Structural basis of auxin recognition and transport in plant influx carrier AUX1

Huiwen Chen; Junping Fan; Cheng Chi; Jun Zhao; Di Wu; Xiaoguang Lei; Xing Wang Deng; Daohua Jiang

doi:10.1016/j.molp.2025.06.015

Structural basis of auxin recognition and transport in plant influx carrier AUX1

Mol Plant. 2025 Jun 26:S1674-2052(25)00208-4. doi: 10.1016/j.molp.2025.06.015. Online ahead of print.

Authors

Huiwen Chen¹, Junping Fan², Cheng Chi³, Jun Zhao³, Di Wu⁴, Xiaoguang Lei⁵, Xing Wang Deng⁶, Daohua Jiang⁷

Affiliations

¹ Peking University Institute of Advanced Agricultural Sciences, Shandong Laboratory of Advanced Agricultural Sciences at Weifang, Weifang, Shandong 261000, China; Beijing National Laboratory for Condensed Matter Physics, Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
² Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of the Ministry of Education, College of Chemistry and Molecular Engineering, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China.
³ Peking University Institute of Advanced Agricultural Sciences, Shandong Laboratory of Advanced Agricultural Sciences at Weifang, Weifang, Shandong 261000, China.
⁴ Beijing National Laboratory for Condensed Matter Physics, Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100190, China.
⁵ Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of the Ministry of Education, College of Chemistry and Molecular Engineering, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China. Electronic address: jiangdh@iphy.ac.cn.
⁶ Peking University Institute of Advanced Agricultural Sciences, Shandong Laboratory of Advanced Agricultural Sciences at Weifang, Weifang, Shandong 261000, China. Electronic address: jiangdh@iphy.ac.cn.
⁷ Beijing National Laboratory for Condensed Matter Physics, Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100190, China. Electronic address: jiangdh@iphy.ac.cn.

PMID: 40579814
DOI: 10.1016/j.molp.2025.06.015

Abstract

Auxin regulates many aspects of plant growth and development, featuring polar auxin transport mediated by auxin efflux and influx carriers. AUX1 is the prominent auxin importer that actively takes up natural and synthetic auxins. However, the precise mechanisms by which AUX1 recognizes and transports auxin remain elusive. Here, we describe the cryo-electron microscopy structures of Arabidopsis thaliana AUX1 in apo and auxin-bound forms, revealing the structural basis for auxin recognition. AUX1 assumes the LeuT-like fold in an inward conformation. The auxin analogue 2,4-D is recognized by polar residues in the middle of AUX1. We identify a putative cation site in AUX1, which plays a role in stabilizing the inward-facing conformation. His249 undergoes a large conformational shift, and mutation of it completely abolished transport activity, suggesting a crucial role of His249 in AUX1 gating. Together, this study provides a structural foundation for a deeper comprehension of auxin influx by AUX1-like carriers.

Keywords: 2,4-D; AUX1; Polar auxin transport; auxin recognition; cryo-EM structure; transport mechanism.