Plants and insects coevolved as an evolutionarily successful and enduring association. The molecular arms race led to evolutionary novelties regarding unique mechanisms of defence and detoxification in plants and insects. While insects adopt mechanisms to conquer host defence, trees develop well-orchestrated and species-specific defence strategies against insect herbivory. However, current knowledge on the molecular underpinnings of fine-tuned tree defence responses against different herbivore insects is still restricted. In the current study, using a multi-omics approach, we unveiled the defence response of Populus tremula against aphids (Chaitophorus populialbae) and spongy moths (Lymantria dispar) herbivory. Comparative differential gene expression (DGE) analyses revealed that around 272 and 1203 transcripts were differentially regulated in P. tremula after moth and aphid herbivory compared to uninfested controls. Interestingly, 5716 transcripts were differentially regulated in P. tremula between aphids and moth infestation. Further investigation showed that defence-related stress hormones and their lipid precursors, transcription factors, and signalling molecules were over-expressed, whereas the growth-related counterparts were suppressed in P. tremula after aphid and moth herbivory. Metabolomics analysis documented that around 37% of all significantly abundant metabolites were associated with biochemical pathways related to tree growth and defence. However, the metabolic profiles of aphid and moth-fed trees were quite distinct, indicating species-specific response optimization. After identifying the suitable reference genes in P. tremula, the omics data were further validated using RT-qPCR. Nevertheless, our findings documented species-specific fine-tuning of the defence response of P. tremula, showing conservation on resource allocation for defence overgrowth under aphid and moth herbivory. Such findings can be exploited to enhance our current understanding of molecular orchestration of tree responses against herbivory and aid in developing insect pest resistance P. tremula varieties.

• Klíčová slova
• Populus tremula, RT-qPCR, aphids, induced defence, reference gene analysis, spongy moth, transcriptome and metabolomics,
• MeSH
• býložravci * MeSH
• metabolom MeSH
• metabolomika metody   MeSH
• mšice * fyziologie   MeSH
• můry * fyziologie   genetika   MeSH
• Populus * genetika   parazitologie   metabolismus   MeSH
• regulace genové exprese u rostlin * MeSH
• stanovení celkové genové exprese MeSH
• transkriptom * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Studies of vitality/mortality of cortex cells, as well as of the concentrations of ethylene (ETH), gibberellins (GAs), indolic compounds/auxins (ICs/AUXs) and cytokinins (CKs), were undertaken to explain the hormonal background of kinetin (Kin)-regulated cell death (RCD), which is induced in the cortex of the apical parts of roots of faba bean (Vicia faba ssp. minor) seedlings. Quantification was carried out with fluorescence microscopy, ETH sensors, spectrophotometry and ultrahigh-performance liquid chromatography tandem mass spectrometry (UHPLC‒MS/MS). The results indicated that Kin was metabolized to the transport form, i.e., kinetin-9-glucoside (Kin9G) and kinetin riboside (KinR). KinR was then converted to cis-zeatin (cZ) in apical parts of roots with meristems, to cis-zeatin riboside (cZR) in apical parts of roots without meristems and finally to cis-zeatin riboside 5'-monophosphate (cZR5'MP), which is indicated to be a ligand of cytokinin-dependent receptors inducing CD. The process may be enhanced by an increase in the amount of dihydrozeatin riboside (DHZR) as a byproduct of the pathway of zeatin metabolism. It seems that crosstalk of ETH, ICs/AUXs, GAs and CKs with the cZR5'MP, the cis-zeatin-dependent pathway, but not the trans-zeatin-dependent pathway, is responsible for Kin-RCD, indicating that the process is very specific and offers a useful model for studies of CD hallmarks in plants.

• MeSH
• buněčná smrt MeSH
• cytokininy metabolismus   MeSH
• kinetin farmakologie   MeSH
• kyseliny indoloctové MeSH
• semenáček metabolismus   MeSH
• tandemová hmotnostní spektrometrie MeSH
• Vicia faba * metabolismus   MeSH
• zeatin metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cytokininy MeSH
• kinetin MeSH
• kyseliny indoloctové MeSH
• zeatin MeSH

Plants can acquire an improved resistance against pathogen attacks by exogenous application of natural or artificial compounds. In a process called chemical priming, application of these compounds causes earlier, faster and/or stronger responses to pathogen attacks. The primed defense may persist over a stress-free time (lag phase) and may be expressed also in plant organs that have not been directly treated with the compound. This review summarizes the current knowledge on the signaling pathways involved in chemical priming of plant defense responses to pathogen attacks. Chemical priming in induced systemic resistance (ISR) and systemic acquired resistance (SAR) is highlighted. The roles of the transcriptional coactivator NONEXPRESSOR OF PR1 (NPR1), a key regulator of plant immunity, induced resistance (IR) and salicylic acid signaling during chemical priming are underlined. Finally, we consider the potential usage of chemical priming to enhance plant resistance to pathogens in agriculture.

