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Actin nucleation in plant cell
Schiebertová, Petra ; Schwarzerová, Kateřina (advisor) ; Cvrčková, Fatima (referee)
The ability of plant cells to nucleate actin is important especially for dynamic of intracellular movements of organelles and vesicles, cell structure and growth organization and coordination of endo- and exocytosis . Actin nucleation means the development of new actin filaments from G-actin. Actin associated proteins - Arp2/3 complex and formins serve for this purpose. Arp2/3 complex polymerizes new "daughter " filament from the side of the "parent" filament at an angle of 70 degrees and after the nucleation remains at minus end of filaments, thus inducing branching of filaments. Nucleation by Arp2/3 complex further requires nucleation promoting factors - NPFs. Deletion of subunits of Arp2/3 complex is often lethal in animal cells. On the other hand, deletion results in rather mild phenotype in plants. Formins catalyze the formation of direct actin fibers and remain on the plus end of the fiber after nucleation. There are multiple isoforms of formins in plants than in animals, which suggest an important role of formins in plants. New actin nucleators Cobl, Lmod, Spire, JMY and APC containing WH2 (WASP homology 2) domain were identified in non-plant cells. This type of actin nucleation was not described in plants. Kew words: Actin, Arp2/3 complex, formins, Scar/WAVE, Cobl, Lmod, Spire
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Genetically modified plants in practical applications
Říhová, Barbora ; Fischer, Lukáš (advisor) ; Cvrčková, Fatima (referee)
Genetic engineering (GI) of plants is a very current topic, and more and more controversial, since it is becoming an inseparable part of our lives. GI has, among other things, a great potential to help solve the current problem of hunger and malnutrition in certain parts of the world. The goal of this project is to clarify what genetically modified (GM) plants are, to present the possibilities of their practical use, to explain methods of preparation and to consider their advantages and eventual risks. By GM plant we understand a plant whose genetic information has been changed by introducing or removing part of the genetic information (a section of DNA, generally a gene). The most frequently used methods of transformation are the transformation by Agrobacterium tumefaciens and the balistic method. GM plants can be used for production of food or feed in better quality and greater quantity, thanks to an introduction of higher resistance, whether it is to biotic stress (pest, virus or bacterial resistance) or to abiotic stress (drought, salinity, toxic substance in the ground..). In particular, the resistance to abiotic stress is an important issue these days, since through the climate changes some regions suffer more and more from insufficient precipitation and consequent drought. Some of the GM plants grown...
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Functional studies of selected members of the Arabidopsis formin family
Oulehlová, Denisa ; Cvrčková, Fatima (advisor) ; Binarová, Pavla (referee) ; Černý, Jan (referee)
Formins are multidomain proteins containing a conserved formin-homology 2 (FH2) domain, which catalyzes de novo nucleation of actin filaments. In yeast and animal cells, both mechanisms and regulation of formin function have been extensively studied, yet much less is known about action of plant formins, which considerably differ from yeast and animal ones in the domain composition. In higher plants, formins are classified into two groups, Class I and Class II, and so far, experimental data are available only for the first group members. Here I present results of experimental study of several members of the large formin family in Arabidopsis, including the characterization of a Class II formin AtFH16. Arabidopsis genome contains 21 formin-encoding genes, and though they greatly differ in their expression levels and pattern, all of them are transcriptionally active. We selected 17 homozygous T-DNA insertional mutants in 14 formin genes. Under standard cultivation conditions, no obvious phenotypic discrepancies between wild type and mutant plants were found. To impair two dominant pollen formins, an atfh3atfh5 double-mutant was prepared and even in this case, both microspore development and pollen tube growth remained unaffected. Consistently, polarized growth of tobacco pollen tubes was not altered...
