Miroslava Konstantinova Zhiponova
@uni-sofia.bg
Department of Plant Physiology/Faculty of Biology
Sofia University
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
G Ivanov, A Kercheva, A Tosheva, Z Yordanova, and M Zhiponova
IOP Publishing
Abstract Plantago atrata Hoppe (dark plantain; Plantaginaceae) is a lesser-studied narrow-leaved Plantain species and in the present review, we summarize the knowledge about the plant. The distribution of this alpine species and reported subspecies is described. Emphasis is made on P. atrata taxonomic features including botanical characteristics and phylogenetic discrimination via DNA barcoding and metabolic composition. The ecological significance of this plant species is discussed from floristic and nutrient value points of view. The collected information would serve as a basis for further in-depth research on physiological and phytochemical aspects of P. atrata, which would enable the understanding of this plant’s high-altitude adaptation and its possible contribution to beneficial applications for other organisms.
Desislava I. Mantovska, Miroslava K. Zhiponova, Detelina Petrova, Kalina Alipieva, Georgi Bonchev, Irina Boycheva, Yana Evstatieva, Dilyana Nikolova, Ivanka Tsacheva, Svetlana Simova,et al.
MDPI AG
Stachys scardica Griseb. is a Balkan endemic species listed in The Red Data Book of Bulgaria with the conservation status “endangered”. Successful micropropagation was achieved on MS medium supplemented with 1.5 mg/L benzyladenine (BA), followed by a subsequent ex vitro adaptation in an experimental field resulting in 92% regenerated plants. Using nuclear magnetic resonance (NMR), phenylethanoid glycosides (verbascoside, leucosceptoside A), phenolic acids (chlorogenic acid), iridoids (allobetonicoside and 8-OAc-harpagide), and alkaloids (trigonelline) were identified, characteristic of plants belonging to the genus Stachys. High antioxidant and radical scavenging activities were observed in both in situ and ex vitro acclimated S. scardica plants, correlating with the reported high concentrations of total phenols and flavonoids in these variants. Ex vitro adapted plants also exhibited a well-defined anti-inflammatory potential, demonstrating high inhibitory activity against the complement system. Employing a disk diffusion method, a 100% inhibition effect was achieved compared to positive antibiotic controls against Staphylococcus epidermidis and Propionibacterium acnes, with moderate activity against Bacillus cereus. The induced in vitro and ex vitro model systems can enable the conservation of S. scardica in nature and offer future opportunities for the targeted biosynthesis of valuable secondary metabolites, with potential applications in the pharmaceutical and cosmetic industries.
Anna Zaharieva, Krasimir Rusanov, Mila Rusanova, Momchil Paunov, Zhenya Yordanova, Desislava Mantovska, Ivanka Tsacheva, Detelina Petrova, Kiril Mishev, Petre I. Dobrev,et al.
MDPI AG
Nepeta nuda L. is a medicinal plant enriched with secondary metabolites serving to attract pollinators and deter herbivores. Phenolics and iridoids of N. nuda have been extensively investigated because of their beneficial impacts on human health. This study explores the chemical profiles of in vitro shoots and wild-grown N. nuda plants (flowers and leaves) through metabolomic analysis utilizing gas chromatography and mass spectrometry (GC–MS). Initially, we examined the differences in the volatiles’ composition in in vitro-cultivated shoots comparing them with flowers and leaves from plants growing in natural environment. The characteristic iridoid 4a-α,7-β,7a-α-nepetalactone was highly represented in shoots of in vitro plants and in flowers of plants from nature populations, whereas most of the monoterpenes were abundant in leaves of wild-grown plants. The known in vitro biological activities encompassing antioxidant, antiviral, antibacterial potentials alongside the newly assessed anti-inflammatory effects exhibited consistent associations with the total content of phenolics, reducing sugars, and the identified metabolic profiles in polar (organic acids, amino acids, alcohols, sugars, phenolics) and non-polar (fatty acids, alkanes, sterols) fractions. Phytohormonal levels were also quantified to infer the regulatory pathways governing phytochemical production. The overall dataset highlighted compounds with the potential to contribute to N. nuda bioactivity.
