RESUMO
Biological membranes play a crucial role in actively hosting, modulating and coordinating a wide range of molecular events essential for cellular function. Membranes are organized into diverse domains giving rise to dynamic molecular patchworks. However, the very definition of membrane domains has been the subject of continuous debate. For example, in the plant field, membrane domains are often referred to as nanodomains, nanoclusters, microdomains, lipid rafts, membrane rafts, signalling platforms, foci or liquid-ordered membranes without any clear rationale. In the context of plant-microbe interactions, microdomains have sometimes been used to refer to the large area at the plant-microbe interface. Some of these terms have partially overlapping meanings at best, but they are often used interchangeably in the literature. This situation generates much confusion and limits conceptual progress. There is thus an urgent need for us as a scientific community to resolve these semantic and conceptual controversies by defining an unambiguous nomenclature of membrane domains. In this Review, experts in the field get together to provide explicit definitions of plasma membrane domains in plant systems and experimental guidelines for their study. We propose that plasma membrane domains should not be considered on the basis of their size alone but rather according to the biological system being considered, such as the local membrane environment or the entire cell.
Assuntos
Membrana Celular , Microdomínios da Membrana , Plantas , Terminologia como Assunto , Microdomínios da Membrana/metabolismo , Membrana Celular/metabolismoRESUMO
Plants and algae play a crucial role in the earth's ecosystems. Through photosynthesis they convert light energy into chemical energy, capture CO2 and produce oxygen and energy-rich organic compounds. Photosynthetic organisms are primary producers and synthesize the essential omega 3 and omega 6 fatty acids. They have also unique and highly diverse complex lipids, such as glycolipids, phospholipids, triglycerides, sphingolipids and phytosterols, with nutritional and health benefits. Plant and algal lipids are useful in food, feed, nutraceutical, cosmeceutical and pharmaceutical industries but also for green chemistry and bioenergy. The analysis of plant and algal lipidomes represents a significant challenge due to the intricate and diverse nature of their composition, as well as their plasticity under changing environmental conditions. Optimization of analytical tools is crucial for an in-depth exploration of the lipidome of plants and algae. This review highlights how lipidomics analytical tools can be used to establish a complete mapping of plant and algal lipidomes. Acquiring this knowledge will pave the way for the use of plants and algae as sources of tailored lipids for both industrial and environmental applications. This aligns with the main challenges for society, upholding the natural resources of our planet and respecting their limits.
RESUMO
Sphingolipids are essential membrane components involved in a wide range of cellular, developmental and signaling processes. Sphingolipids are so essential that knock-out mutation often leads to lethality. In recent years, conditional or weak allele mutants as well as the broadening of the pharmacological catalog allowed to decipher sphingolipid function more precisely in a less invasive way. This review intends to provide a discussion and point of view on the function of sphingolipids with a main focus on endomembrane trafficking, Golgi-mediated protein sorting, cell polarity, cell-to-cell communication and cell signaling at the plasma membrane. While our main angle is the plant field research, we will constantly refer to and compare with the advances made in the yeast and animal field. In this review, we will emphasize the role of sphingolipids not only as a membrane component, but also as a key player at a center of homeostatic regulatory networks involving direct or indirect interaction with other lipids, proteins and ion fluxes.
Assuntos
Saccharomyces cerevisiae , Esfingolipídeos , Animais , Esfingolipídeos/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Membrana Celular/metabolismo , Transdução de Sinais , Membranas/metabolismoRESUMO
Anionic phospholipids (PS, PA, PI, PIPs) are low-abundant phospholipids with impactful functions in cell signaling, membrane trafficking and cell differentiation processes. They can be quickly metabolized and can transiently accumulate at defined spots within the cell or an organ to respond to physiological or environmental stimuli. As even a small change in their composition profile will produce a significant effect on biological processes, it is crucial to develop a sensitive and optimized analytical method to accurately detect and quantify them. While thin-layer chromatography (TLC) separation coupled with gas chromatography (GC) detection methods already exist, they do not allow for precise, sensitive, and accurate quantification of all anionic phospholipid species. Here we developed a method based on high-performance liquid chromatography (HPLC) combined with two-dimensional mass spectrometry (MS2 ) by MRM mode to detect and quantify all molecular species and classes of anionic phospholipids in one shot. This method is based on a derivatization step by methylation that greatly enhances the ionization, the separation of each peak, the peak resolution as well as the limit of detection and quantification for each individual molecular species, and more particularly for PA and PS. Our method universally works in various plant samples. Remarkably, we identified that PS is enriched with very long chain fatty acids in the roots but not in aerial organs of Arabidopsis thaliana. Our work thus paves the way for new studies on how the composition of anionic lipids is finely tuned during plant development and environmental responses.
