Auxin, indole-3-acetic acid (IAA), is a key phytohormone with diverse morphogenic roles in land plants, but its function and transport mechanisms in algae remain poorly understood. We therefore aimed to explore the role of IAA in a complex, streptophyte algae Chara braunii. Here, we described novel responses of C. braunii to IAA and characterized two homologs of PIN auxin efflux carriers: CbPINa and CbPINc. We determined their localization in C. braunii using epitope-specific antibodies and tested their function in heterologous land plant models. Further, using phosphoproteomic analysis, we identified IAA-induced phosphorylation events. The thallus regeneration assay showed that IAA promotes thallus elongation and side branch development. Immunolocalization of CbPINa and CbPINc confirmed their presence on the plasma membrane of vegetative and generative cells of C. braunii. However, functional assays in tobacco BY-2 cells demonstrated that CbPINa affects auxin transport, whereas CbPINc does not. The IAA is effective in the acceleration of cytoplasmic streaming and the phosphorylation of evolutionary conserved targets such as homolog of RAF-like kinase. These findings suggest that, although canonical PIN-mediated auxin transport mechanisms might not be fully conserved in Chara, IAA is involved in morphogenesis and fast signaling processes.

• Klíčová slova
• Chara, auxin transport, indole‐3‐acetic acid, plant evolution, streptophytes,
• MeSH
• biologický transport účinky léků   MeSH
• buněčná membrána metabolismus   účinky léků   MeSH
• Chara * metabolismus   účinky léků   MeSH
• fosforylace účinky léků   MeSH
• kyseliny indoloctové * metabolismus   farmakologie   MeSH
• membránové transportní proteiny * metabolismus   MeSH
• rostlinné proteiny * metabolismus   MeSH
• tabák metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• indoleacetic acid MeSH Prohlížeč
• kyseliny indoloctové * MeSH
• membránové transportní proteiny * MeSH
• rostlinné proteiny * MeSH

Melatonin was found in the fresh water characeae Chara australis. The concentrations (~4 μg/g of tissue) were similar in photosynthesizing cells, independent of their position on the plant and rhizoids (roots) without chloroplasts. Exogenous melatonin, added at 10 μM to the artificial pond water, increased quantum yield of photochemistry of photosystem II by 34%. The increased efficiency appears to be due to the amount of open reaction centers of photosystem II, rather than increased efficiency of each reaction center. More open reaction centers reflect better functionality of all photosynthetic transport chain constituents. We suggest that melatonin protection against reactive oxygen species covers not only chlorophyll, but also photosynthetic proteins in general.

• Klíčová slova
• Characeae, antioxidants, chlorophyll fluorescence, melatonin, photosynthesis, reactive oxygen species,
• MeSH
• antioxidancia metabolismus   farmakologie   MeSH
• Chara účinky léků   metabolismus   MeSH
• Characeae MeSH
• chlorofyl metabolismus   MeSH
• chloroplasty MeSH
• fotosyntéza * účinky léků   MeSH
• fotosystém II (proteinový komplex) metabolismus   MeSH
• melatonin metabolismus   farmakologie   MeSH
• reaktivní formy kyslíku metabolismus   MeSH
• světlosběrné proteinové komplexy metabolismus   MeSH
• transport elektronů * účinky léků   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antioxidancia MeSH
• chlorofyl MeSH
• fotosystém II (proteinový komplex) MeSH
• melatonin MeSH
• reaktivní formy kyslíku MeSH
• světlosběrné proteinové komplexy MeSH