Structural insights into auxin influx mediated by the Arabidopsis AUX1

Zhisen Yang; Hong Wei; Yulin Gan; Huihui Liu; Yang Cao; Huihui An; Xiuzheng Que; Yongxiang Gao; Lizhe Zhu; Shutang Tan; Xin Liu; Linfeng Sun

doi:10.1016/j.cell.2025.04.028

Structural insights into auxin influx mediated by the Arabidopsis AUX1

Cell. 2025 Jul 24;188(15):3960-3973.e15. doi: 10.1016/j.cell.2025.04.028. Epub 2025 May 15.

Authors

Zhisen Yang¹, Hong Wei¹, Yulin Gan¹, Huihui Liu², Yang Cao¹, Huihui An¹, Xiuzheng Que¹, Yongxiang Gao¹, Lizhe Zhu², Shutang Tan³, Xin Liu⁴, Linfeng Sun⁵

Affiliations

¹ Department of Neurology of The First Affiliated Hospital of USTC, MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Hefei National Research Center for Physical Sciences at the Microscale, Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China.
² Warshel Institute for Computational Biology, School of Medicine, The Chinese University of Hong Kong, Shenzhen 518172, China.
³ Department of Neurology of The First Affiliated Hospital of USTC, MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Hefei National Research Center for Physical Sciences at the Microscale, Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China; Biomedical Sciences and Health Laboratory of Anhui Province, University of Science and Technology of China, Hefei 230027, China. Electronic address: sttan@ustc.edu.cn.
⁴ Department of Neurology of The First Affiliated Hospital of USTC, MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Hefei National Research Center for Physical Sciences at the Microscale, Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China; Biomedical Sciences and Health Laboratory of Anhui Province, University of Science and Technology of China, Hefei 230027, China. Electronic address: lx023@ustc.edu.cn.
⁵ Department of Neurology of The First Affiliated Hospital of USTC, MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Hefei National Research Center for Physical Sciences at the Microscale, Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China; Biomedical Sciences and Health Laboratory of Anhui Province, University of Science and Technology of China, Hefei 230027, China. Electronic address: sunlf17@ustc.edu.cn.

PMID: 40378849
DOI: 10.1016/j.cell.2025.04.028

Abstract

Auxin is crucial in orchestrating diverse aspects of plant growth and development and modulating responses to environmental signals. The asymmetric spatiotemporal distribution of auxin generates local gradient patterns, which are regulated by both cellular auxin influx and efflux. The AUXIN1/LIKE-AUX1 (AUX1/LAX) family transporters have been identified as major auxin influx carriers. Here, we characterize the auxin uptake mediated by AUX1 from Arabidopsis thaliana. Using cryoelectron microscopy (cryo-EM), we determine its structure in three states: the auxin-unbound, the auxin-bound, and the competitive inhibitor, 3-chloro-4-hydroxyphenylacetic acid (CHPAA)-bound state. All structures adopt an inward-facing conformation. In the auxin-bound structure, indole-3-acetic acid (IAA) is coordinated to AUX1 primarily through hydrogen bonds with its carboxyl group. The functional roles of key residues in IAA binding are validated by in vitro and in planta analyses. CHPAA binds to the same site as IAA. These findings advance our understanding of auxin transport in plants.

Keywords: AUX1; CHPAA; IAA; auxin; cryo-EM structure; influx carrier; inhibitor; polar auxin transport; substrate.

MeSH terms

Arabidopsis Proteins* / chemistry
Arabidopsis Proteins* / metabolism
Arabidopsis Proteins* / ultrastructure
Arabidopsis* / metabolism
Biological Transport
Cryoelectron Microscopy
Indoleacetic Acids* / chemistry
Indoleacetic Acids* / metabolism
Models, Molecular
Protein Binding

Substances

Indoleacetic Acids
Arabidopsis Proteins
AUX1 protein, Arabidopsis
indoleacetic acid