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Photosynthetic characteristics of potato plants with decreased expression of BEL11 transcription factor
Dybová, Magdaléna ; Mašková, Petra (advisor) ; Fischer, Lukáš (referee)
The potato (Solanum tuberosum) is one of the most important crops in the world. Tubers form during morphogenic process called tuberization, which timing is controlled by a complex regu- latory network involving both environmental conditions and internal factors. For the study of this process, model genotype of subspecies S. t. andigena is mostly used. It requires a short photoperiod. Vast majority of cultivated potatos are of spieces S. t. tuberosum that tuberize even under long-day conditions. Regulation of tuber initiation involves the action of endogenous factors, mainly phytohormones, carbohydrates and specific mobile signals, including BEL transcriptional factors - StBEL5, StBEL11 and StBEL29 - which transcripts are produced in leaves and transported into stolons. StBEL5 stimulates tuberization, whereas StBEL11 and -29 suppress it. The aim of this thesis was to contribute to understanding the role of StBEL11 in the regulation of tuberization by characterization of mutants with decreased StBEL11 levels. A sub- objective was to derive of transgenic lines S. t. andigena with decreased StBEL11 levels using a construct with part of StBEL11 coding region in antisense orientation under 35S CaMV pro- motor. I was able to derive forty two stable transgenic lines, which are prepared for StBEL11...
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Plant responses to combined arsenic and cadmium stress
Burešová, Andrea ; Mašková, Petra (advisor) ; Podlipná, Radka (referee)
Arsenic and cadmium are both non-essential, highly toxic and carcinogenic elements that often occur together in the environment. Given the frequent co-contamination of the environment, it is necessary to investigate both plant strategies for dealing with one metal(loid) and the mechanisms that lead to tolerance or, conversely, sensitivity in the presence of both elements. Simultaneous exposure to multiple toxic elements may lead to extensive plant damage, however it may also result in the increasing engagement and intensity of defence strategies. Contamination of the food chain through crops growing on contaminated soils is a major concern, one that poses a risk to both human and animal lives. The aim of this research field is to reduce accumulation and translocation to aboveground edible parts as much as possible, for example by understanding the mechanisms behind heavy metal accumulation and translocation, or by stabilising toxic elements in the soil, or by cleaning up contaminated soil. One method of clean-up is phytoremediation, which usually utilizes plants with high tolerance to toxic elements, called hyperaccumulators. The knowledge of how defence strategies and mechanisms are affected by the interaction of multiple elements is important for identifying plant species capable of activating...
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Regulation of potato tuber onset: the role of auxin
Myslivcová, Jitka ; Mašková, Petra (advisor) ; Havelková, Lenka (referee)
Potato (Solanum tuberosum) is an essential component of food worldwide. The process of tuber formation is controlled by the interplay of external and internal conditions. Understanding of the molecular basis of tuberization, including the effect of photoperiod, pointed to a key role of mobile signals. Among these morphogenic signals StBEL5 and POTH1 transcripts are involved, which are translated in the stolon and form a heterodimer regulating target genes with TTGAC tandem motifs, further an FT homologue, StSP6A, mobile from leaves to stolons as a protein. BEL5/POTH1 and StP6A signaling pathways seem to overlap. Phytohormones also play an important signaling role, i.a. auxins. During tuber initiation, IAA levels in stolon tissues increase. PIN transporters are likely to be involved in the redistribution of auxin in the stolon, but also LAX and ABCB transporters and components of auxin signaling pathway, Aux/IAAs and ARFs are also involved in the process. Although auxins are proved to play an important role during stolon-to-tuber transition, their exact role in the process is not sufficiently clarified. Auxin signaling is interconnected with BEL5/POTH1 and SP6A-mediated tuber signaling, as its target genes in the stolon include those that encode proteins involved in auxin biosynthesis (YUCCA1),...