Ganka Chaneva, Alexander Tomov, Momchil Paunov, Viktoria Hristova, Valentina Ganeva, Nikolina Mihaylova, Svetoslav Anev, Nikolay Krumov, Zhenya Yordanova, Boris Tsenov,et al.
MDPI AG
Ludisia discolor is commonly known as a jewel orchid due to its variegated leaves. Easy maintenance of the orchid allows it to be used as a test system for various fertilizers and nutrient sources, including aquaponic water (AW). First, we applied DNA barcoding to assess the taxonomic identity of this terrestrial orchid and to construct phylogenetic trees. Next, the vegetative organs (leaf, stem, and root) were compared in terms of the level of metabolites (reducing sugars, proteins, anthocyanins, plastid pigments, phenolics, and antioxidant activity) and nutrient elements (carbon, nitrogen, sodium, and potassium), which highlighted the leaves as most functionally active organ. Subsequently, AW was used as a natural source of fish-derived nutrients, and the orchid growth was tested in hydroponics, in irrigated soil, and in an aquaponic system. Plant physiological status was evaluated by analyzing leaf anatomy and measuring chlorophyll content and chlorophyll fluorescence parameters. These results provided evidence of the beneficial effects of AW on the jewel orchid, including increased leaf formation, enhanced chlorophyll content and photosystems’ productivity, and stimulated and prolonged flowering. The information acquired in the present study could be used in addressing additional aspects of the growth and development of the jewel orchid, which is also known for its medicinal value.
Detelina Petrova, Uroš Gašić, Lyubomira Yocheva, Anton Hinkov, Zhenya Yordanova, Ganka Chaneva, Desislava Mantovska, Momchil Paunov, Lyubomira Ivanova, Mariya Rogova,et al.
Frontiers Media SA
Nepeta nuda (catmint; Lamiaceae) is a perennial medicinal plant with a wide geographic distribution in Europe and Asia. This study first characterized the taxonomic position of N. nuda using DNA barcoding technology. Since medicinal plants are rich in secondary metabolites contributing to their adaptive immune response, we explored the N. nuda metabolic adjustment operating under variable environments. Through comparative analysis of wild-grown and in vitro cultivated plants, we assessed the change in phenolic and iridoid compounds, and the associated immune activities. The wild-grown plants from different Bulgarian locations contained variable amounts of phenolic compounds manifested by a general increase in flowers, as compared to leaves, while a strong reduction was observed in the in vitro plants. A similar trend was noted for the antioxidant and anti-herpesvirus activity of the extracts. The antimicrobial potential, however, was very similar, regardless the growth conditions. Analysis of the N. nuda extracts led to identification of 63 compounds including phenolic acids and derivatives, flavonoids, and iridoids. Quantification of the content of 21 target compounds indicated their general reduction in the extracts from in vitro plants, and only the ferulic acid (FA) was specifically increased. Cultivation of in vitro plants under different light quality and intensity indicated that these variable light conditions altered the content of bioactive compounds, such as aesculin, FA, rosmarinic acid, cirsimaritin, naringenin, rutin, isoquercetin, epideoxyloganic acid, chlorogenic acid. Thus, this study generated novel information on the regulation of N. nuda productivity using light and other cultivation conditions, which could be exploited for biotechnological purposes.
