1,721,029 research outputs found
Biocontrol: Could the agroecosystem be the starting point for a new human infection? A review
No full textUromyces appendiculatus Infection in BTH-Treated Bean Plants: Ultrastructural Details of a Lost Fight
No full textThe mechanisms of BTH [benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester]-induced resistance against bean rust caused by Uromyces appendiculatus have been explored in Phaseolus vulgaris by light and transmission electron microscopy, following the infection progression in plants challenged 7 days after treatment. While BTH did not affect uredospore germination and fungal penetration in the substomatal cavity, a first impairment to the colonization appeared evident about 48-96 h after inoculation, with alterations of infection hypha structure and reduction in mycelium expansion. No differences were found in this phase regarding the formation and ultrastructure of haustoria in untreated and BTH-treated plants, except for the deposition of electron-opaque material in the extrahaustorial matrix of the latter. A second and decisive impairment in fungal progression was observed at 7-10 days after inoculation when host cell penetrated, or in close contact with the fungal hyphae, were impregnated by phenolic compounds. The same was observed in fungal walls, particularly around haustoria, thus hampering the biotrophic habitus of the fungus and further mycelium spreading. This, in turn, prevented the evasion of fungal reproductive structures, the uredinia, and the appearance of visible symptoms. No particular ultrastructural alterations were observed in most of the penetrated cells, even at late stages of infection, indicating that BTH treatment does not induce host cells to respond with a hypersensitive reaction (HR). A parallel time course of the expression of phenylalanine ammonia lyase (PAL) gene, the key enzyme for the synthesis of phenylpropanoidic phytoalexins and many other phenolics, has shown that PAL mRNA is strongly and persistently transcripted in BTH-treated plants since the 6th h after treatment, though no apparent ultrastructural alterations were detectable up to some days after pathogen challenging. This indicates that BTH, at the employed concentration of 0.3 mM, directly activates the plant's own defences, thus accounting for the observed full protection against bean rust
Analisi e localizzazione di endomannanasi nel seme di Phacelia tanacetifolia nelle prime fasi di germinazione
No full textThe xylanase inhibitor TAXI-III limits cell death induced by a xylanase secreted by Fusarium graminearum during wheat infection.
No full textCereals contain xylanase inhibitor proteins (XIs) which inhibit microbial xylanases from glycoside hydrolase families 10 and 11. In wheat, three types of XIs have been identified: Triticum aestivum XI (TAXI), xylanase inhibitor protein (XIP) and thaumatin-like XI (TLXI). These inhibitors are considered part of the defence mechanisms that plants use to counteract microbial pathogens and recently we provided in planta evidences for the protective role of TAXI-III, a member of the TAXI type XIs. To elucidate the molecular mechanism underlying the capacity of the transgenic plants expressing Taxi-III to limit Fusarium Head Blight (FHB) disease symptoms caused by F. graminearum, we performed infiltration experiments on wheat tissues with a xylanase strongly expressed by F. graminearum during wheat spike infection which we have previously demonstrated to induce cell death and hydrogen peroxide accumulation. Experiments performed on glumes of flowering wheat spikes showed that the presence of TAXI-III significantly decreased cell death and hydrogen peroxide accumulation. Most interestingly, similar results were also obtained by infiltrating the same xylanase on glumes of transgenic wheat plants expressing TAXI-III. These results suggest that the reduced FHB symptoms on transgenic TAXI-III plants can be due to the direct inhibition of xylanase activity secreted by the pathogen but also to the capacity of TAXI-III to prevent the recognition of xylanase by a plant receptor possibly involved in cell death elicitation
Immunolocalization of endo-beta-mannanases in Phacelia tanacetifolia seeds during early phases of germination
No full textThe product of the rice myb7 unspliced mRNA dimerizes with the maize leucine-zipper opaque2 and stimulates its activity in transient expression assay
No full textmyb7 mRNA is present in rice in spliced and unspliced forms, splicing being enhanced by anoxia. The protein (Mybleu) encoded by the unspliced mRNA is composed of an incomplete Myb domain followed by a leucine zipper; however, it lacks canonical sequences for DNA binding, transcriptional activation, and nuclear localization. We show here that in transiently transformed tobacco protoplasts, Mybleu is able to enhance the transcriptional activity of the maize leucine zipper Opaque2 on its target b32 promoter. The Mybleu transactivation effect is strictly dependent on the presence of Opaque2 and is driven by Mybleu-Opaque2 heterodimers. Mybleu is located in the nucleus, both in rice and in transformed tobacco protoplasts. In rice, the protein is expressed in regions corresponding to undifferentiated cells of roots and coleoptiles. Therefore, myb7 mRNA encodes, depending on its splicing, two transcription factors belonging to separate classes. One of them, Myblue, has novel structural characteristics, suggesting the existence of new mechanisms acting in the activation of transcription.
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Acute exposure of the aquatic macrophyte Callitriche obtusangula to the herbicide oxadiazon: The protective role of N-acetylcysteine
No full textIn this study we investigated the acute exposure of the aquatic macrophyte Callitriche obtusangula to the herbicide oxadiazon (Ronstar®). The toxic effects on C. obtusangula were evaluated, 24 h after exposure, by assessing visible necrotic leaf lesions and, 12 h after exposure, via analyses of dead cells and hydrogen peroxide (H2O2) deposits localized by histocytochemical analysis with Trypan blue and 3,3′-diaminobenzidine (DAB), respectively. As a result, we found that 0.1275 μg L-1 a.i. (active ingredient) oxadiazon was the maximum concentration that produced no observable adverse effects (NOAEC) both at leaf and tissue levels, at any considered exposure time. Additionally, we assayed the protective effect of pre-treatment with 0.25 mM N-acetylcysteine (NAC), a cysteine donor, on the damage caused by the toxic herbicidal dose of 6.37 μg L-1 a.i to C. obtusangula, correlating the NAC observed protection to the direct H2O2-scavenging and to the enhancement of glutathione parameters. NAC-treated plants showed a fourfold increase in the GSH (reduced glutathione) + GSSG (oxidised glutathione) content (149.2 nmol g-1 FW) compared to controls (36.1 nmol g-1 FW); in the NAC + oxadiazon treatments, the GSH + GSSG content was more than fivefold higher (202.1 nmol g-1 FW). GSH showed a similar trend in NAC and NAC + oxadiazon treatments, being six- (130.0 nmol g-1 FW) and eightfold (185.0 nmol g-1 FW) higher, respectively, compared to controls (20.7 nmol g-1 FW). Accordingly, the GSH/GSSG ratio in NAC- and NAC + oxadiazon-treated plants was significantly increased compared to controls, indicating alleviation of oxidative stress. © 2008 Elsevier Ltd. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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