• Klíčová slova
• Arabidopsis thaliana, biotic stress, chemical priming, defense priming, induced systemic resistance, pathogen attack, priming, systemic acquired resistance,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Global warming is predicted to change the growth conditions for plants and crops in regions at high latitudes (>60° N), including the Arctic. This will be accompanied by alterations in the composition of natural plant and pest communities, as herbivorous arthropods will invade these regions as well. Interactions between previously non-overlapping species may occur and cause new challenges to herbivore attack. However, plants growing at high latitudes experience less herbivory compared to plants grown at lower latitudes. We hypothesize that this finding is due to a gradient of constitutive chemical defense towards the Northern regions. We further hypothesize that higher level of defensive compounds is mediated by higher level of the defense-related phytohormone jasmonate. Because its biosynthesis is light dependent, Arctic summer day light conditions can promote jasmonate accumulation and, hence, downstream physiological responses. A pilot study with bilberry (Vaccinium myrtillus) plants grown under different light regimes supports the hypothesis.

• Klíčová slova
• climate change, jasmonate signaling, light regime, pest distribution, plant defense,
• Publikační typ
• časopisecké články MeSH

BACKGROUND AND AIMS: We have recently shown that an Arabidopsis thaliana double mutant of type III phosphatidylinositol-4-kinases (PI4Ks), pi4kβ1β2, constitutively accumulated a high level of salicylic acid (SA). By crossing this pi4kβ1β2 double mutant with mutants impaired in SA synthesis (such as sid2 impaired in isochorismate synthase) or transduction, we demonstrated that the high SA level was responsible for the dwarfism phenotype of the double mutant. Here we aimed to distinguish between the SA-dependent and SA-independent effects triggered by the deficiency in PI4Kβ1 and PI4Kβ2. METHODS: To achieve this we used the sid2pi4kβ1β2 triple mutant. High-throughput analyses of phytohormones were performed on this mutant together with pi4kβ1β2 and sid2 mutants and wild-type plants. Responses to pathogens, namely Hyaloperonospora arabidopsidis, Pseudomonas syringae and Botrytis cinerea, and also to the non-host fungus Blumeria graminis, were also determined. Callose accumulation was monitored in response to flagellin. KEY RESULTS: We show here the prominent role of high SA levels in influencing the concentration of many other tested phytohormones, including abscisic acid and its derivatives, the aspartate-conjugated form of indole-3-acetic acid and some cytokinins such as cis-zeatin. We show that the increased resistance of pi4kβ1β2 plants to the host pathogens H. arabidopsidis, P. syringae pv. tomato DC3000 and Bothrytis cinerea is dependent on accumulation of high SA levels. In contrast, accumulation of callose in pi4kβ1β2 after flagellin treatment was independent of SA. Concerning the response to Blumeria graminis, both callose accumulation and fungal penetration were enhanced in the pi4kβ1β2 double mutant compared to wild-type plants. Both of these processes occurred in an SA-independent manner. CONCLUSIONS: Our data extensively illustrate the influence of SA on other phytohormone levels. The sid2pi4kβ1β2 triple mutant revealed the role of PI4Kβ1/β2 per se, thus showing the importance of these enzymes in plant defence responses.

• Klíčová slova
• Arabidopsis thaliana, biotic stress, callose, isochorismate synthase 1, pathogens, phytohormones, pi4kβ1β2/PI4Ks, salicylic acid,
• MeSH
• 1-fosfatidylinositol-4-kinasa * MeSH
• Arabidopsis * MeSH
• kyselina salicylová MeSH
• mutace MeSH
• nemoci rostlin MeSH
• proteiny huseníčku genetika   MeSH
• Pseudomonas syringae MeSH
• regulace genové exprese u rostlin MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 1-fosfatidylinositol-4-kinasa * MeSH
• AT5G09350 protein, Arabidopsis MeSH Prohlížeč
• AT5G64070 protein, Arabidopsis MeSH Prohlížeč
• kyselina salicylová MeSH
• proteiny huseníčku MeSH

The phytohormone salicylic acid (SA) has a crucial role in plant physiology. Its role is best described in the context of plant response to pathogen attack. During infection, SA is rapidly accumulated throughout the green tissues and is important for both local and systemic defences. However, some genetic/metabolic variations can also result in SA overaccumulation in plants, even in basal conditions. To date, more than forty Arabidopsis thaliana mutants have been described as having enhanced endogenous SA levels or constitutively activated SA signalling pathways. In this study, we established a collection of mutants containing different SA levels due to diverse genetic modifications and distinct gene functions. We chose prototypic SA-overaccumulators (SA-OAs), such as bon1-1, but also "non-typical" ones such as exo70b1-1; the selection of OA is accompanied by their crosses with SA-deficient lines. Here, we extensively studied the plant development and SA level/signalling under various growth conditions in soil and in vitro, and showed a strong negative correlation between rosette size, SA content and PR1/ICS1 transcript signature. SA-OAs (namely cpr5, acd6, bon1-1, fah1/fah2 and pi4kβ1β2) had bigger rosettes under high light conditions, whereas WT plants did not. Our data provide new insights clarifying a link between SA and plant behaviour under environmental stresses. The presented SA mutant collection is thus a suitable tool to shed light on the mechanisms underlying trade-offs between growth and defence in plants.

