Auxin response and PIN‐mediated transport in chlorophyte algae
6 affiliations
- 1Institute of Science and Technology Austria (ISTA) Klosterneuburg 3400 Austria
- 2School of Life Sciences Weihenstephan, Plant Systems Biology Technical University of Munich Freising 85354 Germany
- 3Institute of Experimental Botany Czech Academy of Sciences Prague 165 00 Czech Republic
- 4State Key Laboratory for Crop Stress Resistance and High‐Efficiency Production, College of Life Sciences Northwest A&F University Yangling 712100 China
- 5Institute of Future Agriculture Northwest A&F University Yangling 712100 China
- 6Department of Experimental Plant Biology, Faculty of Science Charles University Prague 128 44 Czech Republic
Abstract
Auxin, primarily indole‐3‐acetic acid (IAA), is a central regulator of growth and development in land plants, but its physiological role in chlorophyte algae remains unclear. Here, we show that exogenous IAA modulates growth in Chlorella sorokiniana, Chlorella variabilis, and Chlamydomonas reinhardtii in a concentration‐dependent manner. Low IAA concentrations promoted growth by accelerating the onset of cell division without affecting cell size, whereas higher concentrations inhibited proliferation. Radiotracer assays showed that all three species take up and release IAA across the plasma membrane through a combination of passive diffusion and energy‐dependent, saturable processes. Competition by excess unlabeled natural and synthetic auxins further supported the presence of carrier‐mediated transport with broad substrate recognition. Phylogenetic analyses identified potential PIN‐like auxin exporters in chlorophytes and other non‐plant eukaryotes, and structural modeling supported conservation of the overall PIN fold and predicted auxin‐binding residues. However, functional assays in Xenopus laevis oocytes, tobacco BY‐2 cultured cells, and Arabidopsis thaliana did not support a role for these proteins in directional auxin export. Instead, non‐plant PIN homologs localized predominantly to the endoplasmic reticulum and showed limited or no transport activity in heterologous systems. Together, these findings indicate that auxin responsiveness and basic cellular auxin transport predate canonical PIN‐mediated directional auxin export, which appears to be a later innovation of the streptophyte lineage.
Related
- ROP GTPases are required for YUC transcription and auxin-mediated root hair growth in Arabidopsis
- Polar auxin transport regulates initial auxin patterning and polar nuclear migration during lateral root initiation
- Eucalyptus grandis Auxin Response Factor 10 (EgrARF10) is associated with the modulation of secondary xylem cell wall chemistry
- Auxin-inducible degron-mediated protein depletion in Diplonema papillatum
- A CRC–MYB chromatin loop controls auxin-mediated nectary growth in Arabidopsis
BibTeX
@article{smoljan2026auxin,
title = {{Auxin response and PIN‐mediated transport in chlorophyte algae}},
author = {Adrijana Smoljan and Sarah Koutnik‐Abele and Dmitrii Vladimirtsev and Petr Klíma and Anita Bírošíková and Yuzhou Zhang and Jack Merrin and Maximilian Schuster and Katarina Kurtović and Ulrich Z. Hammes and Jan Petrášek and Jiří Friml},
journal = {Journal of Integrative Plant Biology},
year = {2026},
month = jun,
doi = {10.1111/jipb.70309},
url = {https://doi.org/10.1111/jipb.70309},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Auxin response and PIN‐mediated transport in chlorophyte algae
AU - Adrijana Smoljan
AU - Sarah Koutnik‐Abele
AU - Dmitrii Vladimirtsev
AU - Petr Klíma
AU - Anita Bírošíková
AU - Yuzhou Zhang
AU - Jack Merrin
AU - Maximilian Schuster
AU - Katarina Kurtović
AU - Ulrich Z. Hammes
AU - Jan Petrášek
AU - Jiří Friml
PY - 2026
DA - 2026/06/10
JO - Journal of Integrative Plant Biology
DO - 10.1111/jipb.70309
UR - https://doi.org/10.1111/jipb.70309
AB - Auxin, primarily indole‐3‐acetic acid (IAA), is a central regulator of growth and development in land plants, but its physiological role in chlorophyte algae remains unclear. Here, we show that exogenous IAA modulates growth in Chlorella sorokiniana, Chlorella variabilis, and Chlamydomonas reinhardtii in a concentration‐dependent manner. Low IAA concentrations promoted growth by accelerating the onset of cell division without affecting cell size, whereas higher concentrations inhibited proliferation. Radiotracer assays showed that all three species take up and release IAA across the plasma membrane through a combination of passive diffusion and energy‐dependent, saturable processes. Competition by excess unlabeled natural and synthetic auxins further supported the presence of carrier‐mediated transport with broad substrate recognition. Phylogenetic analyses identified potential PIN‐like auxin exporters in chlorophytes and other non‐plant eukaryotes, and structural modeling supported conservation of the overall PIN fold and predicted auxin‐binding residues. However, functional assays in Xenopus laevis oocytes, tobacco BY‐2 cultured cells, and Arabidopsis thaliana did not support a role for these proteins in directional auxin export. Instead, non‐plant PIN homologs localized predominantly to the endoplasmic reticulum and showed limited or no transport activity in heterologous systems. Together, these findings indicate that auxin responsiveness and basic cellular auxin transport predate canonical PIN‐mediated directional auxin export, which appears to be a later innovation of the streptophyte lineage.
SN - 1672-9072
SN - 1744-7909
ER -