Desislava I. Mantovska, Miroslava K. Zhiponova, Milen I. Georgiev, Kalina Alipieva, Ivanka Tsacheva, Svetlana Simova, and Zhenya P. Yordanova
MDPI AG
Stachys thracica Davidov is a Balkan endemic species distributed in Bulgaria, Greece, and Turkey. In Bulgaria, it is classified as “rare” and is under the protection of the Bulgarian biodiversity law. The aim of our study was to develop an efficient protocol for ex situ conservation of S. thracica and to perform comparative NMR-based metabolite profiling and bioactivity assays of extracts from in situ grown, in vitro cultivated, and ex vitro acclimated plants. Micropropagation of S. thracica was achieved by in vitro cultivation of mono-nodal segments on basal MS medium. Ex vitro adaptation was accomplished in the experimental field with 83% survival while conserved genetic identity between in vitro and ex vitro plants as shown by the overall sequence-related amplified polymorphism marker patterns was established. Verbascoside, chlorogenic acid, and trigonelline appeared the main secondary metabolites in in situ, in vitro cultivated, and ex vitro acclimated S. thracica. High total phenolic and flavonoid content as well as antioxidant and radical scavenging activity were observed in in situ and ex vitro plants. Further, the anti-inflammatory activity of S. thracica was tested by hemolytic assay and a high inhibition of the complement system was observed. Initiated in vitro and ex vitro cultures offer an effective tool for the management and better exploitation of the Stachys secondary metabolism and the selection of lines with high content of bioactive molecules and nutraceuticals.
Anelia Iantcheva, Miroslava Zhiponova, Miglena Revalska, Jefri Heyman, Ivayla Dincheva, Ilian Badjakov, Nathan De Geyter, Irina Boycheva, Sofie Goormachtig, and Lieven De Veylder
Springer Science and Business Media LLC
The F-box domain is a conserved structural protein motif that most frequently interacts with the SKP1 protein, the core of the SCFs (SKP1-CULLIN-F-box protein ligase) E3 ubiquitin protein ligases. As part of the SCF complexes, the various F-box proteins recruit substrates for degradation through ubiquitination. In this study, we functionally characterized an F-box gene (MtF-box) identified earlier in a population of Tnt1 retrotransposon-tagged mutants of Medicago truncatula and its Arabidopsis thaliana homolog (AtF-box) using gain- and loss-of-function plants. We highlighted the importance of MtF-box in leaf development of M. truncatula. Protein-protein interaction analyses revealed the 2-isopropylmalate synthase (IPMS) protein as a common interactor partner of MtF-box and AtF-box, being a key enzyme in the biosynthesis pathway of the branched-chain amino acid leucine. For further detailed analysis, we focused on AtF-box and its role during the cell division cycle. Based on this work, we suggest a mechanism for the role of the studied F-box gene in regulation of leucine homeostasis, which is important for growth.
Zornitsa Karcheva, Zhaneta Georgieva, Alexander Tomov, Detelina Petrova, Miroslava Zhiponova, Ivanina Vasileva, and Ganka Chaneva
Pensoft Publishers
The present study compared the stress response of two microalgal strains – Arthronema africanum (Cyanoprokaryota) and Coelastrella sp. BGV (Chlorophyta), after heavy metals’ treatment. Changes of algal growth, pigment and protein content were analyzed after adding Cu, Cd and Pb (50 µM and 100 µM) to the nutrition medium. It was found that Cd and Pb significantly inhibited growth and protein biosynthesis of microalgae, but the effect of Cu remained less pronounced. In both strains, a decrease of chlorophyll content was observed, while carotenoid content markedly increased, especially in Coelastrella sp. BGV biomass. The addition of 100 µM Cd and 100 µM Pb to the medium caused a strong enhancement of malondialdehyde in both microalgal strains, which corresponded to the significant increase of superoxide dismutase and catalase activity. The antioxidant enzymes appeared to be differently altered by heavy metals’ exposure. The activity of SOD in the Arthronema africanum cells was most strongly affected by Cd, in contrast to Coelastrella sp. BGV that was highly increased by 100 µM Pb. The application of 100 µM Cd and 100 µM Pb increased in a similar manner catalase activity in both microalgae. The strains that were studied showed a high absorption capacity for metal ions, especially for Pb, which was absorbed largely than Cd and Cu. For that reason, we assumed that both microalga and, in particular, Coelastrella sp. BGV, could be successfully used for treatment of contaminated water bodies.
