Institute of Ornamental Plants

Sofia, Bulgaria

Institute of Ornamental Plants

Sofia, Bulgaria
Time filter
Source Type

Iakimova E.T.,Institute of Ornamental Plants | Woltering E.J.,Wageningen University
Planta | Year: 2017

Main conclusion: Physiological and molecular studies support the view that xylogenesis can largely be determined as a specific form of vacuolar programmed cell death (PCD). The studies in xylogenic zinnia cell culture have led to many breakthroughs in xylogenesis research and provided a background for investigations in other experimental models in vitro andin planta. This review discusses the most essential earlier and recent findings on the regulation of xylem elements differentiation and PCD in zinnia and other xylogenic systems.Xylogenesis (the formation of water conducting vascular tissue) is a paradigm of plant developmental PCD. The xylem vessels are composed of fused tracheary elements (TEs)—dead, hollow cells with patterned lignified secondary cell walls. They result from the differentiation of the procambium and cambium cells and undergo cell death to become functional post-mortem. The TE differentiation proceeds through a well-coordinated sequence of events in which differentiation and the programmed cellular demise are intimately connected. For years a classical experimental model for studies on xylogenesis was the xylogenic zinnia (Zinnia elegans) cell culture derived from leaf mesophyll cells that, upon induction by cytokinin and auxin, transdifferentiate into TEs. This cell system has been proven very efficient for investigations on the regulatory components of xylem differentiation which has led to many discoveries on the mechanisms of xylogenesis. The knowledge gained from this system has potentiated studies in other xylogenic cultures in vitro and in planta. The present review summarises the previous and latest findings on the hormonal and biochemical signalling, metabolic pathways and molecular and gene determinants underlying the regulation of xylem vessels differentiation in zinnia cell culture. Highlighted are breakthroughs achieved through the use of xylogenic systems from other species and newly introduced tools and analytical approaches to study the processes. The mutual dependence between PCD signalling and the differentiation cascade in the program of TE development is discussed. © 2017 The Author(s)

Pencheva A.,University of Forestry | Yovkova M.,Institute of Ornamental Plants
Forestry Ideas | Year: 2016

In this study, the results of recent surveys (during the period between 2012 and 2015) on alien insects infesting ornamental plants in Bulgaria are reported. Fourteen species, associated with urban landscape areas and indoor plants, are discussed. Two of them, Ceroplastes sinensis Del Guercio and Lepidosaphes flava (Signoret), are reported for the first time in Bulgaria. Furthermore, Acizzia jamatonica (Kuwayama), Ceroplastes ceriferus (Fabricius), Pseudaulacaspis pentagona (Targioni Tozzetti) and Cydalima perspectalis (Walker) have been found in new localities. Metcalfa pruinosa Say has widened its host range in Bulgaria. Additional distribution data are also provided about Aulacaspis yasumatsui Takagi and Cacoecimorpha pronubana (Höbner). Details on current status, host plants, zoogeographical origin and probable pathways of introduction into Bulgaria are reported for each species. Morphological and biological remarks are given for C. perspectalis and C. sinensis.

Yovkova M.,Institute of Ornamental Plants | Pencheva A.,University of Forestry | Petrovic-Obradovic O.,University of Belgrade
Acta Zoologica Bulgarica | Year: 2016

Elatobium abietinum is reported for the first time in Bulgaria. The aphid was found in the spring of 2014 in three private properties near Sofia (Bistritsa, Pancharevo and Dragalevtsi) on Norway spruce, Picea abies (L.) H. Karst. and Colorado spruce, Picea pungens Englem. Both Picea species are often used in gardens and landscaping. The damage caused by the aphid leads to the full loss of needles from infested branches. In this paper, a brief description of the morphology of E. abietinum is given, accompanied with data on its distribution and biological characteristics. Previous studies in several countries indicated that the aphid is a hazard for both large-sized spruce trees in landscape situations and small-sized trees in nurseries.