Assuntos
Arabidopsis , Fosfolipídeos , Fosfolipídeos/metabolismo , Cromatografia Líquida/métodos , Espectrometria de Massa com Cromatografia Líquida , Espectrometria de Massas em Tandem/métodos , Cromatografia Líquida de Alta Pressão/métodos , Arabidopsis/metabolismoRESUMO
Extreme environmental conditions eventually limit plant growth [J. R. Dinneny, Annu. Rev. Cell Dev. Biol. 35, 1-19 (2019), N. Gigli-Bisceglia, C. Testerink, Curr. Opin. Plant Biol. 64, 102120 (2021)]. Here, we reveal a mechanism that enables multiple external cues to get integrated into auxin-dependent growth programs in Arabidopsis thaliana. Our forward genetics approach on dark-grown hypocotyls uncovered that an imbalance in membrane lipids enhances the protein abundance of PIN-LIKES (PILS) [E. Barbez et al., Nature 485, 119 (2012)] auxin transport facilitators at the endoplasmic reticulum (ER), which thereby limits nuclear auxin signaling and growth rates. We show that this subcellular response relates to ER stress signaling, which directly impacts PILS protein turnover in a tissue-dependent manner. This mechanism allows PILS proteins to integrate environmental input with phytohormone auxin signaling, contributing to stress-induced growth adaptation in plants.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Ácidos Indolacéticos/metabolismo , Arabidopsis/metabolismo , Transporte Biológico , Plantas/metabolismo , Estresse do Retículo Endoplasmático , Regulação da Expressão Gênica de PlantasRESUMO
The discovery and application of genome editing introduced a new era of plant breeding by giving researchers efficient tools for the precise engineering of crop genomes1. Here we demonstrate the power of genome editing for engineering broad-spectrum disease resistance in rice (Oryza sativa). We first isolated a lesion mimic mutant (LMM) from a mutagenized rice population. We then demonstrated that a 29-base-pair deletion in a gene we named RESISTANCE TO BLAST1 (RBL1) caused broad-spectrum disease resistance and showed that this mutation caused an approximately 20-fold reduction in yield. RBL1 encodes a cytidine diphosphate diacylglycerol synthase that is required for phospholipid biosynthesis2. Mutation of RBL1 results in reduced levels of phosphatidylinositol and its derivative phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2). In rice, PtdIns(4,5)P2 is enriched in cellular structures that are specifically associated with effector secretion and fungal infection, suggesting that it has a role as a disease-susceptibility factor3. By using targeted genome editing, we obtained an allele of RBL1, named RBL1Δ12, which confers broad-spectrum disease resistance but does not decrease yield in a model rice variety, as assessed in small-scale field trials. Our study has demonstrated the benefits of editing an LMM gene, a strategy relevant to diverse LMM genes and crops.