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Changes in the contents of anthocyanins and photosynthetic pigments in barley leaves under the effect od climate change factors
Nikodymová, Michaela ; Albrechtová, Jana (advisor) ; Mašková, Petra (referee)
Ongoing climate change and its manifestations have a significant impact on agricultural crops, which are exposed to a wide range of abiotic (drought, high or low temperature, elevated UV radiation) and biotic (pathogens, pests) stress factors that can dangerously affect their growth and yield. One of the very important phenomena of climate change is the increasing concentration of CO2 and other greenhouse gases in the atmosphere. Manifestations of climate change, such as high temperature and drought, interact together with increased CO2 concentration, and these interactions can have serious effects on vegetation. This diploma thesis examines the effect of climate change factors and stress factors on the content of pigments with the importance of plant protection against stress, namely photosynthetic pigments and anthocyanins in barley leaves. The aim of the thesis is to find out whether and what are the differences in the response to these factors in two varieties of barley, differ in their resistance to photooxidative stress. The plants were grown in pots in growth chambers under controlled conditions and in flower beds in adjustable greenhouses with open roofs in the experimental station of plant ecophysiology Domanínek of the Global Change Research Institute of the Czech Academy of Sciences in...
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Modulation of BELL transcription factors balance as a tool for tuberisation strengthening in selected potato cultivars
Zounková, Andrea ; Mašková, Petra (advisor) ; Fischer, Lukáš (referee)
Potato (Solanum tuberosum) is the third most important crop in terms of human consumption. Hence understanding regulatory mechanisms controlling tuber initiation is significant not only from a theoretical but also practical point of view. Tuberization of S. tuberosum is a complex morphogenic process regulated by both, environmental conditions and inner plant status. Environmental conditions regulating the onset of tuberization have been known for a long time, but the molecular basis of tuber initiation has only recently been discovered, in particular using wild subspecies S. tuberosum subsp. andigena. BELL transcription factors are among the important components of the regulatory signalling network. The aim of this study was to modulate balance between the BELL transcription factors that induce and repress tuberization towards strengthening of tuber induction using two cultivars of Solanum tuberosum subsp. tuberosum, cv. Kamýk, resp. cv. Korela. To achieve this, transgenic lines carrying construct containing a part of coding sequence StBEL11, resp. StBEL29 in antisense orientation (AS) under control of constitutive promoters and lines carrying complete sequences of StBEL5 and StPTB6 genes under control of their native promoters were derived. We used the StBEL11 and StBEL29 AS constructs with the aim to...
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Cell cycle regulation in plants: the role of CDK activatory dephosphorylation at entry into mitosis
Mašková, Petra ; Macháčková, Ivana (advisor) ; Havel, Ladislav (referee) ; Vaňková, Radomíra (referee)
t I I I I I I I I I I I I I I Summary of PhD. thesis Cel1 division representsone of fundamentalattributesof all living creatuÍes.Basic molecular mechanisms operating during cell proliferation seem to be evolutionary conservedamongeukaryotes.The cell cycle is dividedin four subsequentphases;themost regulatoryeventsareconcentratedin Gr/S andGzlM checkpoints. The key regulatory proteins, cyclin-dependentkinases (CDKs), govern the progress throughthe whole cell cycle. Their function is strictly dependenton catalytic cyclin subunits.The correspondingcyclin partnerbinding CDK determinesthe time window of the specific CDlVcyclin complex actionin individual cell cycle phase.To becomefully active, the complex requiresfurtherposttranslationalmodificationincluding activatory phosphorylationanddephosphorylationof theCDK on specificaminoacidresidues. Plant cell cycle, besideswell-conservedmechanismscoÍlmonto all eukaryotes,exhibits other specific mechanismsresultingfrom plant survival strategy.The Gr/S transitionis stronglyaffectedby extemalandinternalsignals,mainlyphytohormonesandmetabolites, reflectingthe elementaryconditionssuitablefor accomplishmentof the whole cell cycle. The centralmoleculerespondingto thesesignalsat Gr/S is D cyclin, whoseexpressionis regulatedby cýokinin and sucrose(Riou-Khamlichi et aI.,...
