The technological exploitation of palladium or palladium nanoparticles (PdNPs) is increasing, and their wider usage relates to an unwanted release of pollutants into the environment, raising public health concerns about the infiltration of palladium into the consumption chain. This study focuses on the effect of spherical gold-cored PdNPs of 50 ± 10 nm diameter stabilized by sodium citrate on the interaction between an oilseed rape (Brassica napus) and the fungal pathogen Plenodomus lingam. Pretreatment of B. napus cotyledons with PdNPs suspension 24 h before but not 24 h after inoculation with P. lingam resulted in a decrease in the extent of disease symptoms; however, this effect was caused by Pd2+ ions (35 mg l-1 or 70 mg l-1). Tests to determine any direct antifungal activity on P. lingam in vitro demonstrated that the residual Pd2+ ions present in the PdNP suspension were responsible for the antifungal activity and that PdNPs themselves do not contribute to this effect. Brassica napus plants did not show any symptoms of palladium toxicity in any form. PdNPs/Pd2+ slightly increased the chlorophyll content and the transcription of pathogenesis-related gene 1 (PR1), indicating the activation of the plant defence system. We conclude that the only toxic effect of the PdNP suspension was on P. lingam via ions and that PdNPs/Pd2+ did not have any deleterious effect on the B. napus plants.

• Klíčová slova
• Brassica napus, Leptosphaeria maculans, Palladium, Plenodomus lingam, nanoparticle, plant defence,
• Publikační typ
• časopisecké články MeSH

Natural compounds isolated from macroalgae are promising, ecofriendly, and multifunctional bioinoculants, which have been tested and used in agriculture. Ulvans, for instance, one of the major polysaccharides present in Ulva spp. cell walls, have been tested for their plant growth-promoting properties as well as their ability to activate plant immune defense, on a large variety of crops. Recently, we have characterized for the first time an arabinogalactan protein-like (AGP-like) from Ulva lactuca, which exhibits several features associated to land plant AGPs. In land plant, AGPs were shown to play a role in several plant biological functions, including cell morphogenesis, reproduction, and plant-microbe interactions. Thus, isolated AGP-like proteins may be good candidates for either the plant growth-promoting properties or the activation of plant immune defense. Here, we have isolated an AGP-like enriched fraction from Ulva lactuca and we have evaluated its ability to (i) protect oilseed rape (Brassica napus) cotyledons against Leptosphaeria maculans, and (ii) its ability to activate immune responses. Preventive application of the Ulva AGP-like enriched fraction on oilseed rape, followed by cotyledon inoculation with the fungal hemibiotroph L. maculans, resulted in a major reduction of infection propagation. The noticed reduction correlated with an accumulation of H2O2 in treated cotyledons and with the activation of SA and ET signaling pathways in oilseed rape cotyledons. In parallel, an ulvan was also isolated from Ulva lactuca. Preventive application of ulvan also enhanced plant resistance against L. maculans. Surprisingly, reduction of infection severity was only observed at high concentration of ulvan. Here, no such significant changes in gene expression and H2O2 production were observed. Together, this study indicates that U. lactuca AGP-like glycoproteins exhibit promising elicitor activity and that plant eliciting properties of Ulva extract, might result not only from an ulvan-originated eliciting activities, but also AGP-like originated.

• Klíčová slova
• Arabinogalactan proteins, Ulva lactuca, elicitor, hemibiotrophic fungus, plant defense, plant immunity,
• Publikační typ
• časopisecké články MeSH

Being natural plant antimicrobials, saponins have potential for use as biopesticides. Nevertheless, their activity in plant-pathogen interaction is poorly understood. We performed a comparative study of saponins' antifungal activities on important crop pathogens based on their effective dose (EC50) values. Among those saponins tested, aescin showed itself to be the strongest antifungal agent. The antifungal effect of aescin could be reversed by ergosterol, thus suggesting that aescin interferes with fungal sterols. We tested the effect of aescin on plant-pathogen interaction in two different pathosystems: Brassica napus versus (fungus) Leptosphaeria maculans and Arabidopsis thaliana versus (bacterium) Pseudomonas syringae pv tomato DC3000 (Pst DC3000). We analyzed resistance assays, defense gene transcription, phytohormonal production, and reactive oxygen species production. Aescin activated B. napus defense through induction of the salicylic acid pathway and oxidative burst. This defense response led finally to highly efficient plant protection against L. maculans that was comparable to the effect of fungicides. Aescin also inhibited colonization of A. thaliana by Pst DC3000, the effect being based on active elicitation of salicylic acid (SA)-dependent immune mechanisms and without any direct antibacterial effect detected. Therefore, this study brings the first report on the ability of saponins to trigger plant immune responses. Taken together, aescin in addition to its antifungal properties activates plant immunity in two different plant species and provides SA-dependent resistance against both fungal and bacterial pathogens.