• Klíčová slova
• Arabidopsis mutants, Salicylic acid, gene transcription, growth, light,
• MeSH
• Arabidopsis genetika   metabolismus   mikrobiologie   MeSH
• interakce hostitele a patogenu MeSH
• kyselina salicylová metabolismus   MeSH
• mutace * MeSH
• nemoci rostlin genetika   mikrobiologie   MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• regulace genové exprese u rostlin * MeSH
• regulátory růstu rostlin metabolismus   MeSH
• signální transdukce genetika   MeSH
• vývoj rostlin genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• kyselina salicylová MeSH
• proteiny huseníčku MeSH
• regulátory růstu rostlin 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

Viroids are small non-capsidated, single-stranded, covalently-closed circular noncoding RNA replicons of 239-401 nucleotides that exploit host factors for their replication, and some cause disease in several economically important crop plants, while others appear to be benign. The proposed mechanisms of viroid pathogenesis include direct interaction of the genomic viroid RNA with host factors and post-transcriptional or transcriptional gene silencing via viroid-derived small RNAs (vd-sRNAs) generated by the host defensive machinery. Humulus lupulus (hop) plants are hosts to several viroids among which Hop latent viroid (HLVd) and Citrus bark cracking viroid (CBCVd) are attractive model systems for the study of viroid-host interactions due to the symptomless infection of the former and severe symptoms induced by the latter in this indicator host. To better understand their interactions with hop plant, a comparative transcriptomic analysis based on RNA sequencing (RNA-seq) was performed to reveal the transcriptional alterations induced as a result of single HLVd and CBCVd infection in hop. Additionally, the effect of HLVd on the aggressiveness of CBCVd that underlies severe stunting in hop in a mixed infection was studied by transcriptomic analysis. Our analysis revealed that CBCVd infection resulted in dynamic changes in the activity of genes as compared to single HLVd infection and their mixed infection. The differentially expressed genes that are involved in defense, phytohormone signaling, photosynthesis and chloroplasts, RNA regulation, processing and binding; protein metabolism and modification; and other mechanisms were more modulated in the CBCVd infection of hop. Nevertheless, Gene Ontology (GO) classification and pathway enrichment analysis showed that the expression of genes involved in the proteolysis mechanism is more active in a mixed infection as compared to a single one, suggesting co-infecting viroids may result in interference with host factors more prominently. Collectively, our results provide a deep transcriptome of hop and insight into complex single HLVd, CBCVd, and their coinfection in hop-plant interactions.

• Klíčová slova
• Citrus bark cracking viroid, Hop latent viroid, Humulus lupulus, co-infection, differentially expressed genes, transcriptome profiling,
• MeSH
• Humulus genetika   virologie   MeSH
• nemoci rostlin genetika   virologie   MeSH
• transkriptom * MeSH
• viroidy patogenita   MeSH
• Publikační typ
• časopisecké články MeSH

BACKGROUND AND AIMS: Selected beneficial Pseudomonas spp. strains have the ability to influence root architecture in Arabidopsis thaliana by inhibiting primary root elongation and promoting lateral root and root hair formation. A crucial role for auxin in this long-term (1week), long-distance plant-microbe interaction has been demonstrated. METHODS: Arabidopsis seedlings were cultivated in vitro on vertical plates and inoculated with pathogenic strains Pseudomonas syringae pv. maculicola (Psm) and P. syringae pv. tomato DC3000 (Pst), as well as Agrobacterium tumefaciens (Atu) and Escherichia coli (Eco). Root hair lengths were measured after 24 and 48h of direct exposure to each bacterial strain. Several Arabidopsis mutants with impaired responses to pathogens, impaired ethylene perception and defects in the exocyst vesicle tethering complex that is involved in secretion were also analysed. KEY RESULTS: Arabidopsis seedling roots infected with Psm or Pst responded similarly to when infected with plant growth-promoting rhizobacteria; root hair growth was stimulated and primary root growth was inhibited. Other plant- and soil-adapted bacteria induced similar root hair responses. The most compromised root hair growth stimulation response was found for the knockout mutants exo70A1 and ein2. The single immune pathways dependent on salicylic acid, jasmonic acid and PAD4 are not directly involved in root hair growth stimulation; however, in the mutual cross-talk with ethylene, they indirectly modify the extent of the stimulation of root hair growth. The Flg22 peptide does not initiate root hair stimulation as intact bacteria do, but pretreatment with Flg22 prior to Psm inoculation abolished root hair growth stimulation in an FLS2 receptor kinase-dependent manner. These early response phenomena are not associated with changes in auxin levels, as monitored with the pDR5::GUS auxin reporter. CONCLUSIONS: Early stimulation of root hair growth is an effect of an unidentified component of living plant pathogenic bacteria. The root hair growth response is triggered in the range of hours after bacterial contact with roots and can be modulated by FLS2 signalling. Bacterial stimulation of root hair growth requires functional ethylene signalling and an efficient exocyst-dependent secretory machinery.

