| Structural highlights
Function
AUX1_ARATH Carrier protein involved in proton-driven auxin influx. Mediates the formation of auxin gradient from developing leaves (site of auxin biosynthesis) to tips by contributing to the loading of auxin in vascular tissues and facilitating acropetal (base to tip) auxin transport within inner tissues of the root apex, and basipetal (tip to base) auxin transport within outer tissues of the root apex. Unloads auxin from the mature phloem to deliver the hormone to the root meristem via the protophloem cell files. Coordinated subcellular localization of AUX1 is regulated by a brefeldin A-sensitive (BFA) vesicle trafficking process. Involved in lateral root formation, trichoblast polarization and root hair elongation. Required for gravitropism and thigmotropism, especially in roots, by modulating responses to auxin, ethylene and cytokinins such as benzyladenine (BA). Needed for ammonium-mediated root-growth inhibition. Confers sensitivity to the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D, auxin analog), and to polar auxin transport inhibitors such as N-1-naphthylphthalamic acid (NPA) and 2,3,5-triiodobenzoic acid (TIBA).[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21]
Publication Abstract from PubMed
Auxin regulates numerous aspects of plant growth and development, featuring polar auxin transport mediated by auxin efflux and influx carriers. AUX1 is the major auxin importer that actively takes up natural and synthetic auxins. However, the precise mechanisms underlying AUX1-mediated auxin recognition and transport remain elusive. Here, we present cryoelectron microscopy structures of Arabidopsis thaliana AUX1 in both apo and auxin-bound states, revealing the structural basis for auxin recognition. Structural analyses show that AUX1 assumes the LeuT-like fold in an inward-facing conformation and the auxin analog 2,4-D is recognized by polar residues located in the central cavity of AUX1. Furthermore, we identify a putative cation-binding site that contributes to stabilizing the inward-facing conformation. Interestingly, we reveal that His249 undergoes a substantial conformational shift, and its mutation completely abolishes transport activity, suggesting a crucial role for His249 in AUX1 gating. Collectively, this study provides a structural foundation for a deeper understanding of auxin influx by AUX1-like carriers.
Structural basis of auxin recognition and transport by the plant influx carrier AUX1.,Chen H, Fan J, Chi C, Zhao J, Wu D, Lei X, Deng XW, Jiang D Mol Plant. 2025 Aug 4;18(8):1284-1293. doi: 10.1016/j.molp.2025.06.015. Epub 2025 , Jun 26. PMID:40579814[22]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Pitts RJ, Cernac A, Estelle M. Auxin and ethylene promote root hair elongation in Arabidopsis. Plant J. 1998 Dec;16(5):553-60. PMID:10036773 doi:10.1046/j.1365-313x.1998.00321.x
- ↑ Marchant A, Kargul J, May ST, Muller P, Delbarre A, Perrot-Rechenmann C, Bennett MJ. AUX1 regulates root gravitropism in Arabidopsis by facilitating auxin uptake within root apical tissues. EMBO J. 1999 Apr 15;18(8):2066-73. PMID:10205161 doi:10.1093/emboj/18.8.2066
- ↑ Parry G, Delbarre A, Marchant A, Swarup R, Napier R, Perrot-Rechenmann C, Bennett MJ. Novel auxin transport inhibitors phenocopy the auxin influx carrier mutation aux1. Plant J. 2001 Feb;25(4):399-406. PMID:11260496 doi:10.1046/j.1365-313x.2001.00970.x
- ↑ Rahman A, Amakawa T, Goto N, Tsurumi S. Auxin is a positive regulator for ethylene-mediated response in the growth of Arabidopsis roots. Plant Cell Physiol. 2001 Mar;42(3):301-7. PMID:11266581 doi:10.1093/pcp/pce035
- ↑ Timpte C, Lincoln C, Pickett FB, Turner J, Estelle M. The AXR1 and AUX1 genes of Arabidopsis function in separate auxin-response pathways. Plant J. 1995 Oct;8(4):561-9. PMID:11536712 doi:10.1046/j.1365-313x.1995.8040561.x
- ↑ Swarup R, Friml J, Marchant A, Ljung K, Sandberg G, Palme K, Bennett M. Localization of the auxin permease AUX1 suggests two functionally distinct hormone transport pathways operate in the Arabidopsis root apex. Genes Dev. 2001 Oct 15;15(20):2648-53. PMID:11641271 doi:10.1101/gad.210501
