ABSTRACT
Many natural compounds can activate the plant immunity, and for this reason, they have attracted special interest in crop disease management. Previously, we isolated from strawberry leaves an ellagitannin (HeT), which elicits plant defense responses. In this research, we investigated bioactive compounds from field-collected strawberry leaves capable of inducing defense responses in Arabidopsis thaliana against a bacterial pathogen. Methanolic extracts of strawberry leaves sampled at different months were obtained and compared. The highest content of total soluble phenolic compounds was found in the methanolic extracts of leaves sampled in December (DME). The defense response induced in A. thaliana by DME was attributed to two ellagitannins, the HeT and galloyl-HHDP-glucose. Both compounds exhibited phytoprotective effects against Pseudomonas viridiflava and induced the expression of PDF1.2 and PR1 genes. These results provide an economic value to strawberry leaves, normally discarded at the end of the harvest stage of the crop, as a raw material for plant health enhancer bioinputs.
Subject(s)
Fragaria , Fragaria/genetics , Hydrolyzable Tannins , Plant Leaves , Pseudomonas , SeasonsABSTRACT
Plant secondary metabolism produces a variety of tannins that have a wide range of biological activities, including activation of plant defenses and antimicrobial, anti-inflammatory and antitumoral effects. The ellagitannin HeT (1-O-galloyl-2,3;4,6-bis-hexahydroxydiphenoyl-ß-d-glucopyranose) from strawberry leaves elicits a strong plant defense response, and exhibits antimicrobial activity associated to the inhibition of the oxygen consumption, but its mechanism of action is unknown. In this paper we investigate the influence of HeT on bacterial cell membrane integrity and its effect on respiration. A ß-galactosidase unmasking experiment showed that HeT does not disrupt membrane integrity. Raman spectroscopy analysis revealed that HeT strongly interacts with the cell membrane. Spectrochemical analysis indicated that HeT is oxidized in contact with bacterial cell membranes, and functional studies showed that HeT inhibits oxygen consumption, NADH and MTT reduction. These results provide evidence that HeT inhibits the respiratory chain.
ABSTRACT
HeT (1-0-galloyl-2,3; 4,6-bis-hexahydroxydiphenoyl-ß-D-glucopyranose) is a penta-esterified ellagitannin obtained from strawberry leaves. Previous studies have shown that foliar application of HeT prior to inoculation with a virulent pathogen increases the resistance toward Colletotrichum acutatum in strawberry plants and to Xanthomonas citri subsp. citri in lemon plants. In this work we report that HeT induces an immediate leak of electrolytes, the hyperpolarization of the cellular membrane, a rapid Ca2+ influx to the cytoplasm during the first few seconds, which in turn modulates the accumulation of nitric oxide 5â¯min after treatment. At longer times, a biphasic accumulation of H2O2 with peaks at 2 and 5â¯h post treatment could be observed. In addition, HeT elicited the increase of alternative oxidase capacity during the first 12â¯h post treatment.
Subject(s)
Calcium/metabolism , Fragaria/metabolism , Hydrogen Peroxide/metabolism , Hydrolyzable Tannins/pharmacology , Nitric Oxide/metabolism , Calcium Signaling , Electrolytes/metabolism , Fragaria/microbiology , Plant Diseases/microbiology , Xanthomonas/metabolismABSTRACT
In an incompatible interaction between Colletotrichum fragariae and strawberry plants, the accumulation of phenolic compounds in plant leaves was observed. A particularly abundant penta-esterified ellagitannin that accumulated in response to pathogen attack was identified as 1-0-galloyl-2,3;4,6-bis-hexahydroxydiphenoyl-ß-d-glucopyranose (HeT) by mass spectroscopy and nuclear magnetic resonance. Foliar application of purified HeT prior to inoculation with a virulent pathogen was shown to increase resistance toward C. acutatum in strawberry plants and to Xanthomonas citri subsp. citri in lemon plants. The induced resistance in strawberry was associated with a rapid oxidative burst, callose deposition, a transient increase of salicylic acid in phloem, and induction of gene expression responsive to salicylic acid. Results obtained suggested that HeT could be a common plant defense response molecule capable of inducing pathogen resistance in different plant species.
Subject(s)
Fragaria/metabolism , Fragaria/microbiology , Hydrolyzable Tannins/metabolism , Hydrolyzable Tannins/pharmacology , Citrus/metabolism , Citrus/microbiology , Colletotrichum/pathogenicity , Fragaria/drug effects , Gene Expression Regulation, Plant/drug effects , Magnetic Resonance Spectroscopy , Mass Spectrometry , Phloem/metabolism , Salicylic Acid/metabolism , Xanthomonas/pathogenicityABSTRACT
El estudio se ha realizado en el Hospital Hipólito Unanue de Tacna entre octubre de 1996 y febrero de 1997. Se ha comprobado un número de 150 adolescentes embarazadas con sus respectivos grupos de control, formados por adultas embarazadas que se atendieron en el hospital, teniendo como objetivo principal determinar la actitud y el grado de aceptación del embarazo de las adolescentes en comparación con el de las adultas. Se ha demostrado que la edad de mayor incidencia del embarazo fluctúa entre los 17 y 19 años; y el grado de aceptación en la adolescente es de 46.0 por ciento. Cabe resaltar que la incidencia de embarazo en adolescentes en el período de octubre de 1996 y febrero 1997, fue de 19.4 por ciento.