Desislava I. Mantovska, Miroslava K. Zhiponova, Milen I. Georgiev, Tsvetinka Grozdanova, Dessislava Gerginova, Kalina Alipieva, Svetlana Simova, Milena Popova, Veneta M. Kapchina-Toteva, and Zhenya P. Yordanova
MDPI AG
Micropropagation of rare Veronica caucasica M. Bieb. was achieved by successful in vitro cultivation of mono-nodal segments on MS medium supplemented with 1.0 mg L–1 6-benzylaminopurine (BA) and then transferring the regenerated plants on hormone free basal MS medium for root development. In vitro multiplicated plants were successively acclimated in a growth chamber and a greenhouse with 92% survival. The number of plastid pigments and the total phenolics content in in vitro cultivated and ex vitro adapted plants were unchanged, and no accumulation of reactive oxygen species (ROS) was detected by staining with 3-3′-diaminobenzidine (DAB) and 2′,7′-dichlorofluorescein diacetate (DCF-DA). Nuclear Magnetic Resonance (NMR) fingerprinting allowed for the identification of the major alterations in metabolome of V. caucasica plants during the process of ex situ conservation. Iridoid glucosides such as verproside, aucubin and catalpol were characteristic for in vitro cultivated plants, while in ex vitro acclimated plants phenolic acid–protocatechuic acid and caffeic acid appeared dominant. The successful initiation of in vitro and ex vitro cultures is an alternative biotechnological approach for the preservation of V. caucasica and would allow for further studies of the biosynthetic potential of the species and the selection of lines with a high content of pharmaceutically valuable molecules and nutraceuticals.
Miroslava Zhiponova, Jefri Heyman, Lieven De Veylder, and Anelia Iantcheva
Japanese Society for Root Research
Mariana Radkova, Miglena Revalska, Miroslava Zhiponova, and Anelia Iantcheva
Informa UK Limited
Valentina Ganeva, Boyana Angelova, Bojidar Galutzov, Vasilij Goltsev, and Miroslava Zhiponova
Frontiers Media SA
Yeasts are rich source of proteins, antioxidants, vitamins, and other bioactive compounds. The main drawback in their utilization as valuable ingredients in functional foods and dietary supplements production is the thick, indigestible cell wall, as well as the high nucleic acid content. In this study, we evaluated the feasibility of pulsed electric field (PEF) treatment as an alternative method for extraction of proteins and other bioactive intracellular compounds from yeasts. Baker’s yeast water suspensions with different concentration (12.5–85 g dry cell weight per liter) were treated with monopolar rectangular pulses using a continuous flow system. The PEF energy required to achieve irreversible electropermeabilization was significantly reduced with the increase of the biomass concentration. Upon incubation of the permeabilized cells in water, only relatively small intracellular compounds were released. Release of 90% of the free amino acids and low molecular UV absorbing compounds, 80% of the glutathione, and ∼40% of the total phenol content was achieved about 2 h after pulsation and incubation of the suspensions at room temperature. At these conditions, the macromolecules (proteins and nucleic acids) were retained largely inside. Efficient protein release (∼90% from the total soluble protein) occurred only after dilution and incubation of the permeabilized cells in buffer with pH 8–9. Protein concentrates obtained by ultrafiltration (10 kDa cut off) had lower nucleic acid content (protein/nucleic acid ratio ∼100/4.5) in comparison with cell lysates obtained by mechanical disintegration. The obtained results allowed to conclude that PEF treatment can be used as an efficient alternative approach for production of yeast extracts with different composition, suitable for application in food, cosmetics and pharmaceutical industries.
Miroslava Zhiponova, Zhenya Yordanova, Dolja Pavlova, Mariya Rogova, Milena Dimitrova, Daniela Dragolova, Elena Tasheva-Terzieva, and Veneta Kapchina-Toteva
CSIRO Publishing
The genus Teucrium includes perennial herbs or shrubs widespread all around the world. The wall germander (Teucrium chamaedrys L.) is widely used in traditional and modern medicine for various health disorders and recent research revealed that serpentine populations of this herb have increased antioxidant and respective medical potential compared with calcareous population. The present study aims to elucidate further the role of phenolic compounds for T. chamaedrys growth on serpentine soil. Methanol extracts from two serpentine and two non-serpentine (calcareous and siliceous) Bulgarian populations were obtained and analysed for total quantity of phenolics and flavonoids, and antioxidant activity. The serpentine soils acted as an elicitor of the antioxidant response in T. chamaedrys plants and the increased phenolics level correlated with enhanced antioxidant activity. The calcareous population had lower values but still higher than the siliceous population which had the lowest antioxidant values, although the flavonoid quantity that was equal to the serpentine populations. A gas chromatography-mass spectrometry (GC-MS) assay for identifying phenolic acids pointed to caffeic acid as a dominant compound, with additional cinnamic and benzoic acid derivatives with putative roles as antioxidants, in cell wall lignification for heavy metals chelation, and for interspecies interactions.