Iakimova E.T.,Institute of Ornamental Plants | Iakimova E.T.,Wageningen University | Sobiczewski P.,Research Institute of Horticulture | Michalczuk L.,Research Institute of Horticulture | And 3 more authors.
Plant Physiology and Biochemistry | Year: 2013

In attached apple leaves, spot-inoculated with Erwinia amylovora, the phenotypic appearance of the hypersensitive response (HR) and the participation of ethylene, reactive oxygen species (ROS) and of vacuolar processing enzyme (VPE) (a plant caspase-1-like protease) were analysed. The HR in both the resistant and susceptible genotypes expressed a similar pattern of distinguishable micro HR lesions that progressed into confined macro HR lesions. The HR symptoms in apple were compared to those in non-host tobacco. The morphology of dead cells (protoplast shrinkage and retraction from cell wall) in apple leaves resembled necrotic programmed cell death (PCD). Lesion formation in both cv. Free Redstar (resistant) and cv. Idared (highly susceptible) was preceded by ROS accumulation and elevation of ethylene levels. Treatment of infected leaves with an inhibitor of ethylene synthesis led to a decrease of ethylene emission and suppression of lesion development in both cultivars. In the resistant but not in the susceptible apple cultivar an early and late increase in VPE gene expression was detected. This suggests that VPE might be an underlying component of the response to E. amylovora in resistant apple cultivars. The findings show that in the studied pathosystem the cell death during the HR proceeds through a signal transduction cascade in which ROS, ethylene and VPE pathways play a role. © 2013 Elsevier Masson SAS.

Iakimova E.T.,Wageningen University | Iakimova E.T.,Institute of Ornamental Plants | Woltering E.J.,Wageningen University
Innovative Food Science and Emerging Technologies | Year: 2015

As a source of bioactive ingredients, lettuce is a preferable component of a healthy diet. In recent years the production of fresh-cut produce has become a fast growing business. However, the shreds are highly sensitive to wound-induced browning and premature senescence that substantially reduces the visual and sensory qualities and shortens the shelf life. To improve the fresh-cut quality, in this work, short pre-storage exposure of shreds from butterhead and iceberg lettuce to nitric oxide (NO) gas was applied. It was found that fumigation with 100 and 200 ppm NO for 1 or 2 h remarkably inhibited the browning of the cut surface and of other injured leaf areas; NO treatment delayed the senescence and substantially prolonged the shelf life upon storage at 4 °C and 12 °C. To obtain information on the physiological processes involved in the wound response, the generation of hydrogen peroxide (H2O2) and the occurrence of cell death were analyzed. The results revealed that the wounding stimulated the accumulation of H2O2 thus generating oxidative stress leading to cell death. A correlation between elevated H2O2 levels, cut surface browning, senescence and storability of the fresh-cuts was established. In comparison to mature leaves, younger leaves expressed a lesser susceptibility to wound-induced browning and the associated oxidative stress. Applied NO strongly inhibited the H2O2 accumulation which may explain its beneficial effects. Industrial relevance We demonstrate that short treatments with NO gas substantially inhibit wound-induced browning and largely improve the storability of fresh-cut lettuce. This offers an option for adopting NO treatments for optimization of the post-processing conditions. Implementation of reported findings into practice will offer innovative technological solutions for improvement of the post-harvest quality of fresh-cut lettuce applicable for the industry, distributors and retailers. Moreover, our findings indicate that the browning disorder is to a large extent dependent on the severity of the wound-induced oxidative stress and cell death occurrence. This discovery opens a possibility for the development of metabolic and morphological markers appropriate for the prediction of the quality and shelf life of fresh-cut lettuce with perspective for expanding the research and introducing the tests toward other perishable leafy vegetables. © 2015 Elsevier Ltd. All rights reserved.

