The involvement of cytokinins (CK) in biotic stresses has been recognized, while knowledge regarding the effects of CK deficiency on plant response against pathogens is less abundant. Thus, the purpose of this study was to reveal the effects of CK deficiency on proteomics and metabolomic responses of flg22-triggered immunity. We conducted a series of histochemical assays to investigate the activity of the downstream pathways caused by flg22, such as accumulation of ROS, induction of defence genes, and callose deposition, that occurred in Arabidopsis thaliana transgenic lines overexpressing the Hordeum vulgare CKX2 gene (HvCKX2), which are therefore CK-deficient. We also used GC and LC-MS-based technology to quantify variations in stress hormone levels and metabolomic and proteomic responses in flg22-treated HvCKX2 and wild-type Arabidopsis plants. We found that CK deficiency alters the flg22-triggered plant defence response, especially through induction of callose deposition, upregulation of defence response-related proteins, increased amino acid biosynthesis, and regulation of plant photosynthesis. We also indicated that JA might be an important contributor to immune response in plants deficient in CKs. The present study offers new evidence on the fundamental role of endogenous CK in the response to pathogens, as well as the possibility of altering plant biotic tolerance by manipulating CK pools.

• Klíčová slova
• Arabidopsis thaliana, Flg22 peptide, cytokinin, defence response, metabolome, proteome,
• Publikační typ
• časopisecké články MeSH

Plant hormones regulate numerous developmental and physiological processes. Abiotic stresses considerably affect production and distribution of phytohormones as the stress signal triggers. The homeostasis of plant hormones is controlled by their de novo synthesis and catabolism. The aim of this work was to analyse the contents of total and individual groups of endogenous cytokinins (CKs) as well as indole-3-acetic acid (IAA) in AtCKX overexpressing centaury plants grown in vitro on graded NaCl concentrations (0, 50, 100, 150, 200 mM). The levels of endogenous stress hormones including abscisic acid (ABA), salicylic acid (SA) and jasmonic acid (JA) were also detected. The elevated contents of total CKs were found in all analysed centaury shoots. Furthermore, increased amounts of all five CK groups, as well as enhanced total CKs were revealed on graded NaCl concentrations in non-transformed and AtCKX roots. All analysed AtCKX centaury lines exhibited decreased amounts of endogenous IAA in shoots and roots. Consequently, the IAA/bioactive CK forms ratios showed a significant variation in the shoots and roots of all AtCKX lines. In shoots and roots of both non-transformed and AtCKX transgenic centaury plants, salinity was associated with an increase of ABA and JA and a decrease of SA content.

• MeSH
• Centaurium růst a vývoj   metabolismus   MeSH
• cyklopentany analýza   metabolismus   MeSH
• cytokininy analýza   metabolismus   MeSH
• kořeny rostlin růst a vývoj   metabolismus   MeSH
• kyselina abscisová analýza   metabolismus   MeSH
• kyselina salicylová metabolismus   MeSH
• kyseliny indoloctové analýza   metabolismus   MeSH
• oxylipiny analýza   metabolismus   MeSH
• regulátory růstu rostlin analýza   metabolismus   MeSH
• solný stres * MeSH
• techniky in vitro MeSH
• výhonky rostlin růst a vývoj   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cyklopentany MeSH
• cytokininy MeSH
• indoleacetic acid MeSH Prohlížeč
• jasmonic acid MeSH Prohlížeč
• kyselina abscisová MeSH
• kyselina salicylová MeSH
• kyseliny indoloctové MeSH
• oxylipiny MeSH
• regulátory růstu rostlin MeSH