Assuntos
Diacilglicerol Colinofosfotransferase , Resistência à Doença , Edição de Genes , Oryza , Melhoramento Vegetal , Doenças das Plantas , Resistência à Doença/genética , Edição de Genes/métodos , Genoma de Planta/genética , Oryza/enzimologia , Oryza/genética , Oryza/microbiologia , Fosfatidilinositóis/metabolismo , Melhoramento Vegetal/métodos , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Alelos , Fosfatidilinositol 4,5-Difosfato/metabolismo , Diacilglicerol Colinofosfotransferase/genética , Diacilglicerol Colinofosfotransferase/metabolismoRESUMO
Phosphatidic acid (PA) and lysophosphatidic acid acyltransferases (LPAATs) might be critical for the secretory pathway. Four extra-plastidial LPAATs (LPAAT2, 3, 4, and 5) were identified in Arabidopsis thaliana. These AtLPAATs display a specific enzymatic activity converting lysophosphatidic acid to PA and are located in the endomembrane system. We investigate a putative role for AtLPAATs 3, 4, and 5 in the secretory pathway of root cells through genetical (knockout mutants), biochemical (activity inhibitor, lipid analyses), and imaging (live and immuno-confocal microscopy) approaches. Treating a lpaat4;lpaat5 double mutant with the LPAAT inhibitor CI976 produced a significant decrease in primary root growth. The trafficking of the auxin transporter PIN2 was disturbed in this lpaat4;lpaat5 double mutant treated with CI976, whereas trafficking of H+-ATPases was unaffected. The lpaat4;lpaat5 double mutant is sensitive to salt stress, and the trafficking of the aquaporin PIP2;7 to the plasma membrane in the lpaat4;lpaat5 double mutant treated with CI976 was reduced. We measured the amounts of neo-synthesized PA in roots, and found a decrease in PA only in the lpaat4;lpaat5 double mutant treated with CI976, suggesting that the protein trafficking impairment was due to a critical PA concentration threshold.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Aciltransferases/genética , Aciltransferases/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Ácidos Indolacéticos/metabolismo , Transporte ProteicoRESUMO
A main characteristic of sphingolipids is the presence of a very long chain fatty acid (VLCFA) whose function in cellular processes is not yet fully understood. VLCFAs of sphingolipids are involved in the intracellular traffic to the vacuole and the maturation of early endosomes into late endosomes is one of the major pathways for vacuolar traffic. Additionally, the anionic phospholipid phosphatidylinositol-3-phosphate (PtdIns (3)P or PI3P) is involved in protein sorting and recruitment of small GTPase effectors at late endosomes/multivesicular bodies (MVBs) during vacuolar trafficking. In contrast to animal cells, PI3P mainly localizes to late endosomes in plant cells and to a minor extent to a discrete sub-domain of the plant's early endosome (EE)/trans-Golgi network (TGN) where the endosomal maturation occurs. However, the mechanisms that control the relative levels of PI3P between TGN and MVBs are unknown. Using metazachlor, an inhibitor of VLCFA synthesis, we found that VLCFAs are involved in the TGN/MVB distribution of PI3P. This effect is independent from either synthesis of PI3P by PI3-kinase or degradation of PI(3,5)P2 into PI3P by the SUPPRESSOR OF ACTIN1 (SAC1) phosphatase. Using high-resolution live cell imaging microscopy, we detected transient associations between TGNs and MVBs but VLCFAs are not involved in those interactions. Nonetheless, our results suggest that PI3P might be transferable from TGN to MVBs and that VLCFAs act in this process.
Assuntos
Arabidopsis/metabolismo , Endossomos/metabolismo , Ácidos Graxos/metabolismo , Fosfatos de Fosfatidilinositol/metabolismo , Vias Biossintéticas , Esfingolipídeos/metabolismo , Rede trans-Golgi/metabolismoRESUMO
The lipid composition of organelles acts as a landmark to define membrane identity and specify subcellular function. Phosphoinositides are anionic lipids acting in protein sorting and trafficking at the trans-Golgi network (TGN). In animal cells, sphingolipids control the turnover of phosphoinositides through lipid exchange mechanisms at endoplasmic reticulum/TGN contact sites. In this study, we discover a mechanism for how sphingolipids mediate phosphoinositide homeostasis at the TGN in plant cells. Using multiple approaches, we show that a reduction of the acyl-chain length of sphingolipids results in an increased level of phosphatidylinositol-4-phosphate (PtdIns(4)P or PI4P) at the TGN but not of other lipids usually coupled to PI4P during exchange mechanisms. We show that sphingolipids mediate Phospholipase C (PLC)-driven consumption of PI4P at the TGN rather than local PI4P synthesis and that this mechanism is involved in the polar sorting of the auxin efflux carrier PIN2 at the TGN. Together, our data identify a mode of action of sphingolipids in lipid interplay at the TGN during protein sorting.