Valentin Velinov, Irina Vaseva, Grigor Zehirov, Miroslava Zhiponova, Mariana Georgieva, Nick Vangheluwe, Tom Beeckman, and Valya Vassileva
Frontiers Media SA
The family of NudC proteins has representatives in all eukaryotes and plays essential evolutionarily conserved roles in many aspects of organismal development and stress response, including nuclear migration, cell division, folding and stabilization of other proteins. This study investigates an undescribed Arabidopsis homolog of the Aspergillus nidulans NudC gene, named NMig1 (for Nuclear Migration 1), which shares high sequence similarity to other plant and mammalian NudC-like genes. Expression of NMig1 was highly upregulated in response to several abiotic stress factors, such as heat shock, drought and high salinity. Constitutive overexpression of NMig1 led to enhanced root growth and lateral root development under optimal and stress conditions. Exposure to abiotic stress resulted in relatively weaker inhibition of root length and branching in NMig1-overexpressing plants, compared to the wild-type Col-0. The expression level of antioxidant enzyme-encoding genes and other stress-associated genes was considerably induced in the transgenic plants. The increased expression of the major antioxidant enzymes and greater antioxidant potential correlated well with the lower levels of reactive oxygen species (ROS) and lower lipid peroxidation. In addition, the overexpression of NMig1 was associated with strong upregulation of genes encoding heat shock proteins and abiotic stress-associated genes. Therefore, our data demonstrate that the NudC homolog NMig1 could be considered as a potentially important target gene for further use, including breeding more resilient crops with improved root architecture under abiotic stress.
M. ZHIPONOVA, M. PAUNOV, S. ANEV, N. PETROVA, S. KRUMOVA, A. RAYCHEVA, V. GOLTSEV, N. TZVETKOVA, S. TANEVA, K. SAPUNOV,et al.
Institute of Experimental Botany
Light is a major factor controlling plant growth and development. To assess the impact of the applied light conditions, we aimed to sort out a tool for early diagnostics of the plant physiological state. We investigated the effect of a blue:red:far-red LED light formula recommended for improved plant performance (flowering). High (BR) and low (BRS) light intensity variants were compared to normal (W) and 'shadowed' (WS) white fluorescent controls. The efficiency of the JIP-test to determine changes during early growth of pea plants was compared to additional physiological characteristics (growth parameters, thermal stability of the thylakoid membranes, chlorophyll content, CO2 assimilation, transpiration). Our data showed the onset of growth inhibition under BR light, while BRS light stimulated plants to reach the flowering stage similarly as the W control. We concluded that the JIP-test is appropriate for early, reliable, and nondestructive analysis of light recipes for plant growth and flowering.
Anaxi Houbaert, Cheng Zhang, Manish Tiwari, Kun Wang, Alberto de Marcos Serrano, Daniel V. Savatin, Mounashree J. Urs, Miroslava K. Zhiponova, Gustavo E. Gudesblat, Isabelle Vanhoutte,et al.
