1,721,019 research outputs found
Transgene pyramiding in wheat: combination of deoxynivalenol detoxification with inhibition of cell wall degrading enzymes to contrast Fusarium Head Blight and Crown Rot
No full textFusarium Head Blight (FHB) and Crown Rot (FCR) are major diseases of wheat crops, causing extensive damages and mycotoxin contamination. In this work, we investigated the possibility to improve resistance to either or both diseases by combining different resistance mechanisms. To this aim, we stacked in the same wheat genotype transgenes controlling the DON-to-D3G conversion by specific UDP-glucosyltransferases (UGT) and the inhibition of cell wall degrading enzymes (CWDEs) by glycosidase inhibitors. We obtained: i) a durum wheat UGT+PMEI double-transgenic line constitutively expressing the HvUGT13248 and AcPMEI genes, coding for a barley UGT and a kiwi pectin methylesterase inhibitor, respectively; ii) a bread wheat UGT+PGIP line, expressing in floral tissues the HvUGT13248 gene and constitutively the PvPGIP2 gene, coding for a bean polygalacturonase inhibiting protein. We observed that both UGT+PMEI and UGT+PGIP plants exhibited increased resistance against Fusarium graminearum in FHB, further reducing by 10-20 % FHB symptoms as compared to the lines carrying the individual transgenes, and of up to 50 % as compared to wild-type plants. On the other hand, double-transgenic UGT+PMEI seedlings exhibited similar FCR symptoms as the UGT single transgenic line after infection with F. culmorum, indicating no contribution of the PMEI transgene to FCR resistance. This result is also supported by the inability of AcPMEI or PvPGIP2, constitutively expressed in durum wheat transgenic lines, to counteract F. graminearum in FCR. We also verified that F. graminearum produces PG and PME activity on infected wheat crown. We conclude that CWDEs inhibition combined with UGT-based DON detoxification contribute in an additive manner to limiting F. graminearum in FHB. Conversely, UGT-based DON detoxification is the only mechanism contributing to resistance observed against FCR. Indeed, the reinforcement of pectin does not enhance resistance against FCR
PvPGIP2 accumulation in specific floral tissues but not in the endosperm limits fusarium graminearum infection in wheat
Full text linkDrought, Waterlogging and Co‐Infection Influence the Severity of Coniella granati and Phytophthora palmivora in Pomegranate and the Biocontrol Efficacy of Bacillus amyloliquefaciens
Full text linkCultivation of pomegranate (Punica granatum) is threatened by the emerging pathogens Coniella granati and Phytophthora palmivora. Whether these microorganisms increase their damage due to simultaneous infection and abiotic stress in pomegranate is unknown. Amylo-X LC is an effective biofungicide based on Bacillus amyloliquefaciens but its efficacy to protect pomegranate from C. granati and P. palmivora if plants are under abiotic stress has not been tested. Therefore, the effects of drought, waterlogging and co-infection on the aggressiveness of these two pathogens and the efficacy of Amylo-X LC were evaluated. Pomegranate trees were subjected to regular watering, drought and waterlogging conditions, treated with Amylo-X LC, and individually or simultaneously inoculated in the stem by C. granati and P. palmivora. Drought experienced by trees limited P. palmivora, while waterlogging favoured C. granati. In combined infections, the presence of P. palmivora amplified the damage caused by C. granati in trees subjected to regular watering and drought. Amylo-X LC proved effective in preventing P. palmivora damage and did not allow the synergistic effect of P. palmivora on C. granati to occur in trees under regular watering and drought. Drought further reduced P. palmivora lesions in plants pretreated with Amylo-X LC compared to those under regular watering. The impact of abiotic stress in pomegranate during C. granati and P. palmivora infections and the efficacy of B. amyloliquefaciens as a potential agent against pomegranate dieback were discussed. We conclude that further efforts to evaluate the efficacy of biological control agents on crops exposed to different environmental scenarios are needed
Durum wheat improvement against fungal pathogens by using protein inhibitors of cell wall degrading enzymes.