• Klíčová slova
• Arabidopsis thaliana, Brassica napus, EC50, Leptosphaeria maculans, Pseudomonas syringae, fungicide, salicylic acid,
• Publikační typ
• časopisecké články MeSH

The integrity of the actin cytoskeleton is essential for plant immune signalling. Consequently, it is generally assumed that actin disruption reduces plant resistance to pathogen attack. Here, we demonstrate that actin depolymerization induced a dramatic increase in salicylic acid (SA) levels in Arabidopsis thaliana. Transcriptomic analysis showed that the SA pathway was activated due to the action of isochorismate synthase (ICS). The effect was also confirmed in Brassica napus. This raises the question of whether actin depolymerization could, under particular conditions, lead to increased resistance to pathogens. Thus, we explored the effect of pretreatment with actin-depolymerizing drugs on the resistance of Arabidopsis thaliana to the bacterial pathogen Pseudomonas syringae, and on the resistance of an important crop Brassica napus to its natural fungal pathogen Leptosphaeria maculans. In both pathosystems, actin depolymerization activated the SA pathway, leading to increased plant resistance. To our best knowledge, we herein provide the first direct evidence that disruption of the actin cytoskeleton can actually lead to increased plant resistance to pathogens, and that SA is crucial to this process.

• MeSH
• aktiny metabolismus   MeSH
• Arabidopsis metabolismus   mikrobiologie   MeSH
• Ascomycota patogenita   MeSH
• Brassica napus metabolismus   mikrobiologie   MeSH
• intramolekulární transferasy metabolismus   MeSH
• kyselina salicylová metabolismus   MeSH
• nemoci rostlin mikrobiologie   MeSH
• proteiny huseníčku metabolismus   MeSH
• Pseudomonas syringae patogenita   MeSH
• regulace genové exprese u rostlin fyziologie   MeSH
• signální transdukce fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• aktiny MeSH
• intramolekulární transferasy MeSH
• isochorismate synthase MeSH Prohlížeč
• kyselina salicylová MeSH
• proteiny huseníčku MeSH

Hormonal dynamics after Plasmodiophora brassicae infection were compared in two Brassica napus cultivars-more resistant SY Alister and more sensitive Hornet, in order to elucidate responses associated with efficient defense. Both cultivars responded to infection by the early transient elevation of active cytokinins (predominantly cis-zeatin) and auxin indole-3-acetic acid (IAA) in leaves and roots, which was longer in Hornet. Moderate IAA levels in Hornet roots coincided with a high expression of biosynthetic gene nitrilase NIT1 (contrary to TAA1, YUC8, YUC9). Alister had a higher basal level of salicylic acid (SA), and it stimulated its production (via the expression of isochorismate synthase (ICS1)) in roots earlier than Hornet. Gall formation stimulated cytokinin, auxin, and SA levels-with a maximum 22 days after inoculation (dai). SA marker gene PR1 expression was the most profound at the time point where gall formation began, in leaves, roots, and especially in galls. Jasmonic acid (JA) was higher in Hornet than in Alister during the whole experiment. To investigate SA and JA function, SA was applied before infection, and twice (before infection and 15 dai), and JA at 15 dai. Double SA application diminished gall formation in Alister, and JA promoted gall formation in both cultivars. Activation of SA/JA pathways reflects the main differences in clubroot resistance.

• Klíčová slova
• Brassica napus, Plasmodiophora brassicae, auxin, cytokinin, gene expression, jasmonic acid, plant hormone, resistance, salicylic acid,
• MeSH
• aminohydrolasy genetika   MeSH
• Brassica napus růst a vývoj   metabolismus   parazitologie   MeSH
• cyklopentany analýza   MeSH
• cytokininy analýza   MeSH
• intramolekulární transferasy genetika   MeSH
• kořeny rostlin růst a vývoj   metabolismus   parazitologie   MeSH
• kyseliny indoloctové analýza   MeSH
• listy rostlin růst a vývoj   metabolismus   parazitologie   MeSH
• nemoci rostlin parazitologie   MeSH
• odolnost vůči nemocem MeSH
• oxylipiny analýza   MeSH
• Plasmodiophorida patogenita   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin analýza   MeSH
• rostlinné proteiny genetika   MeSH
• vývojová regulace genové exprese MeSH
• Publikační typ
• časopisecké články MeSH
• srovnávací studie MeSH
• Názvy látek
• aminohydrolasy MeSH
• cyklopentany MeSH
• cytokininy MeSH
• intramolekulární transferasy MeSH
• isochorismate synthase MeSH Prohlížeč
• jasmonic acid MeSH Prohlížeč
• kyseliny indoloctové MeSH
• nitrilase MeSH Prohlížeč
• oxylipiny MeSH
• regulátory růstu rostlin MeSH
• rostlinné proteiny MeSH

