The role of auxin in streptophyte algae

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..