Yordanova Z.P.,Sofia University | Woltering E.J.,Wageningen University | Kapchina-Toteva V.M.,Sofia University | Iakimova E.T.,Wageningen University | Iakimova E.T.,Institute of Ornamental Plants
Annals of Botany | Year: 2013

Background and Aims Under stress-promoting conditions unicellular algae can undergo programmed cell death (PCD) but the mechanisms of algal cellular suicide are still poorly understood. In this work, the involvement of caspase-like proteases, DNA cleavage and the morphological occurrence of cell death in wasp venom mastoparan (MP)-treated Chlamydomonas reinhardtii were studied. Methods Algal cells were exposed to MP and cell death was analysed over time. Specific caspase inhibitors were employed to elucidate the possible role of caspase-like proteases. YVADase activity (presumably a vacuolar processing enzyme) was assayed by using a fluorogenic caspase-1 substrate. DNA breakdown was evaluated by DNA laddering and Comet analysis. Cellular morphology was examined by confocal laser scanning microscopy. Key Results MP-treated C. reinhardtii cells expressed several features of necrosis ( protoplast shrinkage) and vacuolar cell death (lytic vesicles, vacuolization, empty cell-walled corpse-containing remains of digested protoplast) sometimes within one single cell and in different individual cells. Nucleus compaction and DNA fragmentation were detected. YVADase activity was rapidly stimulated in response to MP but the early cell death was not inhibited by caspase inhibitors. At later time points, however, the caspase inhibitors were effective in cell-death suppression. Conditioned medium from MP-treated cells offered protection against MP-induced cell death. Conclusions In C. reinhardtii MP triggered PCD of atypical phenotype comprising features of vacuolar and necrotic cell deaths, reminiscent of the modality of hypersensitive response. It was assumed that depending on the physiological state and sensitivity of the cells to MP, the early cell-death phase might be not mediated by caspase-like enzymes, whereas later cell death may involve caspase-like-dependent proteolysis. The findings substantiate the hypothesis that, depending on the mode of induction and sensitivity of the cells, algal PCD may take different forms and proceed through different pathways. © The Author 2012.

Iakimova E.T.,Wageningen University | Iakimova E.T.,Institute of Ornamental Plants | Michaeli R.,Wageningen University | Woltering E.J.,Wageningen University
Protoplasma | Year: 2013

Phospholipase D (PLD) and its product phosphatidic acid (PA) are incorporated in a complex metabolic network in which the individual PLD isoforms are suggested to regulate specific developmental and stress responses, including plant programmed cell death (PCD). Despite the accumulating knowledge, the mechanisms through which PLD/PA operate during PCD are still poorly understood. In this work, the role of PLDα1 in PCD and the associated caspase-like proteolysis, ethylene and hydrogen peroxide (H2O2) synthesis in tomato suspension cells was studied. Wild-type (WT) and PLDα1-silenced cell lines were exposed to the cell death-inducing chemicals camptothecin (CPT), fumonisin B1 (FB1) and CdSO4. A range of caspase inhibitors effectively suppressed CPT-induced PCD in WT cells, but failed to alleviate cell death in PLDα1-deficient cells. Compared to WT, in CPT-treated PLDα1 mutant cells, reduced cell death and decreased production of H2O2 were observed. Application of ethylene significantly enhanced CPT-induced cell death both in WT and PLDα1 mutants. Treatments with the PA derivative lyso-phosphatidic acid and mastoparan (agonist of PLD/PLC signalling downstream of G proteins) caused severe cell death. Inhibitors, specific to PLD and PLC, remarkably decreased the chemical-induced cell death. Taken together with our previous findings, the results suggest that PLDα1 contributes to caspase-like-dependent cell death possibly communicated through PA, reactive oxygen species and ethylene. The dead cells expressed morphological features of PCD such as protoplast shrinkage and nucleus compaction. The presented findings reveal novel elements of PLD/PA-mediated cell death response and suggest that PLDα1 is an important factor in chemical-induced PCD signal transduction. © 2013 Springer-Verlag Wien.