No full textBroad-spectrum and durable resistance is one of the most attracting perspective in breeding projects aimed at increasing crop resistance. Since most microbial pathogens need to surmount the plant cell wall to penetrate the host tissue, the reinforcement of this complex compartment should increase the capacity of the host plant to resist the attack of different pathogens.
We pursued this goal by enhancing the host ability to abolish or limit the activity of Cell Wall Degrading Enzymes (CWDEs) secreted by the pathogens during the penetration and colonization of the host tissue. We concentrated our efforts on the containment of the activity of two different CWDEs: the PolyGalacturonases (PGs) and the xylanase inhibitors (XI). PolyGalacturonases (PGs) are among the first CWDEs secreted by fungal pathogens during infection and in some pathosystems they are virulence factors. PGs depolymerize the cell wall pectin, a minor components of the wheat cell wall, and are inhibited by Polygalacturonase Inhibiting proteins (PGIPs). PG activity is also negatively affected by an high degree of pectin methyl esterification. The level of pectin methyl esterification is controlled by the activity of pectin methylesterases (PMEs), which remove the methyl groups, and by its protein inhibitor called Pectin MethylEsterase Inhibitor (PMEI). Thus, indirectly PMEI may negatively affect the activity of PGs by maintaining the pectin with a high degree of methyl esterification. Xylanases are key enzymes in the degradation of arabinoxylans, a main component of the wheat cell wall. These enzymes have been shown to be virulence factors for the fungal pathogens Botrytis cinerea and Mycosphaerella graminicola. The activity of microbial xylanases is controlled in vitro by xylanase inhibitors (XIs) localized in the plant cell wall. However, no evidences in planta for a role of XIs in plant resistance against pathogens have not been reported yet. By using a transgenic approach we showed that PGIP or PMEI can endows durum wheat with new capacities to control the activity of fungal PGs, possibly through a direct interaction or indirectly by modifying the level and pattern of methyl esterification of cell wall pectin. Similarly, transgenic durum wheat plants over-expressing TAXI-III, a member of the TAXI-type XIs, showed new abilities to control fungal xylanases in all tissues, including those that normally do not accumulate this inhibitor. By phytopathogenic tests we demonstrated that these modifications are effective in limiting wheat diseases caused by the fungal pathogens Fusarium graminearum and Bipolaris sorokiniana. We showed also that the reduction of disease symptoms is associated with a reduced accumulation of mycotoxins. In conclusion, these results indicated that the host cell wall polysaccharides, irrespective of their amount and type, plays a key role as functional barrier against different pathogens and that the increased accumulation of glycosidase inhibitors can contribute to maintain their integrity and improve wheat resistance against fungal pathogens
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Immune responses induced by oligogalacturonides are differentially affected by AvrPto and loss of BAK1/BKK1 and PEPR1/PEPR2
Full text linkA perspective for the use of synthetic analogs of the natural peptaibol trichogin GA IV as biopesticides
No full textTrichoderma spp. represent a rich source of bioactive molecules for controlling plant pathogens. As bioactive molecules, antimicrobial peptides (AMPs) are gaining interest as candidates for new eco-friendly plant protection products. Peptaibols are a peculiar class of AMPs with a well-defined helical structure but poor water solubility, which hampers their use in crop protection. Based on these premises, we used a biorational approach to synthesize peptide analogs of the natural peptaibol trichogin GA IV with Gly‐to‐Lys substitutions to enhance water solubility and antimicrobial activity. We obtained several water-soluble analogs with in vitro fungicidal and bactericidal activity. Some of these analogs completely inhibited the growth of the fungus Botrytis cinerea and the sporulation of the oomycete Plasmopara viticola at low micromolar concentrations. The peptide analogs also exerted bactericidal activity against the bacteria Xanthomonas campestris pv. campestris (Xcc), Pseudomonas syringae pv. tomato and P. syringae pv. actinidiae. In growth chamber experiments, the most effective peptides protected grapevine from P. viticola and B. cinerea and cauliflower from Xcc without phytotoxic effects. The microscopic analysis showed different alterations of the cell membrane and the cytoplasm depending on the examined plant pathogen. Finally, in a two-year field trial, one selected peptide resulted as effective as a cupric fungicide in protecting the vineyard from downy mildew
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