The use of plant biostimulants contributes to more sustainable and environmentally friendly farming techniques and offers a sustainable alternative to mitigate the adverse effects of stress. Protein hydrolysate-based biostimulants have been described to promote plant growth and reduce the negative effect of abiotic stresses in different crops. However, limited information is available about their mechanism of action, how plants perceive their application, and which metabolic pathways are activating. Here we used a multi-trait high-throughput screening approach based on simple RGB imaging and combined with untargeted metabolomics to screen and unravel the mode of action/mechanism of protein hydrolysates in Arabidopsis plants grown in optimal and in salt-stress conditions (0, 75, or 150 mM NaCl). Eleven protein hydrolysates from different protein sources were used as priming agents in Arabidopsis seeds in three different concentrations (0.001, 0.01, or 0.1 μl ml-1). Growth and development-related traits as early seedling establishment, growth response under stress and photosynthetic performance of the plants were dynamically scored throughout and at the end of the growth period. To effectively classify the functional properties of the 11 products a Plant Biostimulant Characterization (PBC) index was used, which helped to characterize the activity of a protein hydrolysate based on its ability to promote plant growth and mitigate stress, and to categorize the products as plant growth promoters, growth inhibitors and/or stress alleviator. Out of 11 products, two were identified as highly effective growth regulators and stress alleviators because they showed a PBC index always above 0.51. Using the untargeted metabolomics approach, we showed that plants primed with these best performing biostimulants had reduced contents of stress-related molecules (such as flavonoids and terpenoids, and some degradation/conjugation compounds of phytohormones such as cytokinins, auxins, gibberellins, etc.), which alleviated the salt stress response-related growth inhibition.

• Klíčová slova
• high-throughput phenotyping, multi- well plates, plant biostimulant characterization index, protein hydrolysates, salinity, secondary metabolism, seed priming,
• Publikační typ
• časopisecké články MeSH

Cytokinin is a phytohormone involved in the regulation of diverse developmental and physiological processes in plants. Its potential in biotechnology and for development of higher-yield and more resilient plants has been recognized, yet the molecular mechanisms behind its action are far from understood. In this report, the roots of barley seedlings were explored as a new source to reveal as yet unknown cytokinin-responsive proteins for crop improvement. Here we found significant differences reproducibly observed for 178 proteins, for which some of the revealed cytokinin-responsive pathways were confirmed in metabolome analysis, including alterations phenylpropanoid pathway, amino acid biosynthesis and ROS metabolism. Bioinformatics analysis indicated a significant overlap between cytokinin response and response to abiotic stress. This was confirmed by comparing proteome and metabolome profiles in response to drought, salinity or a period of temperature stress. The results illustrate complex abiotic stress response in the early development of model crop plant and confirm an extensive crosstalk between plant hormone cytokinin and response to temperature stimuli, water availability or salinity stress.

• Klíčová slova
• Hordeum vulgare, ROS, abiotic stress, metabolome, phenylpropanoid biosynthesis, proteome, root, zeatin,
• Publikační typ
• časopisecké články MeSH

BACKGROUND: The hop plant (Humulus lupulus L.) is a valuable source of several secondary metabolites, such as flavonoids, bitter acids, and essential oils. These compounds are widely implicated in the beer brewing industry and are having potential biomedical applications. Several independent breeding programs around the world have been initiated to develop new cultivars with enriched lupulin and secondary metabolite contents but met with limited success due to several constraints. In the present work, a pioneering attempt has been made to overexpress master regulator binary transcription factor complex formed by HlWRKY1 and HlWDR1 using a plant expression vector to enhance the level of prenylflavonoid and bitter acid content in the hop. Subsequently, we performed transcriptional profiling using high-throughput RNA-Seq technology in leaves of resultant transformants and wild-type hop to gain in-depth information about the genome-wide functional changes induced by HlWRKY1 and HlWDR1 overexpression. RESULTS: The transgenic WW-lines exhibited an elevated expression of structural and regulatory genes involved in prenylflavonoid and bitter acid biosynthesis pathways. In addition, the comparative transcriptome analysis revealed a total of 522 transcripts involved in 30 pathways, including lipids and amino acids biosynthesis, primary carbon metabolism, phytohormone signaling and stress responses were differentially expressed in WW-transformants. It was apparent from the whole transcriptome sequencing that modulation of primary carbon metabolism and other pathways by HlWRKY1 and HlWDR1 overexpression resulted in enhanced substrate flux towards secondary metabolites pathway. The detailed analyses suggested that none of the pathways or genes, which have a detrimental effect on physiology, growth and development processes, were induced on a genome-wide scale in WW-transgenic lines. CONCLUSIONS: Taken together, our results suggest that HlWRKY1 and HlWDR1 simultaneous overexpression positively regulates the prenylflavonoid and bitter acid biosynthesis pathways in the hop and thus these transgenes are presented as prospective candidates for achieving enhanced secondary metabolite content in the hop.

