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The role of auxin in streptophyte algae
Schmidt, Vojtěch ; Petrášek, Jan (advisor) ; Pleskot, Roman (referee)
The phytohormone auxin is an important morphogen with an essential role in the development of land plants, where mechanisms of its action are well described. However, its role in green algae is poorly understood. Land plants are part of the phylum Streptophyta together with six closely related groups of predominantly freshwater green algae (charophytes). So far, the knowledge about the evolutionary origins of auxin action mechanism is mainly based on genomic information, and much less on experimental findings. In this work, the presence of auxin, its precursor, and catabolism products were shown in representative species of charophytes with varying levels measured compounds both produced endogenously and into the culture media. Thus, we gained a comprehensive insight into the possible strategies of auxin homeostasis across the non-land plant streptophytes. Also, an effect of exogenous auxin on the cell morphology and culture growth of the desmid Closterium was investigated. Image analysis of IAA-treated cells revealed a rather pleiotropic effect on cell morphology. The culture growth was inhibited by IAA. Additionally, IAA induced malformations in cell shape, and the extent of this phenomenon across individual cultures was dependent on the culture growth status. Lastly, we optimized the method of...
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The evolution of auxin metabolism, signalling and transport in the green lineage (Viridiplantae)
Schmidt, Vojtěch ; Petrášek, Jan (advisor) ; Fendrych, Matyáš (referee)
Phytohormone auxin is an essential coordinator of growth and development within land- plants. Mechanisms of auxin action in algae is still poorly understood, given that related research has begun recently. Current progress is derived mainly from available sequence data, which are necessary for analysis of gene homology with higher plants. In this case with the genes related to auxin action mechanisms, e.g. metabolism, signaling and transport. Auxin biosynthesis predated the split of Chlorophyta and Streptophyta, but tighter regulation of auxin levels is the matter of land-plants. First auxin responses were probably non-transcriptional. Transcription-regulating nuclear signaling pathway assembled from more ancient domains, some of them were identified in Charophyta, but whole pathway was complete after colonization of land. Auxin transport out of the cell was one of the original mechanisms of regulating its levels. More sophisticated auxin carrier system was proposed to evolve in Charophyta, where polar auxin transport was identified. Auxin as a signaling molecule was present in primitive algae groups, but its response spectrum dramatically increased after colonization of land. Future research of auxin action evolution needs more model organisms to be established, especially from Charophyta....
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