Lactoperoxidase is a member of the family of the mammalian heme peroxidases which have a broad spectrum of activity. Their best known effect is their antimicrobial activity that arouses much interest in in vivo and in vitro applications. In this context, the proper use of lactoperoxidase needs a good understanding of its mode of action, of the factors that favor or limit its activity, and of the features and properties of the active molecules. The first part of this review describes briefly the classification of mammalian peroxidases and their role in the human immune system and in host cell damage. The second part summarizes present knowledge on the mode of action of lactoperoxidase, with special focus on the characteristics to be taken into account for in vitro or in vivo antimicrobial use. The last part looks upon the characteristics of the active molecule produced by lactoperoxidase in the presence of thiocyanate and/or iodide with implication(s) on its antimicrobial activity.
Nowadays, the demand for a reduction of chemical pesticides use is growing. In parallel, the development of alternative methods to protect crops from pathogens and pests is also increasing. Essential oil (EO) properties against plant pathogens are well known, and they are recognized as having an interesting potential as alternative plant protection products. In this study, 90 commercially available essential oils have been screened in vitro for antifungal and antibacterial activity against 10 plant pathogens of agronomical importance. EOs have been tested at 500 and 1000 ppm, and measures have been made at three time points for fungi (24, 72 and 120 h of contact) and every two hours for 12 h for bacteria, using Elisa microplates. Among the EOs tested, the ones from Allium sativum, Corydothymus capitatus, Cinnamomum cassia, Cinnamomum zeylanicum, Cymbopogon citratus, Cymbopogon flexuosus, Eugenia caryophyllus, and Litsea citrata were particularly efficient and showed activity on a large panel of pathogens. Among the pathogens tested, Botrytis cinerea, Fusarium culmorum, and Fusarium graminearum were the most sensitive, while Colletotrichum lindemuthianum and Phytophthora infestans were the less sensitive. Some EOs, such as the ones from A. sativum, C. capitatus, C. cassia, C. zeylanicum, C. citratus, C. flexuosus, E. caryophyllus, and L. citrata, have a generalist effect, and are active on several pathogens (7 to 10). These oils are rich in phenols, phenylpropanoids, organosulfur compounds, and/or aldehydes. Others, such as EOs from Citrus sinensis, Melaleucacajputii, and Vanilla fragrans, seem more specific, and are only active on one to three pathogens. These oils are rich in terpenes and aldehydes.
Controlling pests in pre-and postharvest crops using natural and lowimpact products is a major challenge. The lactoperoxidase system is an enzymatic system that exists in all external secretions in mammals and is part of the non-immune system. We tested its efficacy in in vitro microplates on Phytophthora infestans, Penicillium digitatum, Penicillium italicum, Penicillium expansum and Botrytis cinerea to determine the most suitable concentrations for use. Then, we verified its efficacy in planta under controlled conditions. Solutions prepared with 5.4 mM iodide and 1.2 mM thiocyanate and diluted threefold inhibited pathogen growth in vitro by 63-100%. Twofold-diluted solutions protected potato plants against P. infestans by 60-74% under controlled conditions. Undiluted solution inhibited orange's and apple's postharvest pathogens in curative application with efficacy levels ranging between 84 and 95% in orange and between 63 and 74% in apple. 1.5-fold concentrated solutions inhibited postharvest pathogens of apple in curative application with efficacy levels ranging between 84 and 92%. Our results also show that the oxidative stress response of fruit following wounding could interfere with ion efficiency. Our tests demonstrate for the first time that this biochemical method is as efficient as a conventional synthetic chemical method under controlled conditions. 2011). Then, sexual reproduction spread across northern Europe, leading to higher genetic diversity (Cooke et al. 2011;Yuen and Andersson 2013;Wiik 2014). This also increased the capacity of the pathogen to J Phytopathol 165 (2017) 22-34 Ó 2016 Blackwell Verlag GmbH 22 J Phytopathol Penicillium expansum, Penicillium digitatum, Penicillium italicum and Botrytis cinerea cultures Penicillium expansum (CBS 484.75), P. digitatum (MUCL 39704), P. italicum ( MUCL 15608) and B. cinerea strain V (isolated from decayed fruit in our laboratory) were grown on potato dextrose agar at 25°C in a culture chamber. After 10 days (for the Penicillium strains) and 3 weeks (for B. cinerea) of incubation, conidia were collected by adding 9 ml of sterile 0.05% Tween water on the plate. Conidia were scraped off with a sterile inoculating loop and filtered through a sterilized double-layer fine cloth. The
Nucleotide sequences of a broad range of Peach Latent Mosaic Viroid (PLMVd) variants were determined. The variants were isolated from peach, pear, and almond tree samples collected in Tunisia. Sequence analysis confirmed the high variability of PLMVd, as no less than 119 new variants were identified. Variations included new polymorphic positions, insertions of 11 to 14 nucleotides, and new mutations within the hammerhead self-cleavage motifs. We provide the first covariation-based evidence for certain stems within the proposed secondary structure. Our covariation analysis also strengthens the view that a pseudoknot closes the replication domain. On the basis of phylogenetic tree studies and informative positions, PLMVd variants are proposed to cluster into groups and subgroups likely to have resulted from recombination events. PLMVd thus emerges as a suitable viroid for retracing the evolution of an RNA genome.
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