides the role in recycling organic matter, saprobes may also play an important role in the induction of defensive mechanisms in wild plants by enhancing their non-specific resistance against pathogens. Furthermore, they set the stage for future studies on the role of saprobic fungi in inducing resistance of host plants to pathogens.
Subject(s)
Mucor/enzymology , Plant Proteins/metabolism , Polygalacturonase/metabolism , Rubiaceae/microbiology , Biological Products/metabolism , Biological Products/pharmacology , Cell Wall/metabolism , Cladosporium/drug effects , Cotyledon/drug effects , Cotyledon/metabolism , Culture Media , Esterification , Hydrolysis , Mucor/growth & development , Pectins/metabolism , Plant Leaves/metabolism , Plant Proteins/isolation & purification , Polygalacturonase/isolation & purification , Sesquiterpenes , Glycine max/drug effects , Glycine max/metabolism , Substrate Specificity , Terpenes/metabolism , PhytoalexinsABSTRACT
A vegetação herbácea do cerrado brasileiro apresenta sistemas subterrâneos ricos em frutanos e estacionalmente expostos à restrição hídrica. A fim de avaliar o envolvimento dos frutanos na tolerância à dessecação foram conduzidos experimentos utilizando plantas intactas e fragmentos de rizóforos de Vernonia herbacea. O conteúdo de água nos rizóforos de plantas intactas foi mantido por 30 dias, quando as plantas foram molhadas a cada 7 ou 15 dias, sendo que as plantas permaneceram vivas até 60 dias sem água. O conteúdo total de frutanos, a razão oligo/polissacarídeos e a massa molecular média dos polissacarídeos nessas plantas aumentaram, indicando haver ocorrido despolimerização de moléculas com tamanho intermediário das cadeias. Nos fragmentos apicais de rizóforos submetidos à dessecação, os oligossacarídeos aumentaram em relação aos polissacarídeos, um dia após a excisão dos tecidos tratados. Essas alterações foram facilmente detectadas através dos perfis de oligossacarídeos analisados por HPLC, nos quais a proporção de frutose livre e de frutanos com GP 4 - 10 aumentou acentuadamente. Os resultados indicam que o metabolismo de frutanos está envolvido na tolerância à dessecação de Vernonia herbacea.
ABSTRACT
Estuda a situaçäo da pesquisa e capacitaçäo de recursos humanos na área da saúde, no Brasil. Analisa as seguintes áreas: médica, odontológica, enfermagem, educaçäo física e terapia ocupacional. (NMPM)
Subject(s)
Education, Graduate , Health Workforce , Brazil , Education, Dental , Education, Medical , Education, NursingABSTRACT
The involvement of active oxygen species and apoplastic peroxidases in the mechanism of phytoalexin induction were evaluated in soybean hypocotyls using an eliciting extract from the saprophytic fungus Mucor ramosissimus. Hydrogen peroxide and ferric chloride-ascorbic acid a .OH radical generating system, promoted glyceollin production and increase in peroxidase activity similar to those observed with the fungal elicitor. Addition of catalase or potassium ferrocyanide (an inhibitor of peroxidase) inhibited both processes. It is suggested that there is a cause-effect relationship between peroxidase activity and phytoalexin induction both triggered by oxidative processes.