Assuntos
Fosfatidilinositóis/metabolismo , Esfingolipídeos/metabolismo , Rede trans-Golgi/metabolismo , Animais , Retículo Endoplasmático/metabolismo , Humanos , Fosfatidilinositóis/genética , Esfingolipídeos/genética , Fosfolipases Tipo C/metabolismo , Rede trans-Golgi/genéticaRESUMO
Eukaryotic cells have developed specialized membrane structures called organelles, which compartmentalize cellular functions and chemical reactions. Recent improvements in microscopy and membrane compartment isolation techniques are now sophisticating our view. Emerging evidences support that there are distinct sub-populations or subdomains, which are spatially and/or temporally segregated within one type of organelle, contributing to specify differential sorting of various cargos to distinct destinations of the cell. In plant cells, the Golgi apparatus represents a main trafficking hub in which entry occurs through a Golgi Entry Core Compartment (GECCO), that remains to be further characterized, and sorting of cargos is mediated through multiple transport pathways with different sets of regulator proteins at the post-Golgi compartment trans-Golgi network (TGN). Both GECCO and TGN are differentiated sub-populations as compared to the rest of Golgi, and moreover, further subdomain formation within TGN is suggested to play a key role for cargo sorting. In this review, we will summarize recent findings obtained on organelle subdomains, and their relationship with cargo entry at and exit from the Golgi apparatus.
RESUMO
Sphingolipids are fundamental lipids involved in various cellular, developmental and stress-response processes. As such, they orchestrate not only vital molecular mechanisms of living cells but also act in diseases, thus qualifying as potential pharmaceutical targets. Sphingolipids are universal to eukaryotes and are also present in some prokaryotes. Some sphingolipid structures are conserved between animals, plants and fungi, whereas others are found only in plants and fungi. In plants, the structural diversity of sphingolipids, as well as their downstream effectors and molecular and cellular mechanisms of action, are of tremendous interest to both basic and applied researchers, as about half of all small molecules in clinical use originate from plants. Here, we review recent advances towards a better understanding of the biosynthesis of sphingolipids, the diversity in their structures as well as their functional roles in membrane architecture, cellular processes such as membrane trafficking and cell polarity, and cell responses to environmental or developmental signals.
Assuntos
Membrana Celular/ultraestrutura , Plantas/metabolismo , Esfingolipídeos/biossíntese , Sequência de Carboidratos , Comunicação Celular , Membrana Celular/química , Polaridade Celular , Plantas/ultraestrutura , Esfingolipídeos/química , Estresse FisiológicoRESUMO
Endosomes play a major role in various cellular processes including cell-cell signaling, development and cellular responses to environment. Endosomes are dynamically organized into a complex set of endomembrane compartments themselves subcompartmentalized in distinct pools or subpopulations. It is increasingly evident that endosome dynamics and maturation is driven by local modification of lipid composition. The diversity of membrane lipids is impressive and their homeostasis often involves crosstalk between distinct lipid classes. Hence, biochemical characterization of endosomal membrane lipidome would clarify the maturation steps of endocytic routes. Immunopurification of intact endomembrane compartments has been employed in recent years to isolate early and late endosomal compartments and can even be used to separate subpopulations of early endosomes. In this section, we will describe the immunoprecipitation protocol to isolate endosomes with the aim to analyze the lipid content. We will detail a procedure to identify the total fatty acid and sterol content of isolated endosomes as a first line of lipid identification. Advantages and limitations of the method will be discussed as well as potential pitfalls and critical steps.
Assuntos
Arabidopsis/citologia , Endossomos/química , Lipídeos de Membrana/análise , Arabidopsis/química , Arabidopsis/metabolismo , Ácidos Graxos/análise , Espectrometria de Massas , Transporte Proteico , Esteróis/análise , Rede trans-Golgi/químicaRESUMO
Membrane lipids are often viewed as passive building blocks of the endomembrane system. However, mounting evidence suggests that sphingolipids, sterols, and phospholipids are specifically targeted by developmental pathways, notably hormones, in a cell- or tissue-specific manner to regulate plant growth and development. Targeted modifications of lipid homeostasis may act as a way to execute a defined developmental program, for example, by regulating other signaling pathways or participating in cell differentiation. Furthermore, these regulations often feed back on the very signaling pathway that initiates the lipid metabolic changes. Here, we review several recent examples highlighting the intricate feedbacks between membrane lipid homeostasis and plant development. In particular, these examples illustrate how all aspects of membrane lipid metabolic pathways are targeted by these feedback regulations. We propose that the time has come to consider membrane lipids and lipid metabolism as an integral part of the developmental program needed to build a plant.