Among phytohormones, cytokinins (CKs) play an important role in controlling crucial aspects of plant development. Not only plants but also diverse microorganisms are able to produce phytohormones, including CKs, though knowledge concerning their biosynthesis and metabolism is still limited. In this work we demonstrate that the fungus Leptosphaeria maculans, a hemi-biotrophic pathogen of oilseed rape (Brassica napus), causing one of the most damaging diseases of this crop, is able to modify the CK profile in infected B. napus tissues, as well as produce a wide range of CKs in vitro, with the cis-zeatin derivatives predominating. The endogenous CK spectrum of L. maculans in vitro consists mainly of free CK bases, as opposed to plants, where other CK forms are mostly more abundant. Using functional genomics, enzymatic and feeding assays with CK bases supplied to culture media, we show that L. maculans contains a functional: (i) isopentenyltransferase (IPT) involved in cZ production; (ii) adenosine kinase (AK) involved in phosphorylation of CK ribosides to nucleotides; and (iii) CK-degradation enzyme cytokinin oxidase/dehydrogenase (CKX). Our data further indicate the presence of cis-trans isomerase, zeatin O-glucosyltransferase(s) and N6-(Δ2-isopentenyl)adenine hydroxylating enzyme. Besides, we report on a crucial role of LmAK for L. maculans fitness and virulence. Altogether, in this study we characterize in detail the CK metabolism of the filamentous fungi L. maculans and report its two novel components, the CKX and CK-related AK activities, according to our knowledge for the first time in the fungal kingdom. Based on these findings, we propose a model illustrating CK metabolism pathways in L. maculans.

• Klíčová slova
• Leptosphaeria maculans, adenosine kinase, cytokinin, cytokinin oxidase/dehydrogenase, isopentenyltransferase, zeatin cis/trans isomerase,
• Publikační typ
• časopisecké články MeSH

To achieve host colonization, successful pathogens need to overcome plant basal defences. For this, (hemi)biotrophic pathogens secrete effectors that interfere with a range of physiological processes of the host plant. AvrLm4-7 is one of the cloned effectors from the hemibiotrophic fungus Leptosphaeria maculans 'brassicaceae' infecting mainly oilseed rape (Brassica napus). Although its mode of action is still unknown, AvrLm4-7 is strongly involved in L. maculans virulence. Here, we investigated the effect of AvrLm4-7 on plant defence responses in a susceptible cultivar of B. napus. Using two isogenic L. maculans isolates differing in the presence of a functional AvrLm4-7 allele [absence ('a4a7') and presence ('A4A7') of the allele], the plant hormone concentrations, defence-related gene transcription and reactive oxygen species (ROS) accumulation were analysed in infected B. napus cotyledons. Various components of the plant immune system were affected. Infection with the 'A4A7' isolate caused suppression of salicylic acid- and ethylene-dependent signalling, the pathways regulating an effective defence against L. maculans infection. Furthermore, ROS accumulation was decreased in cotyledons infected with the 'A4A7' isolate. Treatment with an antioxidant agent, ascorbic acid, increased the aggressiveness of the 'a4a7' L. maculans isolate, but not that of the 'A4A7' isolate. Together, our results suggest that the increased aggressiveness of the 'A4A7' L. maculans isolate could be caused by defects in ROS-dependent defence and/or linked to suppressed SA and ET signalling. This is the first study to provide insights into the manipulation of B. napus defence responses by an effector of L. maculans.