- ↑ Grebe M, Friml J, Swarup R, Ljung K, Sandberg G, Terlou M, Palme K, Bennett MJ, Scheres B. Cell polarity signaling in Arabidopsis involves a BFA-sensitive auxin influx pathway. Curr Biol. 2002 Feb 19;12(4):329-34. PMID:11864575 doi:10.1016/s0960-9822(02)00654-1
- ↑ Marchant A, Bhalerao R, Casimiro I, Eklöf J, Casero PJ, Bennett M, Sandberg G. AUX1 promotes lateral root formation by facilitating indole-3-acetic acid distribution between sink and source tissues in the Arabidopsis seedling. Plant Cell. 2002 Mar;14(3):589-97. PMID:11910006 doi:10.1105/tpc.010354
- ↑ Rahman A, Hosokawa S, Oono Y, Amakawa T, Goto N, Tsurumi S. Auxin and ethylene response interactions during Arabidopsis root hair development dissected by auxin influx modulators. Plant Physiol. 2002 Dec;130(4):1908-17. PMID:12481073 doi:10.1104/pp.010546
- ↑ Swarup R, Kargul J, Marchant A, Zadik D, Rahman A, Mills R, Yemm A, May S, Williams L, Millner P, Tsurumi S, Moore I, Napier R, Kerr ID, Bennett MJ. Structure-function analysis of the presumptive Arabidopsis auxin permease AUX1. Plant Cell. 2004 Nov;16(11):3069-83. PMID:15486104 doi:10.1105/tpc.104.024737
- ↑ Pickett FB, Wilson AK, Estelle M. The aux1 Mutation of Arabidopsis Confers Both Auxin and Ethylene Resistance. Plant Physiol. 1990 Nov;94(3):1462-6. PMID:16667854 doi:10.1104/pp.94.3.1462
- ↑ Roman G, Lubarsky B, Kieber JJ, Rothenberg M, Ecker JR. Genetic analysis of ethylene signal transduction in Arabidopsis thaliana: five novel mutant loci integrated into a stress response pathway. Genetics. 1995 Mar;139(3):1393-409. PMID:7768447 doi:10.1093/genetics/139.3.1393
- ↑ Cao Y, Glass AD, Crawford NM. Ammonium inhibition of Arabidopsis root growth can be reversed by potassium and by auxin resistance mutations aux1, axr1, and axr2. Plant Physiol. 1993 Jul;102(3):983-9. PMID:8278539 doi:10.1104/pp.102.3.983
- ↑ Bennett MJ, Marchant A, Green HG, May ST, Ward SP, Millner PA, Walker AR, Schulz B, Feldmann KA. Arabidopsis AUX1 gene: a permease-like regulator of root gravitropism. Science. 1996 Aug 16;273(5277):948-50. PMID:8688077 doi:10.1126/science.273.5277.948
- ↑ Fujita H, Syono K. Genetic analysis of the effects of polar auxin transport inhibitors on root growth in Arabidopsis thaliana. Plant Cell Physiol. 1996 Dec;37(8):1094-101. PMID:9032965 doi:10.1093/oxfordjournals.pcp.a029059
- ↑ Marchant A, Bennett MJ. The Arabidopsis AUX1 gene: a model system to study mRNA processing in plants. Plant Mol Biol. 1998 Feb;36(3):463-71. PMID:9484486 doi:10.1023/a:1005961303167
- ↑ Yamamoto M, Yamamoto KT. Differential effects of 1-naphthaleneacetic acid, indole-3-acetic acid and 2,4-dichlorophenoxyacetic acid on the gravitropic response of roots in an auxin-resistant mutant of arabidopsis, aux1. Plant Cell Physiol. 1998 Jun;39(6):660-4. PMID:9697346 doi:10.1093/oxfordjournals.pcp.a029419
- ↑ Grebe M, Friml J, Swarup R, Ljung K, Sandberg G, Terlou M, Palme K, Bennett MJ, Scheres B. Cell polarity signaling in Arabidopsis involves a BFA-sensitive auxin influx pathway. Curr Biol. 2002 Feb 19;12(4):329-34. PMID:11864575 doi:10.1016/s0960-9822(02)00654-1
- ↑ Fujita H, Syono K. Genetic analysis of the effects of polar auxin transport inhibitors on root growth in Arabidopsis thaliana. Plant Cell Physiol. 1996 Dec;37(8):1094-101. PMID:9032965 doi:10.1093/oxfordjournals.pcp.a029059
- ↑ Parry G, Delbarre A, Marchant A, Swarup R, Napier R, Perrot-Rechenmann C, Bennett MJ. Novel auxin transport inhibitors phenocopy the auxin influx carrier mutation aux1. Plant J. 2001 Feb;25(4):399-406. PMID:11260496 doi:10.1046/j.1365-313x.2001.00970.x
- ↑ Timpte C, Lincoln C, Pickett FB, Turner J, Estelle M. The AXR1 and AUX1 genes of Arabidopsis function in separate auxin-response pathways. Plant J. 1995 Oct;8(4):561-9. PMID:11536712 doi:10.1046/j.1365-313x.1995.8040561.x
- ↑ Chen H, Fan J, Chi C, Zhao J, Wu D, Lei X, Deng XW, Jiang D. Structural basis of auxin recognition and transport by the plant influx carrier AUX1. Mol Plant. 2025 Aug 4;18(8):1284-1293. PMID:40579814 doi:10.1016/j.molp.2025.06.015
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