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Published on: April 17, 2016
Auxin response and PIN-mediated transport in chlorophyte algae
Adrijana Smoljan1, Sarah Koutnik-Abele2, Dmitrii Vladimirtsev1
1Institute of Science and Technology Austria (ISTA), Klosterneuburg, 3400, Austria.
Journal of Integrative Plant Biology
|June 11, 2026
Summary
The plant hormone auxin (indole-3-acetic acid) influences algae growth. Basic auxin transport mechanisms evolved before specialized PIN proteins, which are key for directional transport in land plants.
Area of Science:
- Plant biology
- Algal physiology
- Molecular evolution
Background:
- Indole-3-acetic acid (IAA) is a crucial plant hormone regulating growth.
- Its role in chlorophyte algae remains largely unknown.
- Understanding auxin's function in algae provides insights into early plant evolution.
Purpose of the Study:
- To investigate the physiological effects of IAA on chlorophyte algae growth.
- To characterize auxin uptake and transport mechanisms in these algae.
- To explore the evolutionary origins of auxin transport proteins, particularly PIN homologs.
Main Methods:
- Controlled experiments exposing Chlorella and Chlamydomonas to varying IAA concentrations.
- Radiotracer assays to quantify IAA uptake and release.
- Phylogenetic analysis to identify potential auxin transporter genes.
- Heterologous expression systems (Xenopus oocytes, tobacco BY-2 cells, Arabidopsis) to test protein function.
Main Results:
- Exogenous IAA modulated algal growth in a concentration-dependent manner, promoting it at low concentrations and inhibiting it at high concentrations.
- Algae actively transport IAA via both passive diffusion and saturable, energy-dependent carriers.
- Identified PIN-like proteins in chlorophytes showed no evidence of directional auxin export in functional assays.
- These non-plant PIN homologs localized to the endoplasmic reticulum.
Conclusions:
- Auxin responsiveness and fundamental transport mechanisms are ancient, predating land plant evolution.
- Canonical PIN-mediated directional auxin export is a later evolutionary development within the streptophyte lineage.
- The study clarifies auxin's role in algae and sheds light on the evolution of plant hormone signaling and transport.
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