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Characterization of membrane protein DREPP
Vosolsobě, Stanislav ; Schwarzerová, Kateřina (advisor) ; Cvrčková, Fatima (referee)
Proteins of DREPP family (20-25 kDa, syn. PCaP1 in Arabidopsis thaliana) first appeared in ferns and we have shown that several independent duplications of DREPP protein occurred during evolution of large families (Poaceae, Brassicaceae, Solanaceae and Asteraceae) and in group Coniferophyta. Secondary losses of one paralogue occurred in subfamilies Pooideae and Solanoideae.We have also detected two large-scale modification of DREEP protein in Asparagales and Brassicaceae (this divergent paralogue was previously described as MAP18 protein). We have examined colinearity of chromosome fragments in vicinity both PCaP1 and MAP18 paralogues in Arabidopsis thaliana and we hypothesize that MAP18 gene arose during genome duplication on the origin of Brassicaceae family. DREPP protein was previously identified in detergent-resistant membrane microdomain fraction and a myristyl anchor was shown to be necessary for their membrane localization. Membrane association was shown to be modified by the interaction of unique N-terminal domain with PtdInsPs, which was inhibited by binding of Ca-calmodulin (Nagasaki et al., 2008). The mutation of Gly2 by Ala in the myristilation site, or C-terminal GFP-fusion (GFP-DREPP), affect membrane association in Arabidopsis thaliana (Nagasaki et al., 2008). Several DREPP paralogues in...
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Serratia marcescens bacterial colony differentiation
Schmoranz, Michal ; Neubauer, Zdeněk (advisor) ; Cvrčková, Fatima (referee)
We explain the typical shape and appearance of bacterial monocolonies grown on rich medias as an active effort of cooperating individuals. This puts each colony into the light of biological aesthetics and shows it as a unique piece of art. We understand the appearance of colonies as a manifestation of the most general dimension of Life, enabled by domestification and relaxing of the stress of natural selection. That is, what allows the colonies to experiment in their morfogeny and to resign on the functional morfogenesis. When kept in convenient conditions, aerobic bacteria tend to build complex colonies with strain specific patterns. The colonies are suprisingly well organised considering that they are built by more than 10 000 times smaller primitive unicellular organisms. In microbiology the colour and shape pattern of the colonies used to be called "the secondary metabolism". Nowadays we consider them to be an effect of the efficient microbial communication and we know, that bacteria have utilized for communication hundreds of different biochemical messages. However, we still do not understand the relevance or the aim of the formation of the colonies and their pattern. Moreover, we are also able to detect a complicated intercolonial behaviour including in some cases cooperation, agressiveness...
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The role of actin dynamics in auxin transport
Stillerová, Lenka ; Cvrčková, Fatima (advisor) ; Schwarzerová, Kateřina (referee)
Phytohormones are signalling molecules directing physiological and developmental processes in plants. One of them, auxin, is involved in the diverse regulation of plant processes, e.g. embryogenesis, organogenesis, vascular tissue formation and tropisms. Auxin transport is polar. Auxin isdistributed via the phloem, utilizing specialized membrane transport proteins; small amount diffuse also through the membrane. Aux1/Lax transporters mediate auxin entry into the cell, auxin efflux is mediate mostly by PIN transporters, which are the crucial factors in determining the directionality of auxin flow. Asymmetric localization of membrane PIN proteins depends on vesicle transport from Golgi to the plasma membrane. Vesicles are transported along actin filaments which are dynamically rebuilted by regulators. They are maintaining asymmetric cellular localization of the auxin transport proteins. PIN proteins are cycling between endosomes and plasma membrane. Cycling is regulated by ARF-GEF proteins and serin/threonin kinase (PID, PINOID). Newly synthesized PIN proteins are equally distributed in the plasma membrane, afterwards they are asymmetrically redistributed. Regulation of actin filaments formation and remodelling is the crucial factor for transport of vesicles with PIN proteins. Many proteins which regulate...
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Transformation of potato with S. pombe mitotic activator cdc25
Ševčíková, Hana ; Lipavská, Helena (advisor) ; Cvrčková, Fatima (referee)
Tuberization is an important process in potato that is governed by a complex of environmental as well as internal factors. As a morphogenic process, it is closely connected with regulation of frequency and orientation of cell division. Thus, the aim of this thesis was to transform potato with mitotic activator cdc25 from Schizosaccharomyces pombe (Spcdc25) and to follow the resulting changes in potato phenotype with a special focus on tuber formation. In previous studies with tobacco, it has been shown that the expression of the above mentioned Spcdc25 gene results in dramatic changes in morphology (leaf structure, restricted root development and growth, and also remarkable developmental change - acceleration of flowering). Moreover, many other characteristics that can be induced in control by cytokinin application have been observed (e.g. cytokinin independent de novo shoot formation, carbohydrate metabolism changes). The two last characteristics - cytokinins independency of morphogenic process and changes in carbohydrate metabolism (e.g. increased starch deposition) - are important from the point of view of expected changes in characteristic of Spcdc25 transgenic potato. To transform potato, the preparation of a plasmid carrying construct with suitable selectable marker was necessary. From original...
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