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Unraveling the Enigmatic World of Auxin Signalling: Subcellular and Tissue- Specific Aspects in the Root of Arabidopsis thaliana
Dubey, Shiv Mani ; Fendrych, Matyáš (advisor) ; Robert Boisivon, Helene (referee) ; Kulich, Ivan (referee)
In this dissertation, my main focus was to advance our understanding of how the plant hormone auxin regulates root growth at the sub-cellular and tissue levels in Arabidopsis thaliana. Auxin controls gene transcription through the SCFTIR1/AFB - Aux/IAA coreceptor complex. Among the TIR1/AFBs auxin receptor family members, TIR1 is strictly localized in the nucleus, while AFB1 is particularly abundant in the cytoplasm but also present in the nucleus. I confirmed the dominant role of AFB1 in controlling rapid auxin responses, such as calcium ion influx, apoplastic alkalinization and rapid root growth inhibition; processes associated with root gravitropism. I discovered a novel AFB1-dependent cytoplasmic auxin perception, and I identified the N-terminal domains of AFB1 and TIR1 crucial in determining their subcellular localization. Furthermore, my research contributed to the discovery that the root surface pH gradient on the root's longitudinal axis is not only regulated by AHA H+ -ATPases, but instead, the rapid auxin response module, comprising the AUX1 auxin influx carrier, AFB1, and the CNCG14 calcium channel, controls the apoplastic pH in the root transition zone. Further, I participated in the discovery of a deeply evolutionarily conserved rapid auxin response pathway that involves the RAF-like kinase,...
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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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