Springer Science and Business Media LLC
Stomatal cell lineage is an archetypal example of asymmetric cell division (ACD), which is necessary for plant survival1–4. In Arabidopsis thaliana, the GLYCOGEN SYNTHASE KINASE3 (GSK3)/SHAGGY-like kinase BRASSINOSTEROID INSENSITIVE 2 (BIN2) phosphorylates both the mitogen-activated protein kinase (MAPK) signalling module5,6 and its downstream target, the transcription factor SPEECHLESS (SPCH)7, to promote and restrict ACDs, respectively, in the same stomatal lineage cell. However, the mechanisms that balance these mutually exclusive activities remain unclear. Here we identify the plant-specific protein POLAR as a stomatal lineage scaffold for a subset of GSK3-like kinases that confines them to the cytosol and subsequently transiently polarizes them within the cell, together with BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE (BASL), before ACD. As a result, MAPK signalling is attenuated, enabling SPCH to drive ACD in the nucleus. Moreover, POLAR turnover requires phosphorylation on specific residues, mediated by GSK3. Our study reveals a mechanism by which the scaffolding protein POLAR ensures GSK3 substrate specificity, and could serve as a paradigm for understanding regulation of GSK3 in plants.POLAR, identified in a survey of the protein interactome of BRASSINOSTEROID INSENSITIVE 2 in Arabidopsis thaliana, has a key role in coordinating cell polarity and enabling asymmetric cell division.
Zhenya P. Yordanova, Maria A. Rogova, Miroslava K. Zhiponova, Milen I. Georgiev, and Veneta M. Kapchina-Toteva
Elsevier BV
Abstract Ex situ conservation of Bulgarian endemic plant Achillea thracica Velen. was achieved by successful in vitro cultivation of mono-nodal segments on MS-B5 medium supplemented with 1.0 mg/L BA for 20 days and subsequent transferring of regenerated plants on hormone free basal MS-B5 medium for root development and accumulation of leaf biomass. In vitro multiplicated plants were successfully acclimated in a growth chamber with 100% survival. GC–MS analysis of the essential oils resulted in the identification of 30, 10 and 28 compounds in in situ grown, in vitro cultivated and ex vitro adapted plants, respectively, constituting 77.7%, 99.9% and 84.1% of the total oils. The wider variety of compounds was found in the essential oils of in situ and ex vitro adapted plants where santolina alcohol, β-eudesmol, 1,8-cineole, germacrene D, α-cadinol and artemisia alcohol were the principal components comprising 68.7% and 69.3 of the oil, respectively. In vitro cultivated plants consist of mainly 1,8-cineole, germacrene D and artemisia alcohol representing 87% of the oil. Different growth conditions affect the composition of essential oils, suggesting their possible involvement in the process of adaptation and surviving in changing environmental conditions.
V. Kapchina-Toteva, M.A. Dimitrova, M. Stefanova, D. Koleva, K. Kostov, Zh.P. Yordanova, D. Stefanov, and M.K. Zhiponova
Elsevier BV
The white dead nettle, Lamium album L., is an herb that has been successfully cultivated under in vitro conditions. The L. album micropropagation system offers a combination of factors (light intensity, temperature, carbon dioxide (CO2) level, humidity) that are limiting for plant growth and bioactive capacity. To get a better understanding of the mechanism of plant acclimation towards environmental changes, we performed a comparative investigation on primary and secondary metabolism in fully expanded L. album leaves during the consecutive growth in in situ, in vitro, and ex vitro conditions. Although the genetic identity was not affected, structural and physiological deviations were observed, and the level of bioactive compounds was modified. During in vitro cultivation, the L. album leaves became thinner with unaffected overall leaf organization, but with a reduced number of palisade mesophyll layers. Structural deviation of the thylakoid membrane system was detected. In addition, the photosystem 2 (PS2) electron transport was retarded, and the plants were more vulnerable to light damage as indicated by the decreased photoprotection ability estimated by fluorescence parameters. The related CO2 assimilation and transpiration rates were subsequently reduced, as were the content of essential oils and phenolics. Transfer of the plants ex vitro did not increase the number of palisade numbers, but the chloroplast structure and PS2 functionality were recovered. Strikingly, the rates of CO2 assimilation and transpiration were increased compared to in situ control plants. While the phenolics content reached normal levels during ex vitro growth, the essential oils remained low. Overall, our study broadens the understanding about the nature of plant responses towards environmental conditions.