• Klíčová slova
• Arabidopsis, Flg22, Pseudomonas, Root hair, dde2/ein2/pad4/sid2, exocyst, vesicle trafficking,
• MeSH
• Arabidopsis genetika   růst a vývoj   mikrobiologie   MeSH
• genový knockout MeSH
• interakce hostitele a patogenu * MeSH
• kořeny rostlin růst a vývoj   mikrobiologie   MeSH
• mutace MeSH
• proteinkinasy genetika   MeSH
• proteiny huseníčku genetika   MeSH
• Pseudomonas syringae * MeSH
• receptory buněčného povrchu genetika   MeSH
• regulace genové exprese u rostlin MeSH
• signální transdukce MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• EIN2 protein, Arabidopsis MeSH Prohlížeč
• EXO70A1 protein, Arabidopsis MeSH Prohlížeč
• FLS2 protein, Arabidopsis MeSH Prohlížeč
• proteinkinasy MeSH
• proteiny huseníčku MeSH
• receptory buněčného povrchu MeSH

BACKGROUND AND AIMS: Current strategies for increased crop protection of susceptible tomato plants against pathogen infections include treatment with synthetic chemicals, application of natural pathogen-derived compounds or transfer of resistance genes from wild tomato species within breeding programmes. In this study, a series of 45 genes potentially involved in defence mechanisms was retrieved from the genome sequence of inbred reference tomato cultivar Solanum lycopersicum 'Heinz 1706'. The aim of the study was to analyse expression of these selected genes in wild and cultivated tomato plants contrasting in resistance to the biotrophic pathogen Oidium neolycopersici , the causative agent of powdery mildew. Plants were treated either solely with potential resistance inducers or by inducers together with the pathogen. METHODS: The resistance against O. neolycopersici infection as well as RT-PCR-based analysis of gene expression in response to the oomycete elicitor oligandrin and chemical agent β-aminobutyric acid (BABA) were investigated in the highly susceptible domesticated inbred genotype Solanum lycopersicum 'Amateur' and resistant wild genotype Solanum habrochaites . KEY RESULTS: Differences in basal expression levels of defensins, germins, β-1,3-glucanases, heveins, chitinases, osmotins and PR1 proteins in non-infected and non-elicited plants were observed between the highly resistant and susceptible genotypes. Moreover, these defence genes showed an extensive up-regulation following O. neolycopersici infection in both genotypes. Application of BABA and elicitin induced expression of multiple defence-related transcripts and, through different mechanisms, enhanced resistance against powdery mildew in the susceptible tomato genotype. CONCLUSIONS: The results indicate that non-specific resistance in the resistant genotype S. habrochaites resulted from high basal levels of transcripts with proven roles in defence processes. In the susceptible genotype S. lycopersicum 'Amateur', oligandrin- and BABA-induced resistance involved different signalling pathways, with BABA-treated leaves displaying direct activation of the ethylene-dependent signalling pathway, in contrast to previously reported jasmonic acid-mediated signalling for elicitins.

• Klíčová slova
• BABA, Solanum habrochaites, Solanum lycopersicum, defence genes, ethylene, Oidium neolycopersici, oligandrin, powdery mildew, resistance, tomato,
• MeSH
• aminobutyráty farmakologie   MeSH
• Ascomycota fyziologie   MeSH
• kvantitativní polymerázová řetězová reakce MeSH
• nemoci rostlin imunologie   mikrobiologie   MeSH
• odolnost vůči nemocem MeSH
• regulace genové exprese u rostlin * MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• sekvenční analýza DNA MeSH
• seskviterpeny farmakologie   MeSH
• Solanum lycopersicum genetika   imunologie   mikrobiologie   MeSH
• Solanum genetika   imunologie   mikrobiologie   MeSH
• upregulace MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 3-aminobutyric acid MeSH Prohlížeč
• aminobutyráty MeSH
• oligandrin MeSH Prohlížeč
• rostlinné proteiny MeSH
• seskviterpeny MeSH