Assuntos
Retroalimentação , Homeostase/fisiologia , Metabolismo dos Lipídeos/fisiologia , Lipídeos de Membrana/metabolismo , Desenvolvimento Vegetal/fisiologia , Redes e Vias MetabólicasRESUMO
In the plant sterol biosynthetic pathway, sterol 4α-methyl oxidase1 (SMO1) and SMO2 enzymes are involved in the removal of the first and second methyl groups at the C-4 position, respectively. SMO2s have been found to be essential for embryonic and postembryonic development, but the roles of SMO1s remain unclear. Here, we found that the three Arabidopsis (Arabidopsis thaliana) SMO1 genes displayed different expression patterns. Single smo1 mutants and smo1-1 smo1-3 double mutants showed no obvious phenotype, but the smo1-1 smo1-2 double mutant was embryo lethal. The smo1-1 smo1-2 embryos exhibited severe defects, including no cotyledon or shoot apical meristem formation, abnormal division of suspensor cells, and twin embryos. These defects were associated with enhanced and ectopic expression of auxin biosynthesis and response reporters. Consistently, the expression pattern and polar localization of PIN FORMED1, PIN FORMED7, and AUXIN RESISTANT1 auxin transporters were dramatically altered in smo1-1 smo1-2 embryos. Moreover, cytokinin biosynthesis and response were reduced in smo1-1 smo1-2 embryos. Tissue culture experiments further demonstrated that homeostasis between auxin and cytokinin was altered in smo1-1 smo1-2 heterozygous mutants. This disturbed balance of auxin and cytokinin in smo1-1 smo1-2 embryos was accompanied by unrestricted expression of the quiescent center marker WUSCHEL-RELATED HOMEOBOX5 Accordingly, exogenous application of either auxin biosynthesis inhibitor or cytokinin partially rescued the embryo lethality of smo1-1 smo1-2 Sterol analyses revealed that 4,4-dimethylsterols dramatically accumulated in smo1-1 smo1-2 heterozygous mutants. Together, these data demonstrate that SMO1s function through maintaining correct sterol composition to balance auxin and cytokinin activities during embryogenesis.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/embriologia , Citocininas/biossíntese , Desenvolvimento Embrionário , Ácidos Indolacéticos/metabolismo , Oxigenases de Função Mista/genética , Arabidopsis/enzimologia , Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Padronização Corporal , Retículo Endoplasmático/metabolismo , Proteínas de Homeodomínio/metabolismo , Raízes de Plantas/embriologiaRESUMO
Lateral root organogenesis plays an essential role in elaborating plant root system architecture. In Arabidopsis, the AP2 family transcription factor PUCHI controls cell proliferation in lateral root primordia. To identify potential targets of PUCHI, we analyzed a time course transcriptomic dataset of lateral root formation. We report that multiple genes coding for very long chain fatty acid (VLCFA) biosynthesis enzymes are induced during lateral root development in a PUCHI-dependent manner. Significantly, several mutants perturbed in VLCFA biosynthesis show similar lateral root developmental defects as puchi-1 Moreover, puchi-1 roots display the same disorganized callus formation phenotype as VLCFA biosynthesis-deficient mutants when grown on auxin-rich callus-inducing medium. Lipidomic profiling of puchi-1 roots revealed reduced VLCFA content compared with WT. We conclude that PUCHI-regulated VLCFA biosynthesis is part of a pathway controlling cell proliferation during lateral root and callus formation.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Calo Ósseo/crescimento & desenvolvimento , Raízes de Plantas/crescimento & desenvolvimento , Fatores de Transcrição/genética , Arabidopsis/crescimento & desenvolvimento , Calo Ósseo/metabolismo , Proliferação de Células/genética , Ácidos Graxos/biossíntese , Ácidos Graxos/genética , Ácidos Indolacéticos/metabolismo , Desenvolvimento Vegetal/genética , Raízes de Plantas/genéticaRESUMO
Root hairs are protrusions from root epidermal cells with crucial roles in plant soil interactions. Although much is known about patterning, polarity and tip growth of root hairs, contributions of membrane trafficking to hair initiation remain poorly understood. Here, we demonstrate that the trans-Golgi network-localized YPT-INTERACTING PROTEIN 4a and YPT-INTERACTING PROTEIN 4b (YIP4a/b) contribute to activation and plasma membrane accumulation of Rho-of-plant (ROP) small GTPases during hair initiation, identifying YIP4a/b as central trafficking components in ROP-dependent root hair formation.
