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The role of the nascent polypeptide-associated complex (NAC) subunit β in Arabidopsis thaliana response to various abiotic stresses
Šesták, Petr ; Fíla, Jan (advisor) ; Vosolsobě, Stanislav (referee)
Nascent polypeptide-associated complex (NAC) represents a heterodimeric complex composed of an α- and a β-subunit. It is conserved in eukaryotic organisms and has also been found in archaea. This complex binds to newly synthesized proteins emerging from the ribosome and participates in their targeting to the endoplasmic reticulum. In plants, the NAC complex has been studied in the context of tolerance to various abiotic stresses. In our laboratory, we have previously characterized a T-DNA insertion mutant of Arabidopsis thaliana in both NACβ-encoding genes that exhibited a number of phenotypic defects. These included for instance the appearance of more floral organs, reduced pollen grain germination, and the production of shorter siliques with less seeds inside. The aim of this diploma thesis was to characterize the role of the NACβ subunit in Arabidopsis thaliana during seed germination under osmotic and salt stress. We have shown that the absence of NACβ leads to a reduced seed germination and a prolonged germination time, as does overexpression of this subunit. We further studied whether stress conditions affect the transcript levels of individual genes encoding for both NAC subunits by RT-qPCR. In order to investigate the molecular mechanisms by which the studied complex could influence the...
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Studying dimer formation and effectors of Arabidopsis thaliana nascent polypeptide-associated complex
Klodová, Božena ; Fíla, Jan (advisor) ; Robert Boisivon, Helene (referee)
The development of plant flowers represents a complex process controlled by numerous mechanisms. The creation of double homozygous mutant of both β subunits (sometimes also referred to as basic transcription factor 3) of nascent polypeptide associated complex in Arabidopsis thaliana (further referred to as nacβ1 nacβ2) caused quite a strong defective phenotype including abnormal number of flower organs, shorter siliques with a reduced seed set, and inferior pollen germination rate together with a lower ovule targeting efficiency. Previously, NAC complex was described to be formed as a heterodimer composed of an α- and β-subunit, which binds ribosome and acts as a chaperone in Saccharomyces cerevisiae. In plants, NACβ is connected to stress tolerance and to plant development as a transcription regulator. However, little is known of NAC heterodimer function in plants. In this thesis, yeast two hybrid system (Y2H) and bimolecular fluorescence complementation (BiFC) assays were used to verify the NAC heterodimer formation in A. thaliana and to establish any potential interaction preferences between both NACβ paralogues and five NACα paralogues. To deepen the understanding about molecular mechanisms behind the nacβ1 nacβ2 phenotype, flower bud transcriptome of the nacβ1 nacβ2 double homozygous mutants...
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