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 synthet...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.展开更多
Polar auxin transport,which depends on polarized subcellular distribution of AUXIN RESISTANT 1/LIKE AUX1（AUX1/LAX） influx carriers and PIN-FORMED（PIN） efflux carriers,mediates various processes of plant growth and...Polar auxin transport,which depends on polarized subcellular distribution of AUXIN RESISTANT 1/LIKE AUX1（AUX1/LAX） influx carriers and PIN-FORMED（PIN） efflux carriers,mediates various processes of plant growth and development.Endosomal recycling of PIN1 is mediated by an adenosine diphosphate（ADP）ribosylation factor（ARF）-GTPase exchange factor protein,GNOM.However,the mediation of auxin influx carrier recycling is poorly understood.Here,we report that overexpression of OsAGAP,an ARF-GTPase-activating protein in rice,stimulates vesicle transport from the plasma membrane to the Golgi apparatus in protoplasts and transgenic plants and induces the accumulation of early endosomes and AUX1.AUX1 endosomes could partially colocalize with FM4-64 labeled early endosome after actin disruption.Furthermore,OsAGAP is involved in actin cytoskeletal organization,and its overexpression tends to reduce the thickness and bundling of actin filaments.Fluorescence recovery after photobleaching analysis revealed exocytosis of the AUX1 recycling endosome was not affected in the OsAGAP overexpression cells,and was only slightly promoted when the actin filaments were completely disrupted by Lat B.Thus,we propose that AUX1 accumulation in the OsAGAP overexpression and actin disrupted cells may be due to the fact that endocytosis of the auxin influx carrier AUX1 early endosome was greatly promoted by actin cytoskeleton disruption.展开更多
Polar transport of the phytohormone auxin and the establishment of localized auxin maxima regulate em- bryonic development, stem cell maintenance, root and shoot architecture, and tropic growth responses. The past dec...Polar transport of the phytohormone auxin and the establishment of localized auxin maxima regulate em- bryonic development, stem cell maintenance, root and shoot architecture, and tropic growth responses. The past decade has been marked by dramatic progress in efforts to elucidate the complex mechanisms by which auxin transport regulates plant growth. As the understanding of auxin transport regulation has been increasingly elaborated, it has become clear that this process is involved in almost all plant growth and environmental responses in some way. However, we still lack information about some basic aspects of this fundamental regulatory mechanism. In this review, we present what we know （or what we think we know） and what we do not know about seven auxin-regulated processes. We discuss the role of auxin transport in gravitropism in primary and lateral roots, phototropism, shoot branching, leaf expansion, and venation. We also discuss the auxin reflux/fountain model at the root tip, flavonoid modulation of auxin transport processes, and outstanding aspects of post-translational regulation of auxin transporters. This discussion is not meant to be exhaustive, but highlights areas in which generally held assumptions require more substantive validation.展开更多
基金funded by the Shandong Provincial Science and Technology Innovation Fund,the Shandong Provincial Natural Science Foundation(grant no.SYS202206 to J.Z.)the National Key R&D Program of China(grant no.2024YFA1306701 to X.W.D.)+3 种基金the Key Program of the National Natural Science Foundation of China(grant no.32230006 to D.W.,grant nos.32271272 and T2221001 to D.J.,grant nos.22193073,22337002,and 92253305 to X.L.)the Taishan Scholars Program of Shandong Province(to C.C.)the Beijing National Laboratory for Molecular Sciences(grant no.BNLMS-CXX-202106 to X.L.)supported by the New Cornerstone Science Foundation through the XPLORERPRIZE.
文摘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.
基金supported by the Innovative Program of the Chinese Academy of Sciences (KSCX2-YW-N-041)the National Natural Science Foundation of China(30670197)
文摘Polar auxin transport,which depends on polarized subcellular distribution of AUXIN RESISTANT 1/LIKE AUX1（AUX1/LAX） influx carriers and PIN-FORMED（PIN） efflux carriers,mediates various processes of plant growth and development.Endosomal recycling of PIN1 is mediated by an adenosine diphosphate（ADP）ribosylation factor（ARF）-GTPase exchange factor protein,GNOM.However,the mediation of auxin influx carrier recycling is poorly understood.Here,we report that overexpression of OsAGAP,an ARF-GTPase-activating protein in rice,stimulates vesicle transport from the plasma membrane to the Golgi apparatus in protoplasts and transgenic plants and induces the accumulation of early endosomes and AUX1.AUX1 endosomes could partially colocalize with FM4-64 labeled early endosome after actin disruption.Furthermore,OsAGAP is involved in actin cytoskeletal organization,and its overexpression tends to reduce the thickness and bundling of actin filaments.Fluorescence recovery after photobleaching analysis revealed exocytosis of the AUX1 recycling endosome was not affected in the OsAGAP overexpression cells,and was only slightly promoted when the actin filaments were completely disrupted by Lat B.Thus,we propose that AUX1 accumulation in the OsAGAP overexpression and actin disrupted cells may be due to the fact that endocytosis of the auxin influx carrier AUX1 early endosome was greatly promoted by actin cytoskeleton disruption.
基金This work was funded by the National Science Foundation，A.S.M.and Purdue Agriculture Research Foundation grant to W.A.P
文摘Polar transport of the phytohormone auxin and the establishment of localized auxin maxima regulate em- bryonic development, stem cell maintenance, root and shoot architecture, and tropic growth responses. The past decade has been marked by dramatic progress in efforts to elucidate the complex mechanisms by which auxin transport regulates plant growth. As the understanding of auxin transport regulation has been increasingly elaborated, it has become clear that this process is involved in almost all plant growth and environmental responses in some way. However, we still lack information about some basic aspects of this fundamental regulatory mechanism. In this review, we present what we know （or what we think we know） and what we do not know about seven auxin-regulated processes. We discuss the role of auxin transport in gravitropism in primary and lateral roots, phototropism, shoot branching, leaf expansion, and venation. We also discuss the auxin reflux/fountain model at the root tip, flavonoid modulation of auxin transport processes, and outstanding aspects of post-translational regulation of auxin transporters. This discussion is not meant to be exhaustive, but highlights areas in which generally held assumptions require more substantive validation.