Assuntos
Proteínas de Arabidopsis/fisiologia , Arabidopsis/enzimologia , Genes de Plantas , Proteínas de Membrana/farmacologia , Raízes de Plantas/fisiologia , Proteínas rho de Ligação ao GTP/fisiologia , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/farmacologia , Membrana Celular/fisiologia , Genótipo , Proteínas de Membrana/genética , Proteínas Monoméricas de Ligação ao GTP/fisiologia , Mutação , Fenótipo , Transporte Proteico , Sementes , Rede trans-Golgi/fisiologiaRESUMO
The plasma membrane (PM) is the biological membrane that separates the interior of all cells from the outside. The PM is constituted of a huge diversity of proteins and lipids. In this review, we will update the diversity of molecular species of lipids found in plant PM. We will further discuss how lipids govern global properties of the plant PM, explaining that plant lipids are unevenly distributed and are able to organize PM in domains. From that observation, it emerges a complex picture showing a spatial and multiscale segregation of PM components. Finally, we will discuss how lipids are key players in the function of PM in plants, with a particular focus on plant-microbe interaction, transport and hormone signaling, abiotic stress responses, plasmodesmata function. The last chapter is dedicated to the methods that the plant membrane biology community needs to develop to get a comprehensive understanding of membrane organization in plants.
Assuntos
Membrana Celular/química , Membrana Celular/metabolismo , Fosfolipídeos/química , Fitosteróis/química , Esfingolipídeos/química , Interações entre Hospedeiro e Microrganismos/fisiologia , Microdomínios da Membrana/química , Microdomínios da Membrana/metabolismo , Proteínas de Membrana/química , Proteínas de Membrana/metabolismo , Fosfolipídeos/metabolismo , Fitosteróis/metabolismo , Células Vegetais/química , Células Vegetais/ultraestrutura , Plasmodesmos/química , Plasmodesmos/metabolismo , Esfingolipídeos/metabolismo , Estresse Fisiológico/fisiologiaRESUMO
Lipids are essential components of biological membranes that present a wide diversity in eukaryotic cells. Recent impressive advances in lipid biochemistry and biophysics have enabled a refocus of our view of lipids as functional units for cellular activity. However, the gap between molecular and cellular processes remains to be bridged. Here, 2 papers meet the burden of proof that choline transporters participate in local lipid composition modifications at the trans-Golgi network, an intracellular compartment that serves as the main sorting station in the cell. Localization of choline transporters to this precise compartment could be a way for plant cells to quickly modify the membrane lipid composition and asymmetry during both the allocation of cargos and the recruitment of trafficking machineries into distinct subcellular pathways.
Assuntos
Lipídeos de Membrana/metabolismo , Acetilcolina/metabolismo , Animais , Transporte Biológico , Compartimento Celular , Colina/metabolismo , Humanos , Membranas Intracelulares/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Fosfolipídeos/biossíntese , Estudo de Prova de Conceito , Rede trans-Golgi/metabolismoRESUMO
During early seedling development, the shoot apical meristem is protected from damage as the seedling emerges from soil by the formation of apical hook. Hook formation requires differential growth across the epidermis below the meristem in the hypocotyl. The plant hormones ethylene and auxin play key roles during apical hook development by controlling differential growth. We provide genetic and cell biological evidence for the role of ADP-ribosylation factor 1 (ARF1)-GTPase and its effector ARF-guanine-exchange factors (GEFs) of the Brefeldin A-inhibited GEF (BIG) family and GNOM in ethylene- and auxin-mediated control of hook development. We show that ARF-GEF GNOM acts early, whereas BIG ARF-GEFs act at a later stage of apical hook development. We show that the localization of ARF1 and BIG4 at the trans-Golgi network (TGN) depends on ECHIDNA (ECH), a plant homolog of yeast Triacylglycerol lipase (TLG2/SYP4) interacting protein Tgl2-Vesicle Protein 23 (TVP23). BIGs together with ECH and ARF1 mediate the secretion of AUX1 influx carrier to the plasma membrane from the TGN during hook development and defects in BIG or ARF1 result in insensitivity to ethylene. Thus, our data indicate a division of labor within the ARF-GEF family in mediating differential growth with GNOM acting during the formation phase whereas BIGs act during the hook maintenance phase downstream of plant hormone ethylene.