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Cellular processes in twining plants and tendrils
Šimečková, Jana ; Krtková, Jana (advisor) ; Skokan, Roman (referee)
This work focuses on the twining of stems and tendrils of vines and the underlying cellular processes involved. Vines, comprising a diverse group, require support for their growth and are known as "climbers." Successful coiling depends on the contact between the plant and the support, this contact is facilitated by movements such as skototropism and circumnutation. Once in contact with the support, coiling occurs. Specialized G-fiber cells appear to play a crucial role in the coiling process. Additionally, microtubules and cellulose microfibrils are extensively studied in the context of helical growth. Although the complete picture of cellular signaling during coiling remains elusive, numerous chemical substances influencing coiling have been identified, including jasmonates and other plant hormones. Many significant plants fall into the category of climbing plants, yet much remains unknown about their coiling mechanisms.
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Auxin transport in algae
Skokan, Roman ; Petrášek, Jan (advisor) ; Bíšová, Kateřina (referee)
Phytohormone auxin plays an important role in regulating plant development. Directional (polar) cell-to-cell auxin transport creates auxin gradients within plant tissues, which trigger a specific developmental response. The vast majority of available data concerns angiosperms. Lower land plants have been much less explored in this regard, but the important auxin-related mechanisms (including polar auxin transport) are already present in mosses. To uncover the origins of auxin action, one must focus on green algae, especially of clade Streptophyta, which are the direct ancestors of all land plants. In this study, the possible effects of auxins, both native and synthetic, were investigated on two algae: basal, unicellular Chlorella lobophora and advanced, filamentous Spirogyra sp. The latter received comparably more attention, since it belongs to a clade now acknowledged as a sister group to land plants. Chlorella lobophora culture growth was irresponsive to synthetic auxin NAA. The average Spirogyra sp. cell length was, however, changed by auxins at high concentrations. By conducting accumulation assays of radioactively labelled auxins and HPLC analysis, auxin metabolism and transport was investigated in Spirogyra sp. This alga was able to metabolize the plant-native IAA, but not synthetic auxins...
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The evolution of auxin homeostasis mechanisms
Skokan, Roman ; Petrášek, Jan (advisor) ; Buschmann, Henrik (referee) ; Holzinger, Andreas (referee)
The evolution of auxin homeostasis mechanisms Ph.D. thesis Roman Skokan, 2021 Abstract The streptophyte lineage consists of land plants (embryophytes) and several groups of primarily freshwater green algae called charophytes. While the phytohormone auxin is a conserved regulator of land plant development, little has been known of the possible origins of auxin response mechanisms in charophytes. We found that one of these mechanisms, the cellular auxin efflux via the PIN family of transport proteins, is most likely a deeply conserved feature in streptophytes. Additionally, we investigated the state of conservation in the green lineage (Viridiplantae) of the gene families known to be involved in auxin transport in land plants. We revealed that some families are deeply conserved outside land plants, but not others. We also helped uncover a unique radiation within the PIN family in Charophyceae. Striving to uncover the native significance of auxin transport in charophytes, we discovered a growth response to exogenously-applied auxin in Closterium, though the effort to produce stable mutant lines in the native PIN homolog is still underway. Altogether, we brought important insights into the evolution of auxin transport and response in the streptophyte lineage, though many questions still remain.
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Auxin transport in algae
Skokan, Roman ; Petrášek, Jan (advisor) ; Bíšová, Kateřina (referee)
Phytohormone auxin plays an important role in regulating plant development. Directional (polar) cell-to-cell auxin transport creates auxin gradients within plant tissues, which trigger a specific developmental response. The vast majority of available data concerns angiosperms. Lower land plants have been much less explored in this regard, but the important auxin-related mechanisms (including polar auxin transport) are already present in mosses. To uncover the origins of auxin action, one must focus on green algae, especially of clade Streptophyta, which are the direct ancestors of all land plants. In this study, the possible effects of auxins, both native and synthetic, were investigated on two algae: basal, unicellular Chlorella lobophora and advanced, filamentous Spirogyra sp. The latter received comparably more attention, since it belongs to a clade now acknowledged as a sister group to land plants. Chlorella lobophora culture growth was irresponsive to synthetic auxin NAA. The average Spirogyra sp. cell length was, however, changed by auxins at high concentrations. By conducting accumulation assays of radioactively labelled auxins and HPLC analysis, auxin metabolism and transport was investigated in Spirogyra sp. This alga was able to metabolize the plant-native IAA, but not synthetic auxins...
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Evoluce mechanismů transportu auxinu.
Skokan, Roman ; Petrášek, Jan (advisor) ; Cvrčková, Fatima (referee)
Auxin, the longest studied phytohormone, is distinguished from other phytohormones by its unique directional, so-called polar transport. This feature helps to facilitate the broad range of auxin action at all stages of plant development. The polar auxin transport has been evolving together with plant lineages. By studying the mechanisms of auxin transport, biosynthesis, metabolism and particularly signaling we can perhaps better elucidate many milestones of plant evolution, such as complex multicellularity or transition to land. This bachelor thesis summarizes the available data and gives a basic overview of auxin-related characteristics. As far as we know, the advanced mechanisms of auxin transport and signaling known from land plants are probably not very ancient and are absent in various algae. Auxin biosynthesis, however, is rather common and a lot of green algae contain orthologs of important biosynthetic enzymes from land plants. Based on the available data it seems that a complete auxin signalling pathway coupled with proteasomal degradation and affecting gene expression is not present in algae. The polar auxin transport, so far with the earliest evidence from moss sporophytes, was recently found in the gametophytic thallus of stonewort (Chara) from a green algal clade Streptophyta, which is...
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