M. K. Zhiponova, K. Morohashi, I. Vanhoutte, K. Machemer-Noonan, M. Revalska, M. Van Montagu, E. Grotewold, and E. Russinova
Proceedings of the National Academy of Sciences
Significance Our work provides an insight into the complex network of basic helix–loop–helix (bHLH)/helix–loop–helix (HLH) transcription factors that regulates cell elongation. An unknown network motif (an incoherent feed-forward loop) has been discovered that was established by two negative regulators of brassinosteroid responses, namely the HLH transcription factor INCREASED LEAF INCLINATION1 BINDING bHLH1 (IBH1) and its unidentified homolog, IBH1-LIKE1 (IBL1). We also suggest that IBH1 and IBL1 coexist with PHYTOCHROME-INTERACTING FACTOR 4 (another key regulator of cell elongation) in transcriptional complexes. Cell elongation is promoted by different environmental and hormonal signals, involving light, temperature, brassinosteroid (BR), and gibberellin, that inhibit the atypical basic helix–loop–helix (bHLH) transcription factor INCREASED LEAF INCLINATION1 BINDING bHLH1 (IBH1). Ectopic accumulation of IBH1 causes a severe dwarf phenotype, but the cell elongation suppression mechanism is still not well understood. Here, we identified a close homolog of IBH1, IBH1-LIKE1 (IBL1), that also antagonized BR responses and cell elongation. Genome-wide expression analyses showed that IBH1 and IBL1 act interdependently downstream of the BRASSINAZOLE-RESISTANT1 (BZR1)–PHYTOCHROME-INTERACTING FACTOR 4 (PIF4)–DELLA module. Although characterized as non-DNA binding, IBH1 repressed direct IBL1 transcription, and they both acted in tandem to suppress the expression of a common downstream helix–loop–helix (HLH)/bHLH network, thus forming an incoherent feed-forward loop. IBH1 and IBL1 together repressed the expression of PIF4, known to stimulate skotomorphogenesis synergistically with BZR1. Strikingly, PIF4 bound all direct and down-regulated HLH/bHLH targets of IBH1 and IBL1. Additional genome-wide comparisons suggested a model in which IBH1 antagonized PIF4 but not the PIF4–BZR1 dimer.
Zhenya P. Yordanova, Miroslava K. Zhiponova, Elena T. Iakimova, Milena A. Dimitrova, and Veneta M. Kapchina-Toteva
Springer Science and Business Media LLC
Lamium album, commonly known as white dead nettle or non-stinging nettle is a flowering herbaceous plant, native throughout Europe, Western Asia and North Africa. From ancient times this plant has been endowed with revival, curative and culinary virtues. In the past, in the traditional and folk medicine white dead nettle has been used mainly for its anti-inflammatory, astringent and anti-septic activity. Nowadays significant amount of knowledge on the efficacy of extracts and raw material of L. album is accumulated and a number of health-related beneficial activities have been scientifically proven. In vitro analyses conducted in various model systems have demonstrated antiviral, antimicrobial, antioxidant, anticancer, cytoprotective, wound healing and other important pharmacological effects. The present review summarizes the recent information on the phytochemical features of this pharmacologically important species. The findings on the chemical composition, biological activities and the pharmacological properties underlying the revival secret of white dead nettle are described and discussed in the view of potential applications for treatment of human diseases. Trends for further research are outlined.
S. Krumova, M. Zhiponova, K. Dankov, V. Velikova, K. Balashev, T. Andreeva, E. Russinova, and S. Taneva
Elsevier BV
Brassinosteroids (BRs) are plant steroid hormones known to positively affect photosynthesis. In this work we investigated the architecture and function of photosynthetic membranes in mature Arabidopsis rosettes of BR gain-of-function (overexpressing the BR receptor BR INSENSITIVE 1 (BRI1), BRI1OE) and loss-of-function (bri1-116 with inactive BRI1 receptor, and constitutive photomorphogenesis and dwarfism (cpd) deficient in BR biosynthesis) mutants. Data from atomic force microscopy, circular dichroism, fluorescence spectroscopy and polarographic determination of oxygen yields revealed major structural (enlarged thylakoids, smaller photosystem II supercomplexes) and functional (strongly inhibited oxygen evolution, reduced photosystem II quantum yield) changes in all the mutants with altered BR response compared to the wild type plants. The recorded thermal dependences showed severe thermal instability of the oxygen yields in the BR mutant plants. Our results suggest that an optimal BR level is required for the normal thylakoid structure and function.