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Mutations in brassinosteroid biosynthetic genes and their effects on plant phenotype
Frimlová, Klára ; Rothová, Olga (advisor) ; Mašková, Petra (referee)
Brassinosteroids are important group of phytohormones, whose presence affects anatomy, morphology and development of plants. They occur in all vegetative and mainly generative organs. Brassinosteroids are biosynthesized via two main paths named early C-6 oxidation pathway and late C- 6 oxidation pathway. Brassinosteroid biosynthesis is catalyzed by enzymes from the group of cytochrome P450. Gene mutations - which affect brassinosteroid biosynthesis - have been studied especially in Arabidopsis thaliana L., Pisum sativum L., Solanum lycopersicum L. and Oryza sativa L. Mutations lead to changes in the composition and amount of brassinosteroids in plants. The reduced content of brassinosteroids is manifested by typical phenotype that includes reduced growth, reduced size of plant organs, and dark green leaves in mutant plants. The mutant phenotype can be reversed by exogenous application of brassinosteroids, which is nevertheless dependent on the concentration of the brassinosteroids used. Higher concentrations of brassinosteroids cause mostly inhibition of root elongation. Keywords: brassinosteroids, biosynthesis, mutant, phenotype
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Regulation of floral initiation in woody perennials
Čermák, Vladimír ; Mašková, Petra (advisor) ; Čermák, Vojtěch (referee)
Floral initiation is an important process for temperate woody perennials that affects the subsequent development of the flower. Although this process is well known in annual plants such as Arabidopsis thaliana, not much research has been done in woody plants. This review summarizes the knowledge about mechanisms of flowering induction in woody perennials, compared to the findings in model plants, especially A. thaliana, including factors involved in the regulation of the flowering process. In particular, FT-like genes and TFL1-like genes, which play an important role in the regulation of flowering induction, are discussed in detail. In temperate woody plants the dormancy period follows the floral induction before the floral development. Periodic regulation of this stage is controlled endogenously and, in addition to other factors, it is affected by expression of DAM genes. The genetic mechanisms regulating endodormancy release in woody perennials are similar to vernalization in herbs. Better understanding of processes such as the floral induction and endodormancy release can help us to develop cultivars with a modified flowering time.
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Pharmacologically active compounds in hops
Pýchová, Kateřina ; Cvrčková, Fatima (advisor) ; Mašková, Petra (referee)
The hop plant (Humulus lupulus) is used not only in brewing but also in phytopharmacology and phytotherapy. Among the isolated or chemically produced substances used for healing are xanthohumol, 8-prenylnaringenine and α and β-bitter acids. Nowadays, a lot of attention is paid to their effect on humans - especially to their anticancer activity. But there is a lack of information about the importance of these substances for the hop plant itself. Most of the plant secondary metabolites originally serve for protection of the plant against pathogens and herbivores. The selected metabolites are not an exception. The purpose of this work was to summarize the published data about the biological importance of selected hop secondary metabolites and the effects they have on other organisms than plants, with an emphasis on humans.
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Nightime transpiration and its importance in C3 and C4 plants
Jansová, Renata ; Lhotáková, Zuzana (advisor) ; Mašková, Petra (referee)
Nocturnal stomatal opening is a phenomenon characteristic for CAM plants due to the primary fixation of CO2. However, quite a few studies describe the non-zero nocturnal stomatal conductivity in a number of plants with C3 and C4 metabolism, which were expected to close the stomata completely during the night. The question is, why this behaviour occurs in plants with C3 and C4 metabolism when their photosynthesis does not occur at night and the need for plant cooling is reduced or absent. The aim of this Thesis is to summarize the current knowledge about night-time transpiration of C3 and C4 plants and discuss available hypotheses about the importance and function of the night-time transpiration. The first part of the Thesis summarizes the possible physiological functions of nocturnal stomatal opening. The second part is focused on a more detailed description of selected hypotheses of increase in nutrient uptake, drought response and photosynthesis priming. The last part introduces important factors that may contribute to the regulation of nocturnal transpiration and stomatal conductivity. Although the possible importance of night-time transpiration is intensely discussed, comprehensive research on the function of the nightime transpiration is not yet available. However, a review of available...
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