• Klíčová slova
• Bitter acids, Flavonoids, Genetic transformation, Humulus lupulus, Secondary metabolite, Transcription factors, Transcriptome analysis,
• MeSH
• anotace sekvence MeSH
• exprese genu MeSH
• geneticky modifikované rostliny MeSH
• genomika * MeSH
• Humulus genetika   MeSH
• rostlinné proteiny genetika   MeSH
• stanovení celkové genové exprese * MeSH
• transkripční faktory genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• rostlinné proteiny MeSH
• transkripční faktory MeSH

Cytokinin is a multifaceted plant hormone that plays major roles not only in diverse plant growth and development processes, but also stress responses. We summarize knowledge of the roles of its metabolism, transport, and signalling in responses to changes in levels of both macronutrients (nitrogen, phosphorus, potassium, sulphur) and micronutrients (boron, iron, silicon, selenium). We comment on cytokinin's effects on plants' xenobiotic resistance, and its interactions with light, temperature, drought, and salinity signals. Further, we have compiled a list of abiotic stress-related genes and demonstrate that their expression patterns overlap with those of cytokinin metabolism and signalling genes.

• Klíčová slova
• abiotic stress, cytokinin, drought, nutrient, stress tolerance, temperature,
• MeSH
• aklimatizace MeSH
• cirkadiánní hodiny MeSH
• cytokininy metabolismus   MeSH
• fyziologický stres * MeSH
• fyziologie rostlin * MeSH
• období sucha MeSH
• regulace genové exprese u rostlin MeSH
• rostliny genetika   metabolismus   MeSH
• salinita MeSH
• signální transdukce * MeSH
• světlo MeSH
• teplota MeSH
• vývoj rostlin MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• cytokininy MeSH

Plant growth and development are critically influenced by unpredictable abiotic factors. To survive fluctuating changes in their environments, plants have had to develop robust adaptive mechanisms. The dynamic and complementary actions of the auxin and cytokinin pathways regulate a plethora of developmental processes, and their ability to crosstalk makes them ideal candidates for mediating stress-adaptation responses. Other crucial signaling molecules responsible for the tremendous plasticity observed in plant morphology and in response to abiotic stress are reactive oxygen species (ROS). Proper temporal and spatial distribution of ROS and hormone gradients is crucial for plant survival in response to unfavorable environments. In this regard, the convergence of ROS with phytohormone pathways acts as an integrator of external and developmental signals into systemic responses organized to adapt plants to their environments. Auxin and cytokinin signaling pathways have been studied extensively. Nevertheless, we do not yet understand the impact on plant stress tolerance of the sophisticated crosstalk between the two hormones. Here, we review current knowledge on the function of auxin and cytokinin in redirecting growth induced by abiotic stress in order to deduce their potential points of crosstalk.

• Klíčová slova
• ROS, abiotic stress, adaptation, auxin, crosstalk, cytokinin, growth,
• MeSH
• biologický transport MeSH
• cytokininy metabolismus   MeSH
• fyziologická adaptace MeSH
• fyziologický stres * MeSH
• fyziologie rostlin * MeSH
• genové regulační sítě MeSH
• kyseliny indoloctové metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin metabolismus   MeSH
• rostliny genetika   metabolismus   MeSH
• signální transdukce MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• cytokininy MeSH
• kyseliny indoloctové MeSH
• regulátory růstu rostlin MeSH

Barley (Hordeum vulgare) is an economically important species, which can be cultivated in environmentally adverse conditions due to its higher tolerance in contrast to other cereal crops. The draft of H. vulgare genome is available already for couple of years; however its functional annotation is still incomplete. All available databases were searched to expand current annotation. The improved annotation was used to describe processes and genes regulated in transgenic lines showing higher tolerance to drought in our associated article, doi:10.1016/j.nbt.2016.01.010 (Vojta et al., 2016) [1]. Here we present whole transcriptome response, using extended annotation, to severe drought stress and subsequent re-watering in wild-type barley plants in stem elongation phase of growth. Up- and down-regulated genes fall into distinct GO categories and these enriched by stress and revitalization are highlighted. Transcriptomic data were evaluated separately for root and aerial tissues.

• Klíčová slova
• Barley, Drought stress, Genome annotation, Re-watering, Transcriptomics,
• Publikační typ
• časopisecké články MeSH