• Klíčová slova
• AvrLm4-7, Brassica napus, Leptosphaeria, ROS, effector, ethylene, salicylic acid,
• MeSH
• alely MeSH
• antioxidancia farmakologie   MeSH
• Ascomycota účinky léků   izolace a purifikace   metabolismus   MeSH
• Brassica napus účinky léků   růst a vývoj   metabolismus   mikrobiologie   MeSH
• chromatografie kapalinová MeSH
• cyklopentany metabolismus   MeSH
• ethyleny metabolismus   MeSH
• fungální proteiny metabolismus   MeSH
• hmotnostní spektrometrie MeSH
• interakce hostitele a patogenu účinky léků   MeSH
• kotyledon účinky léků   metabolismus   mikrobiologie   MeSH
• kyselina abscisová metabolismus   MeSH
• kyselina askorbová farmakologie   MeSH
• kyselina salicylová metabolismus   MeSH
• oxylipiny metabolismus   MeSH
• peroxid vodíku metabolismus   MeSH
• polymerázová řetězová reakce s reverzní transkripcí MeSH
• regulátory růstu rostlin metabolismus   MeSH
• signální transdukce * účinky léků   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antioxidancia MeSH
• cyklopentany MeSH
• ethyleny MeSH
• fungální proteiny MeSH
• jasmonic acid MeSH Prohlížeč
• kyselina abscisová MeSH
• kyselina askorbová MeSH
• kyselina salicylová MeSH
• oxylipiny MeSH
• peroxid vodíku MeSH
• regulátory růstu rostlin MeSH

BACKGROUND: The use of light emitting diodes (LEDs) brings several key advantages over existing illumination technologies for indoor plant cultivation. Among these are that LEDs have predicted lifetimes from 50-100.000 hours without significant drops in efficiency and energy consumption is much lower compared to traditional fluorescent tubes. Recent advances allow LEDs to be used with customized wavelengths for plant growth. However, most of these LED growth systems use mixtures of chips emitting in several narrow wavelengths and frequently they are not compatible with existing infrastructures. This study tested the growth of five different plant species under phosphor coated LED-chips fitted into a tube with a standard G13 base that provide continuous visible light illumination with enhanced blue and red light. RESULTS: The LED system was characterized and compared with standard fluorescence tubes in the same cultivation room. Significant differences in heat generation between LEDs and fluorescent tubes were clearly demonstrated. Also, LED lights allowed for better control and stability of preset conditions. Physiological properties such as growth characteristics, biomass, and chlorophyll content were measured and the responses to pathogen assessed for five plant species (both the model plants Arabidopsis thaliana, Nicotiana bentamiana and crop species potato, oilseed rape and soybean) under the different illumination sources. CONCLUSIONS: We showed that polychromatic LEDs provide light of sufficient quality and intensity for plant growth using less than 40% of the electricity required by the standard fluorescent lighting under test. The tested type of LED installation provides a simple upgrade pathway for existing infrastructure for indoor plant growth. Interestingly, individual plant species responded differently to the LED lights so it would be reasonable to test their utility to any particular application.

• Klíčová slova
• Arabidopsis thaliana, Fluorescent tubes, LED, Light, Nicotiana bentamiana, Oilseed rape, Plant physiology, Potato, Soybean,
• Publikační typ
• časopisecké články MeSH

Phytohormone salicylic acid (SA) is a crucial component of plant-induced defense against biotrophic pathogens. Although the key players of the SA pathway are known, there are still gaps in the understanding of the molecular mechanism and the regulation of particular steps. In our previous research, we showed in Arabidopsis suspension cells that n-butanol, which specifically modulates phospholipase D activity, significantly suppresses the transcription of the pathogenesis related (PR-1) gene, which is generally accepted as the SA pathway marker. In the presented study, we have investigated the site of n-butanol action in the SA pathway. We were able to show in Arabidopsis plants treated with SA that n-butanol inhibits the transcription of defense genes (PR-1, WRKY38). Fluorescence microscopy of Arabidopsis thaliana mutants expressing 35S::NPR1-GFP (nonexpressor pathogenesis related 1) revealed significantly decreased nuclear localization of NPR1 in the presence of n-butanol. On the other hand, n-butanol did not decrease the nuclear localization of NPR1 in 35S::npr1C82A-GFP and 35S::npr1C216A-GFP mutants constitutively expressing NPR1 monomers. Mass spectrometric analysis of plant extracts showed that n-butanol significantly changes the metabolic fingerprinting while t-butanol had no effect. We found groups of the plant metabolites, influenced differently by SA and n-butanol treatment. Thus, we proposed several metabolites as markers for n-butanol action.

• Klíčová slova
• NPR1, PR-1, metabolome, n-butanol, phospholipase D, salicylic acid, signaling,
• Publikační typ
• časopisecké články MeSH