Twumasi P.,Wageningen University | Twumasi P.,Kwame Nkrumah University Of Science And Technology | Iakimova E.T.,Wageningen University | Iakimova E.T.,Institute of Ornamental Plants | And 6 more authors.
BMC Plant Biology | Year: 2010

Background: The xylem vascular system is composed of fused dead, hollow cells called tracheary elements (TEs) that originate through trans-differentiation of root and shoot cambium cells. TEs undergo autolysis as they differentiate and mature. The final stage of the formation of TEs in plants is the death of the involved cells, a process showing some similarities to programmed cell death (PCD) in animal systems. Plant proteases with functional similarity to proteases involved in mammalian apoptotic cell death (caspases) are suggested as an integral part of the core mechanism of most PCD responses in plants, but participation of plant caspase-like proteases in TE PCD has not yet been documented.Results: Confocal microscopic images revealed the consecutive stages of TE formation in Zinnia cells during trans-differentiation. Application of the caspase inhibitors Z-Asp-CH2-DCB, Ac-YVAD-CMK and Ac-DEVD-CHO affected the kinetics of formation and the dimensions of the TEs resulting in a significant delay of TE formation, production of larger TEs and in elimination of the 'two-wave' pattern of TE production. DNA breakdown and appearance of TUNEL-positive nuclei was observed in xylogenic cultures and this was suppressed in the presence of caspase inhibitors.Conclusions: To the best of our knowledge this is the first report showing that caspase inhibitors can modulate the process of trans-differentiation in Zinnia xylogenic cell cultures. As caspase inhibitors are closely associated with cell death inhibition in a variety of plant systems, this suggests that the altered TE formation results from suppression of PCD. The findings presented here are a first step towards the use of appropriate PCD signalling modulators or related molecular genetic strategies to improve the hydraulic properties of xylem vessels in favour of the quality and shelf life of plants or plant parts. © 2010 Twumasi et al; licensee BioMed Central Ltd.

Sokolov R.S.,Institute of Ornamental Plants | Atanassova B.Y.,Institute of Ornamental Plants | Iakimova E.T.,Institute of Ornamental Plants
Journal of Horticultural Research | Year: 2014

The objective of this study was to assess the regeneration response of in vitro cultured Magno-lia × soulangeana 'Alexandrina' and Magnolia liliiflora 'Nigra' to nutrient medium composition. In the primary culture (initiated from dormant axillary buds) combinations of Murashige and Skoog (MS) basal salts with 6-benzylaminopurine and ?-naphthaleneacetic acid were tested. The primary explants of cv. 'Alexandrina' expressed higher regeneration rate than cv. 'Nigra'. For both species, the regeneration was most strongly potentiated at addition of 0.25 mg·dm-3 of the cytokinin alone. The auxin exerted undesir-able effects. Several basal salts media were applied in proliferation stage and their physiological effects were evaluated in reference to traditionally used MS. At culturing on Chée & Pool C2d Vitis Medium (VM) that is for the first time introduced to magnolia and on MS, M. liliiflora formed more but less elongated shoots than M. soulangeana. However, on VM, substantial increase (25-30%) of the number of axillary shoots and leaves, shoot length and fresh and dry weights over MS was established for both species. This suggested VM as promising composition of nutrients in multiplication stage. Microshoots obtained on MS, VM, Rugini Olive Medium and DKW Juglans Medium were successfully rooted in vitro and subsequently established ex vitro. The findings expand the information on magnolia response to culture conditions and contribute to elaboration of innovative elements of protocols for establishing tissue cultures with high regeneration capacity.

Yordanova Z.P.,Sofia University | Zhiponova M.K.,Sofia University | Iakimova E.T.,Institute of Ornamental Plants | Dimitrova M.A.,Sofia University | Kapchina-Toteva V.M.,Sofia University
Phytochemistry Reviews | Year: 2014

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. © 2014 Springer Science+Business Media.

Loading Institute of Ornamental Plants collaborators
Loading Institute of Ornamental Plants collaborators