Miroslava K. Zhiponova, Isabelle Vanhoutte, Véronique Boudolf, Camilla Betti, Stijn Dhondt, Frederik Coppens, Evelien Mylle, Sara Maes, Mary-Paz González-García, Ana I. Caño-Delgado,et al.
Wiley
Brassinosteroid (BR) hormones control plant growth through acting on both cell expansion and division. Here, we examined the role of BRs in leaf growth using the Arabidopsis BR-deficient mutant constitutive photomorphogenesis and dwarfism (cpd). We show that the reduced size of cpd leaf blades is a result of a decrease in cell size and number, as well as in venation length and complexity. Kinematic growth analysis and tissue-specific marker gene expression revealed that the leaf phenotype of cpd is associated with a prolonged cell division phase and delayed differentiation. cpd-leaf-rescue experiments and leaf growth analysis of BR biosynthesis and signaling gain-of-function mutants showed that BR production and BR receptor-dependent signaling differentially control the balance between cell division and expansion in the leaf. Investigation of cell cycle markers in leaves of cpd revealed the accumulation of mitotic proteins independent of transcription. This correlated with an increase in cyclin-dependent kinase activity, suggesting a role for BRs in control of mitosis.
D. Stoyanova-Koleva, M. Stefanova, M. Zhiponova, and V. Kapchina-Toteva
Institute of Experimental Botany
The leaf structure and chloroplast ultrastructure of kidney tea (Orthosiphon stamineus Benth.) was studied in in vitro culture on standard MS medium supplemented with or without plant growth regulators (PGRs). The cytokinin N6-benzyladenine (BA) negatively affected the structure of the palisade parenchyma and chloroplast ultrastructure and increased the stomatal frequency of the adaxial epidermis. The auxin indole-3-butyric acid (IBA) did not modify the morphology of regenerated leaf tissues as well as the chloroplast ultrastructure. The effect of both PGRs applied in combination was manifested in well-differentiated mesophyll parenchyma, typical chloroplast ultrastructure and increased stomatal frequency on both leaf surfaces. This protocol can be suggested for further ex vitro propagation.
Gustavo E. Gudesblat, Joanna Schneider-Pizoń, Camilla Betti, Juliane Mayerhofer, Isabelle Vanhoutte, Walter van Dongen, Sjef Boeren, Miroslava Zhiponova, Sacco de Vries, Claudia Jonak,et al.
Springer Science and Business Media LLC
Stomatal formation is regulated by multiple developmental and environmental signals, but how these signals are integrated to control this process is not fully understood. In Arabidopsis thaliana, the basic helix-loop-helix transcription factor SPEECHLESS (SPCH) regulates the entry, amplifying and spacing divisions that occur during stomatal lineage development. SPCH activity is negatively regulated by mitogen-activated protein kinase (MAPK)-mediated phosphorylation. Here, we show that in addition to MAPKs, SPCH activity is also modulated by brassinosteroid (BR) signalling. The GSK3/SHAGGY-like kinase BIN2 (BR INSENSITIVE2) phosphorylates residues overlapping those targeted by the MAPKs, as well as four residues in the amino-terminal region of the protein outside the MAPK target domain. These phosphorylation events antagonize SPCH activity and limit epidermal cell proliferation. Conversely, inhibition of BIN2 activity in vivo stabilizes SPCH and triggers excessive stomatal and non-stomatal cell formation. We demonstrate that through phosphorylation inputs from both MAPKs and BIN2, SPCH serves as an integration node for stomata and BR signalling pathways to control stomatal development in Arabidopsis.